GUT HEALTH: THE NEW PARADIGM IN FOOD ANIMAL PRODUCTION EDITED BY : Ryan J. Arsenault and Michael H. Kogut PUBLISHED IN : Frontiers in Veterinary Science Frontiers Copyright Statement About Frontiers © Copyright 2007-2016 Frontiers Media SA. All rights reserved. Frontiers is more than just an open-access publisher of scholarly articles: it is a pioneering All content included on this site, such as text, graphics, logos, button approach to the world of academia, radically improving the way scholarly research icons, images, video/audio clips, is managed. The grand vision of Frontiers is a world where all people have an equal downloads, data compilations and software, is the property of or is opportunity to seek, share and generate knowledge. Frontiers provides immediate and licensed to Frontiers Media SA permanent online open access to all its publications, but this alone is not enough to (“Frontiers”) or its licensees and/or subcontractors. The copyright in the realize our grand goals. text of individual articles is the property of their respective authors, subject to a license granted to Frontiers. Frontiers Journal Series The compilation of articles constituting The Frontiers Journal Series is a multi-tier and interdisciplinary set of open-access, online this e-book, wherever published, as well as the compilation of all other journals, promising a paradigm shift from the current review, selection and dissemination content on this site, is the exclusive property of Frontiers. For the processes in academic publishing. All Frontiers journals are driven by researchers for conditions for downloading and researchers; therefore, they constitute a service to the scholarly community. At the same copying of e-books from Frontiers’ website, please see the Terms for time, the Frontiers Journal Series operates on a revolutionary invention, the tiered publishing Website Use. If purchasing Frontiers system, initially addressing specific communities of scholars, and gradually climbing up to e-books from other websites or sources, the conditions of the broader public understanding, thus serving the interests of the lay society, too. website concerned apply. Images and graphics not forming part of user-contributed materials may Dedication to quality not be downloaded or copied Each Frontiers article is a landmark of the highest quality, thanks to genuinely collaborative without permission. Individual articles may be downloaded interactions between authors and review editors, who include some of the world’s best and reproduced in accordance academicians. Research must be certified by peers before entering a stream of knowledge with the principles of the CC-BY licence subject to any copyright or that may eventually reach the public - and shape society; therefore, Frontiers only applies other notices. They may not be re-sold as an e-book. the most rigorous and unbiased reviews. As author or other contributor you Frontiers revolutionizes research publishing by freely delivering the most outstanding grant a CC-BY licence to others to research, evaluated with no bias from both the academic and social point of view. reproduce your articles, including any graphics and third-party materials By applying the most advanced information technologies, Frontiers is catapulting scholarly supplied by you, in accordance with the Conditions for Website Use and publishing into a new generation. subject to any copyright notices which you include in connection with your What are Frontiers Research Topics? articles and materials. All copyright, and all rights therein, Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: are protected by national and international copyright laws. they are collections of at least ten articles, all centered on a particular subject. With their The above represents a summary unique mix of varied contributions from Original Research to Review Articles, Frontiers only. For the full conditions see the Conditions for Authors and the Research Topics unify the most influential researchers, the latest key findings and historical Conditions for Website Use. advances in a hot research area! Find out more on how to host your own Frontiers ISSN 1664-8714 Research Topic or contribute to one as an author by contacting the Frontiers Editorial ISBN 978-2-88945-029-9 DOI 10.3389/978-2-88945-029-9 Office: [email protected] Frontiers in Veterinary Science 1 October 2016 | Gut Health: The New Paradigm in Food Animal Production GUT HEALTH: THE NEW PARADIGM IN FOOD ANIMAL PRODUCTION Topic Editors: Ryan J. Arsenault, University of Delaware, USA Michael H. Kogut, United States Department of Agriculture, Agricultural Research Service, USA Gut health and specifically the gut microbiome-host interaction is currently a major research topic across the life sciences. In the case of animal sciences research into animal production and health, the gut has been a continuous area of interest. Production parameters such as growth and feed efficiency are entirely dependent on optimum gut health. In addition, the gut is a major immune organ and one of the first lines of defense in animal disease. Recent changes in animal production management and feed regulations, both regulatory and consumer driven, have placed added emphasis on finding ways to optimize gut health in novel and effective ways. In this volume we bring together original research and review articles covering three major categories of gut health and animal production: the gut microbiome, mucosal immunology, and feed-based interventions. Included within these categories is a broad range of scientific expertise and experimental approaches that span food animal production. Our goal in bringing together the articles on this research topic is to survey the current knowledge on gut health in animal production. The following 15 articles include knowledge and perspectives from researchers from multiple countries and research perspectives, all with the central goal of improving animal health and production. Citation: Arsenault, R. J., Kogut, M. H., eds. (2016). Gut Health: The New Paradigm in Food Animal Production. Lausanne: Frontiers Media. doi: 10.3389/978-2-88945-029-9 Frontiers in Veterinary Science 2 October 2016 | Gut Health: The New Paradigm in Food Animal Production Table of Contents 05 Editorial: Gut Health: The New Paradigm in Food Animal Production Michael H. Kogut and Ryan J. Arsenault Chapter 1: The Gut Microbiome 09 Blurred Lines: Pathogens, Commensals, and the Healthy Gut Paul Wigley 13 The Gut Microbiome and Its Potential Role in the Development and Function of Newborn Calf Gastrointestinal Tract Nilusha Malmuthuge, Philip J. Griebel and Le Luo Guan 23 Development of the Chick Microbiome: How Early Exposure Influences Future Microbial Diversity Anne L. Ballou, Rizwana A. Ali, Mary A. Mendoza, J. C. Ellis, Hosni M. Hassan, W. J. Croom and Matthew D. Koci 35 Spatial and Temporal Changes in the Broiler Chicken Cecal and Fecal Microbiomes and Correlations of Bacterial Taxa with Cytokine Gene Expression Brian B. Oakley and Michael H. Kogut 47 Temporal Relationships Exist Between Cecum, Ileum, and Litter Bacterial Microbiomes in a Commercial Turkey Flock, and Subtherapeutic Penicillin Treatment Impacts Ileum Bacterial Community Establishment Jessica L. Danzeisen, Jonathan B. Clayton, Hu Huang, Dan Knights, Brian McComb, Shivdeep S. Hayer and Timothy J. Johnson 57 Salmonella enterica Serovars Enteritidis Infection Alters the Indigenous Microbiota Diversity in Young Layer Chicks Khin K. Z. Mon, Perot Saelao, Michelle M. Halstead, Ganrea Chanthavixay, Huai-Chen Chang, Lydia Garas, Elizabeth A. Maga and Huaijun Zhou 73 An Introduction to the Avian Gut Microbiota and the Effects of Yeast-Based Prebiotic-Type Compounds as Potential Feed Additives Stephanie M. Roto, Peter M. Rubinelli and Steven C. Ricke Chapter 2: Mucosal Immune Response 91 Regulation of the Intestinal Barrier Function by Host Defense Peptides Kelsy Robinson, Zhuo Deng, Yongqing Hou and Guolong Zhang 108 Immunometabolism and the Kinome Peptide Array: A New Perspective and Tool for the Study of Gut Health Ryan J. Arsenault and Michael H. Kogut Frontiers in Veterinary Science 3 October 2016 | Gut Health: The New Paradigm in Food Animal Production 113 A Role for the Non-Canonical Wnt-a-Catenin and TGF-a Signaling Pathways in the Induction of Tolerance during the Establishment of a Salmonella enterica Serovar Enteritidis Persistent Cecal Infection in Chickens Michael H. Kogut and Ryan J. Arsenault 124 Effect of Dietary Exogenous Enzyme Supplementation on Enteric Mucosal Morphological Development and Adherent Mucin Thickness in Turkeys Ayuub A. Ayoola, Ramon D. Malheiros, Jesse L. Grimes and Peter R. Ferket 132 Evaluation of Gastrointestinal Leakage in Multiple Enteric Inflammation Models in Chickens Vivek A. Kuttappan, Eduardo A. Vicuña, Juan D. Latorre, Amanda D. Wolfenden, Guillermo I. Téllez, Billy M. Hargis and Lisa R. Bielke 138 Identification of Potential Biomarkers for Gut Barrier Failure in Broiler Chickens Juxing Chen, Guillermo Tellez, James D. Richards and Jeffery Escobar Chapter 3: Feed Microbials and Additives 148 Selection of Bacillus spp. for Cellulase and Xylanase Production as Direct-Fed Microbials to Reduce Digesta Viscosity and Clostridium perfringens Proliferation using an In Vitro Digestive Model in Different Poultry Diets Juan D. Latorre, Xochitl Hernandez-Velasco, Vivek A. Kuttappan, Ross E. Wolfenden, Jose L. Vicente, Amanda D. Wolfenden, Lisa R. Bielke, Omar F. Prado-Rebolledo, Eduardo Morales, Billy M. Hargis and Guillermo Tellez 156 Phytogenic Feed Additives as an Alternative to Antibiotic Growth Promoters in Broiler Chickens Ganapathi Raj Murugesan, Basharat Syed, Sudipto Haldar and Chasity Pender 162 Corrigendum: Phytogenic Feed Additives as an Alternative to Antibiotic Growth Promoters in Broiler Chickens Ganapathi Raj Murugesan, Basharat Syed, Sudipto Haldar and Chasity Pender 163 Corrigendum II: Phytogenic Feed Additives as an Alternative to Antibiotic Growth Promoters in Broiler Chickens Ganapathi Raj Murugesan, Basharat Syed, Sudipto Haldar and Chasity Pender Frontiers in Veterinary Science 4 October 2016 | Gut Health: The New Paradigm in Food Animal Production Editorial published: 31 August 2016 doi: 10.3389/fvets.2016.00071 Editorial: Gut Health: The New Paradigm in Food Animal Production Michael H. Kogut1* and Ryan J. Arsenault2 1 USDA Agricultural Research Service, College Station, TX, USA, 2 University of Delaware, Newark, DE, USA Keywords: gut health, production animals, Chickens, Swine, Cattle, microbiome, mucosal immunity The Editorial on the Research Topic Gut Health: The New Paradigm in Animal Production Optimal gut health is of vital importance to the performance of production animals. Gut health is synonymous in animal production industries with animal health. Although there does appear to be a direct relationship between animal performance and a “healthy” gastrointestinal tract (GIT), there is no clear definition for “gut health” that encompasses a number of physiological and functional fea- tures, including nutrient digestion and absorption, host metabolism and energy generation, a stable microbiome, mucus layer development, barrier function, and mucosal immune responses (1–8). The GIT is responsible for regulating physiological homeostasis that provides the host the ability to withstand infectious and non-infectious stressors (9–19). Understanding the interactions between these diverse physiological features emphasizes the extent of areas encompassed by gut health and the ability to regulate animal production. For our part, we will define gut health as the absence/ prevention/avoidance of disease so that the animal is able to perform its physiological functions in Edited by: order to withstand exogenous and endogenous stressors. Furthermore, worldwide public concerns Mary M. Christopher, about the production animal industries’ dependency on the use of growth-promoting antibiotics University of California Davis, USA (AGPs) have resulted in the ban of AGPs by the European Union and a reassessment of their use in Reviewed by: the United States. Thus, current research is focused on alternatives to antibiotics for sustainable food Mari Smits, animal production (20). Wageningen UR (University & A recent Research Topic in Frontiers in Veterinary Infectious Diseases was on gut health and Research Centre), Netherlands wondering whether we should consider gut health as the new standard when considering animal *Correspondence: production. The objective of this Editorial is not to review the literature on gut health in production Michael H. Kogut animals, but, rather, it is our attempt to summarize findings of the 15 papers that were published [email protected] within this Research Topic. Obviously, the Topic was not comprehensive in the production animal commodity reported, but it was a very good overview of the current status of the ongoing work in Specialty section: gut health and physiology within the veterinary community. This article was submitted to Veterinary Infectious Diseases, a section of the journal GUT MICROBIOME Frontiers in Veterinary Science The complex gut microbiome is not a silent organ or a collection of passenger microorganisms; but Received: 06 July 2016 rather, the intestinal microbial community represents active participants in vertebrate immunity Accepted: 18 August 2016 and physiology. The gut microbiota confers health benefits to the host, including aiding in the Published: 31 August 2016 digestion and absorption of nutrients, contributing to the construction of the intestinal epithelial Citation: barrier, the development and function of the host immune system, and competing with pathogenic Kogut MH and Arsenault RJ (2016) Editorial: Gut Health: The New microbes to prevent their harmful propagation (18, 21). Unlike the host genome, which is rarely Paradigm in Food Animal Production. manipulated by xenobiotic intervention, the microbiome is readily changeable by diet, ingestion of Front. Vet. Sci. 3:71. antibiotics, infection by pathogens, and other life events [Danzeisen et al.; Ballou et al.; Mon et al.; doi: 10.3389/fvets.2016.00071 Malmuthauge et al.; (8)]. Frontiers in Veterinary Science | www.frontiersin.org 5 August 2016 | Volume 3 | Article 71 Kogut and Arsenault Gut Health and Animal Production Antibiotics have a great effect on the host normal microbiota are cost-effective, do not induce antimicrobial resistance in upsetting the balance and inducing a dysbiotic state (8). The use pathogens, and, because of their multiple mechanisms of action, of sub-therapeutic doses of antibiotics in animal diets have been can be used in the variety of environments found in livestock a common practice for promoting growth due to their ability to industries. increase feed efficiency or preventing diseases. Danzeisen et al. used a sub-therapeutic concentration of penicillin to define MUCOSAL IMMUNE RESPONSE beneficial members of the microbiome in turkeys that resulted in increased feed efficiency and enhanced growth. By identifying The intestinal tract is an active immunological organ with more the specific bacterial populations responsible for improved per- resident immune cells than anywhere else in the body. They are formance, the authors hypothesize that these bacteria can then organized in lymphoid structures called Peyer’s patches and iso- be used as probiotics. lated lymphoid follicles, such as the cecal tonsils. Macrophages, The microbiome has a direct effect on the development and dendritic cells, various subsets of T cells, B cells, and secretory function of the mucosal immune system. Malmuthauge et al. IgA all contribute to the generation of a proper immune response found significant associations between the microbiome and to invading pathogens, while keeping the resident microbial the expression of genes regulating the mucosal barrier and community in check without generating an overt inflammatory innate immunity in neonatal cattle. Regional differences in the response. microbiome were associated with regional differences in innate In addition to the immune cells, the intestinal epithelial cells immune gene transcription. Similar findings were described contribute to mucosal immunity (21). A single layer of epithe- between the microbiome of broiler chickens and the expression of lial cells separates the densely colonized and environmentally avian cytokine RNA transcripts (Oakley and Kogut). A negative exposed intestinal lumen from the sterile subepithelial tissue, correlation between pro-inflammatory cytokine genes and the maintains homeostasis in the presence of the enteric microbiota, phylum Firmicutes was found; whereas a positive correlation was and contributes to rapid and efficient antimicrobial host defense identified with the pro-inflammatory cytokines and the phylum in the event of infection with pathogens. Both epithelial antimi- Proteobacteria. crobial host defense and homeostasis rely on signaling pathways Wigley and Ballou et al. asked the questions: what constitutes induced by innate immune receptors demonstrating the active a normal or healthy microbiome and what effects do treatments role of epithelial cells in the host–microbial interplay. Lastly, that are being used to improve gut health (vaccines and probiotics) a layer of mucus overlying the intestinal epithelium forms a have on the development of the gut microbiome? Wigley pointed physical barrier between the mucosa and the resident microbiota, out that certain bacteria, such as Escherichia coli, Clostridium per- minimizing both microbial translocation and excessive immune fringens, and Campylobacter, are often considered commensals activation by the resident microbes. and part of the cecal microbiome. The removal of AGPs, manipu- Intestinal integrity is fundamentally important for the growth lation of the cecal microbiome, changing husbandry practices, and performance of food animals. One of the main advantages and other internal and external factors lead to changes in the host of AGPs in animal feed was the reduction in the low-grade, responses that result in “new” infections (22–25). Using a live food-induced chronic inflammation that would otherwise be attenuated Salmonella vaccine or a lactic acid bacteria probiotic, detrimental to animal growth (27). Removal of AGPs from ani- Ballou et al. characterized the effects of gut health treatments mal feeds results in an increase in enteric disorders, infections, have on the microbiome. Alterations in microbial diversity in and diseases (24, 25, 28, 29). One of the issues with determining the microbiome of young chicks given the vaccine and, to a less dysfunction of the gut barrier is the lack of specific biomarkers. extent with the probiotic, were found, which were independent Two papers in the Research Topic described new methods that: of bacterial colonization by the treatments. The microbiome (a) identify serum and tissue biomarkers of gut barrier function alterations were maintained through 28 days of age, suggesting (Chen et al.) and (b) identify a non-invasive means to measure that early exposure to certain bacteria may permanently influence gut inflammation as a marker of gut leakage (Kuttappan et al.). the microbial diversity in the microbiomes. Similar results were Additionally, Ayoola et al. found that the addition of supplemental described by Mon et al. where a Salmonella infection in day-old enzymes (β-mannanase, a blend of xylanase, amylase, protease) chicks induced a profound decrease in microbial diversity in the to the diet of turkeys reduced food-induced inflammation. cecum. Specifically, there was an increase in Enterobacteriaceae and One of the main immune functions of the epithelial cell sur- a decrease in butyrate-producing bacteria in the Lachnospiraceae face is the production of antimicrobial peptides or host defense family implying that exposure to a Salmonella infection early after peptides [HDPs; Ref. (30)]. HDPs are a diverse group of small hatch can impact the composition of the developing microbiome molecules that possess antimicrobial, immunomodulatory, and that affects colonization resistance to microbial pathogens. barrier function enhancing activities. Robinson et al. described Yeast-derived dietary supplements are increasingly being several classes of small-molecule compounds that induce specific used as pre- and probiotics to improve gut health (26). Roto et al. induction of endogenous HDP. Furthermore, supplementation of detailed the effects of yeast-derived compounds in livestock diets these HDP-inducing compounds enhanced bacterial clearance, and their effect of the microbiome. The use of yeast-derived com- improved enteric barrier integrity, and improved animal produc- pounds as supplements in livestock diets improved performance, tion efficiency with minimal intestinal inflammation. increased beneficial bacteria in the microbiome, and increased The host/pathogen interactome leads to a number of immune responsiveness. Additionally, the yeast-derived products immune and biochemical changes at the infection site as the Frontiers in Veterinary Science | www.frontiersin.org 6 August 2016 | Volume 3 | Article 71 Kogut and Arsenault Gut Health and Animal Production pathogen tries to derive nutrients from the host, while the host A group of natural products known as phytobiotics have been uses immunometabolic countermeasures against the pathogen. the focus of several studies in recent years as antibiotic alterna- Arsenault and Kogut developed a novel tool that characterizes tives (31). Phytobiotics are plant-derived products used in feed the immunometabolic phenotype of infected cells/tissues. The that possess antimicrobial activity, provide antioxidative effects, kinome peptide array identifies alterations in phosphorylation enhance palatability, improve gut functions, and promote growth. events in both immunity and metabolism simultaneously. The Murugesan et al. compared the effects of a commercial phytogenic kinome array was used to identify the immune changes occurring feed additive on growth, intestinal morphology, and microbial in the cecum of chickens during the establishment of a persis- composition in chickens to the effects of an AGP. Improved tent, asymptomatic Salmonella infection (Kogut and Arsenault). growth, increased intestinal villus height, and decreased total A number of immune signaling pathways were activated at the cecal numbers of Clostridium and anaerobic bacteria were site of infection that indicates the development of a tolerogenic comparable between the two treatments. However, birds fed the response allowing the bacteria to establish a persistent infection. phytobiotic additives had a significant reduction in coliforms and an increase in Lactobacillus spp. implying an environment that DIRECT FED MICROBIALS was more suitable for the establishment of growth-promoting bacteria in the microbiome. The increased use of grains as alternative energy sources in poul- Although the GIT is frequently described simply as ‘‘the gut,’’ it try diets has led to an issue with higher levels of less digestible is actually made up of (1) an epithelium; (2) a diverse and robust carbohydrates that result in an increase in digesta viscosity and immune arm, which contains most of the immune cells in the food-induced inflammation. One alternative to optimize digest- body; and (3) the commensal bacteria, which contain more cells ibility of these complex carbohydrates is the inclusion of dietary than are present in the entire host organism. Understanding of enzyme supplements. Latorre et al. took this concept a step the crosstalk between ALL of these interrelated components of further and described the selection of a Bacillus spp. direct fed the gut is what cumulatively makes the gut the basis for the health microbial (DFM) candidate based on their capacity to produce of animals and the motor that drives their performance. enzymes that breakdown these complex carbohydrates. Bacillus spp. that produced cellulose and xylanase were used as DFM and AUTHOR CONTRIBUTIONS were found to reduce digesta viscosity and reduce C. perfringens growth in a number of different diets containing different com- All authors listed have made substantial, direct, and intellectual plex carbohydrates. contribution to the work and approved it for publication. REFERENCES 9. Crhanova M, Hradecka H, Faldynova M, Matulova M, Havlickova H, Sisak F, et al. Immune response of chicken gut to natural colonization by gut micro- 1. Shakouri MD, Iji PA, Mikkelsen LL, Cowieson AJ. Intestinal function and gut flora and to Salmonella enterica serovar enteritidis infection. Infect Immun microflora of broiler chickens as influenced by cereal grains and microbial (2011) 79(7):2755–63. doi:10.1128/IAI.01375-10 enzyme supplementation. J Anim Physiol Anim Nutr (2009) 93(5):647–58. 10. Arsenault RJ, Kogut MH. Salmonella enterica Typhimurium infection causes doi:10.1111/j.1439-0396.2008.00852.x metabolic changes in the chicken muscle involving AMPK, fatty acid and 2. McCracken V, Gaskins H. Probiotics and the immune system. In: Tannock G, insulin mTOR signaling. Vet Res (2013) 44:35. doi:10.1186/1297-9716-44-35 editor. Probiotics: A Critical Review. Helsinki: Horizon Scientific Press (1999). 11. Sansonetti PJ. War and peace at the mucosal surface. Nat Rev Immunol (2004) p. 85–111. 4:953–64. doi:10.1038/nri1499 3. Nurmi E, Nuotio L, Schneitz C. The competitive exclusion concept: devel- 12. Bartlett JR, Smtih MO. Effects of different levels of zinc on the performance opment and future. Int J Food Microbiol (1992) 15(3–4):237–40. doi:10.1016/ and immunocompetence of broilers under heat stress. Poult Sci (2003) 0168-1605(92)90054-7 82:1580–8. doi:10.1093/ps/82.10.1580 4. Beckmann L, Simon O, Vahjen W. Isolation and identification of mixed 13. Garriga C, Hunter RR, Amat C, Planas JM, Mitchell MA, Moreto M. Heat stress linked beta-glucan degrading bacteria in the intestine of broiler chick- increases apical glucose transport in the chicken jejunum. Am J Physiol Regul ens and partial characterization of respective 1,3-1,4-beta-glucanase Integr Comp Physiol (2006) 290:195–201. doi:10.1152/ajpregu.00393.2005 activities. J Basic Microbiol (2006) 46(3):175–85. doi:10.1002/jobm. 14. Hart A, Kamm MA. Mechanisms of initiation and perpetuation of gut 200510107 inflammation by stress. Aliment Pharmacol Ther (2002) 16:2017–28. 5. Qu A, Brulc JM, Wilson MK, Law BF, Theoret JR, Joens LA, et al. Comparative doi:10.1046/j.1365-2036.2002.01359.x metagenomics reveals host specific metavirulomes and horizontal gene trans- 15. Quintero-Fiho WM, Ribeiro A, Ferraz-de-Paula V, Pinheiro ML, Sakai M, fer elements in the chicken cecum microbiome. PLoS One (2008) 3(8):e2945. Sa LRM, et al. Heat stress impairs performance parameters, induces intestinal doi:10.1371/journal.pone.0002945 injury, and decreases macrophage activity in broiler chickens. Poult Sci (2010) 6. Dunkley KD, Dunkley CS, Njongmeta NL, Callaway TR, Hume ME, 89:1905–14. doi:10.3382/ps.2010-00812 Kubena LF, et al. Comparison of in vitro fermentation and molecular 16. Quintero-Fiho WM, Rodrigues MV, Ribeiro A, Ferraz-de-Paula V, microbial profiles of high-fiber feed substrates incubated with chicken cecal Pinheiro ML, Sa LRM, et al. Acute heat stress impairs performance param- inocula. Poult Sci (2007) 86(5):801–10. doi:10.1093/ps/86.5.801 eters and induces mild intestinal enteritis in broiler chickens: role of acute 7. van Der Wielen PW, Biesterveld S, Notermans S, Hofstra H, Urlings BA, van hypothalamic-pituitary-adrenal axis activation. J Anim Sci (2012) 90:1986–94. Knapen F. Role of volatile fatty acids in development of the cecal microflora in doi:10.2527/jas.2011-3949 broiler chickens during growth. Appl Environ Microbiol (2000) 66(6):2536–40. 17. Wideman RF, AL-Rubaye A, Kwan YM, Blankenship J, Lester H, Mitchell KN, doi:10.1128/AEM.66.6.2536-2540.2000 et al. Prophylactic administration of a combined prebiotic and probiotic or 8. Oakley BB, Lillehoj HS, Kogut MH, Kim WK, Maurer JJ, Pedroso A, et al. therapeutic administration of enrofloxacin to reduce the incidence of bacterial The chicken gastrointestinal microbiome. FEMS Microbiol Lett (2014) chrondronecrosis with osteomyelitis in broilers. Poult Sci (2015) 94:25–36. 360(2):100–12. doi:10.1111/1574-6968.12608 doi:10.3382/ps/peu025 Frontiers in Veterinary Science | www.frontiersin.org 7 August 2016 | Volume 3 | Article 71 Kogut and Arsenault Gut Health and Animal Production 18. Maslowski KM, Mackay CR. Diet, gut microbiota and immune responses. 27. Niewald TA. The non-antibiotic anti-inflammatory effect of antimicrobial Nat Immunol (2010) 12:5–19. doi:10.1038/ni0111-5 growth promoters, the real mode of action? A hypothesis. Poult Sci (2007) 19. Choct M, Dersjant-Li Y, McLeish J, Persker M. Soy oligosaccharides and 86:605–9. doi:10.1093/ps/86.4.605 soluble non-starch polysaccharides: a review of digestive, nutritive, and 28. Taira K, Nagai T, Obi T, Takase K. Effect of litter moisture on the development anti-nutritive effects in pigs and poultry. Asian-Australas J Anim Sci (2010) of footpad dermatitis in broiler chickens. J Vet Med Sci (2014) 76:583–6. 23:1386–98. doi:10.5713/ajas.2010.90222 doi:10.1292/jvms.13-0321 20. Seal B, Lillehoj HS, Donovan DM, Gay CG. Alternatives to antibiotics: a sym- 29. Awad WA, Molnár A, Aschenbach JR, Ghareeb K, Khayal B, Hess C, et al. posium on the challenges and solutions for animal production. Anim Health Campylobacter infection in chickens modulates the intestinal epithelial Res Rev (2013) 14:78–87. doi:10.1017/S1466252313000030 barrier function. Innate Immun (2015) 21:151–60. doi:10.1177/17534259 21. Yu LC-H, Wang J-T, Wei S-C, Ni YS. Host microbial interactions and regu- 14521648 lation of intestinal epithelial barrier function: from physiology to pathology. 30. Brogden KA, Ackermann M, McCray PB Jr, Tack BF. Antimicrobial peptides World J Gastrointest Pathophysiol (2012) 15:27–43. doi:10.4291/wjgp.v3.i1.27 in animals and their role in host defences. Int J Antimicrob Agents (2003) 22. Stanley D, Geier MS, Hughes RJ, Denman SE, Moore RJ. Highly variable 22:465–78. doi:10.1016/S0924-8579(03)00180-8 microbiota development in the chicken gastrointestinal tract. PLoS One 31. Windisch W, Schedle K, Plitzner C, Kroismayr A. Use of phytogenic prod- (2013) 8:e84290. doi:10.1371/journal.pone.0084290 ucts as feed additives for swine and poultry. J Anim Sci (2007) 86:E140–8. 23. Guabiraba R, Schouler C. Avian colibacillosis: still many black holes. FEMS doi:10.2527/jas.2007-0459 Microbiol Lett (2015) 362:15. doi:10.1093/femsle/fnv118 24. Humphrey S, Chaloner G, Kemmett K, Davidson N, Williams N, Kipar A, Conflict of Interest Statement: The authors declare that the research was con- et al. Campylobacter jejuni is not merely a commensal in commercial broiler ducted in the absence of any commercial or financial relationships that could be chickens and affects bird welfare. Mbio (2014) 5:e1364–1314. doi:10.1128/ construed as a potential conflict of interest. mBio.01364-14 25. Dumas MD, Polson SW, Ritter D, Ravel J, Gelb J Jr, Morgan R, et al. Impacts Copyright © 2016 Kogut and Arsenault. This is an open-access article distributed of poultry house environment on poultry litter bacterial community composi- under the terms of the Creative Commons Attribution License (CC BY). The use, tion. PLoS One (2011) 6:e24785. doi:10.1371/journal.pone.0024785 distribution or reproduction in other forums is permitted, provided the original 26. Sun X, McElroy A, Webb KE, Seftin AE, Novak C. Broiler performance and author(s) or licensor are credited and that the original publication in this journal intestinal alterations when fed drug-free diets. Poult Sci (2005) 84:1294–302. is cited, in accordance with accepted academic practice. No use, distribution or doi:10.1093/ps/84.8.1294 reproduction is permitted which does not comply with these terms. Frontiers in Veterinary Science | www.frontiersin.org 8 August 2016 | Volume 3 | Article 71 OPINION published: 01 October 2015 doi: 10.3389/fvets.2015.00040 Blurred lines: pathogens, commensals, and the healthy gut Paul Wigley * Institute for Infection and Global Health, University of Liverpool, Liverpool, UK Keywords: chicken, microbiome, gut health, probiotics, commensal, Campylobacter, Clostridium perfringens, Escherichia coli The Chicken Microbiome and Health Detailed studies of the chicken microbiome have emerged in recent years, largely due to the impact of next-generation sequencing (NGS). We increasingly understand how the microbiome is important in health, in development of the gut and the immune system, and in maintenance of homeostasis. Manipulation of the microbiota directly through probiotics or antimicrobials or indirectly through feed and feed additives has long been used by the poultry industry to increase growth rates and feed conversion, to improve gut health, and to reduce the burden of pathogens and, in particular, Edited by: to reduce the load of foodborne zoonotic pathogens such as Salmonella and Campylobacter. We Michael Kogut, can now begin to mechanistically determine how these treatments affect the microbiota and the United States Department of Agriculture, Agricultural Research wider host, and this understanding will allow us to use more targeted approaches in the future. In Service, USA terms of food security, increasing yield is clearly a good thing. However, it is far from clear what represents a “healthy” microbiome, and the lines between what is a “harmless” commensal and what Reviewed by: Haiqi He, is a pathogen are often blurred. As such an understanding of the microbial ecology of the gut and how United States Department of this is affected by manipulation of the microbiome or indeed treatment of “pathogens” is essential Agriculture, Agricultural Research in ensuring that treatments intended to improve health and productivity do not in fact cause more Service, USA problems. Bradley L. Bearson, United States Department of Agriculture, Agricultural Research Is it a Pathogen or a Commensal? Service, USA Rami A. Dalloul, The chicken microbiome consists of around 1,000 bacterial species, though the composition varies Virginia Tech, USA over time, between breeds and lines of birds, between flocks, individuals, and at different sites within *Correspondence: the gut (1–5). Proteobacteria make up a relatively small amount of species in the microbiome, but Paul Wigley among these species are a number that may cause disease in the chicken, notably Escherichia coli [email protected] and Clostridium perfringens, and as such are often considered pathogens (4–6). In contrast, the foodborne zoonotic pathogen Campylobacter jejuni is also found frequently as a component of Specialty section: the cecal microbiome but is often considered to be a “harmless commensal.” However, in reality, This article was submitted to these species can have the properties of either pathogen or commensal depending on the bacterial Veterinary Infectious Diseases, pathotype, host immune status, diet, and coinfection. a section of the journal Of these three exemplars, E. coli has perhaps the least direct impact on gut health. However, Frontiers in Veterinary Science extraintestinal infections are a considerable health problem in both broiler and layer chicken Received: 07 August 2015 production. Isolates associated with disease are termed avian pathogenic E. coli or APEC. Much Accepted: 18 September 2015 effort has been directed at understanding the virulence factors and pathogenesis of APEC, and there Published: 01 October 2015 are clearly a number of pathotypes that can cause disease (7, 8). However, wider analysis of isolates Citation: associated with systemic infection or colibacillosis of broiler chickens and those associated with a Wigley P (2015) Blurred lines: pathogens, commensals, and healthy gut show that disease may be caused by isolates that harbor few, if any, APEC-associated the healthy gut. virulence factors while apparently “commensal” isolates carry numerous virulence factors (9). The Front. Vet. Sci. 2:40. implication is that in many clinical cases of colibacillosis, commensal bacteria act as an opportunistic doi: 10.3389/fvets.2015.00040 pathogen due to host factors, environmental stress, poor management, or as a secondary infection. Frontiers in Veterinary Science | www.frontiersin.org 9 October 2015 | Volume 2 | Article 40 Wigley Pathogens, commensals and gut health As such infections are rarely investigated in detail such as geno- factors such as diets high in non-starch polysaccharides (NSPs; typing of isolates; the more generic term of APEC has become wheat, rye, and barley) or animal proteins that provide favorable associated with all E. coli isolated from diseased chickens rather conditions for the growth of C. perfringens A and stress on birds than those E. coli isolates that are primary pathogens per se. in production (23). Again it is difficult to define C. perfringens as Campylobacter jejuni is the most common cause of foodborne a true gut pathogen, but more of an opportunist that frequently human gastrointestinal infection worldwide. Chicken is the main makes up part of the microbiome. reservoir of infection with around 70% of UK retail chicken contaminated in recent surveys (10, 11). C. jejuni colonizes the Manipulation of the Microbiome: Past and lower gastrointestinal tract of the chicken to a high level and has Future Implications for Gut Health been considered to be a commensal due to the absence of clinical disease in experimental infection studies (12). However, in recent Historically, currently and likely into the future, the chicken years, we have begun to reassess this paradigm. Experimental microbiome has been manipulated perhaps more than any other infection of broiler breeds with C. jejuni leads to an inflammatory vertebrate species through the use of growth-promoting antimi- response and changes to gut structure (13–16). Generally, it would crobials, prebiotic and probiotic treatments, and dietary addi- appear that this inflammation is regulated by IL-10-producing tives (24–27). Feed additives such as enzymes have been used cells, but in some broiler breeds, regulation appears to be dys- to increase productivity. For example, the use of phytases to functional and infection may lead to prolonged inflammation, allow the breakdown of plant phytates to be utilized in diet (28). damage, and diarrhea. Does this mean that C. jejuni is truly a Other additives such as plantain NSPs have been proposed to pathogen of the chicken or more a reflection of dysregulation reduce the burden of infections such as Salmonella (29). The of mucosal immune regulation? Indeed, poor gut health is often use of growth-promoting antimicrobials has been banned in the considered as a problem for broiler chickens. Wet litter, due to European Union since 2006 and their use in the USA is under loose feces mixed with the bedding substrate, and dysbacteriosis increasing pressure due to their role in development of antimicro- are frequent problems in broiler production that affect produc- bial resistance. Not unexpectedly, the use of antimicrobial growth tivity and animal welfare both directly and through resulting promoters affects the composition of the microbiota (30, 31), and problems such as pododermatitis and hock burn (17–19). Modern equally the withdrawal of both growth-promoting and anticoc- broiler chickens have been successfully bred to efficiently convert cidial drugs will lead to change in the microbiota composition grain into protein and grow rapidly, reaching slaughter weight at in commercial flocks. Interestingly, a recent study on drug-free 6–7 weeks of age and we increasingly understand the genetic basis broiler production systems in Canada showed an increase in C. for this (20, 21). This, however, may have consequences; well- perfringens (32). Anecdotally, the increased prevalence of both documented musculoskeletal problems are being addressed, but NE and colibacillosis in Europe has been blamed, at least in part, problems with gut health may be less obvious and harder to deal on the withdrawal of growth promoters. While the overriding with. One may pose the question to what extent are these problems problems associated with the emergence of antimicrobial resis- related to the composition of the microbiota and development tance rightly mean that growth-promoting antibiotics have been of a healthy gut or more a consequence of a defect in their gut or are being withdrawn, it clearly illustrates how the manipulation physiology or immune function? Additionally, to what extent of microbiota can have positive effects on health of the chicken. could inappropriate or poorly regulated responses to the “normal” Equally, we need to be aware that changing the microbiota or microbiota be contributing to poor gut health? The example of modulating host responses that are affected by or effect changes C. jejuni illustrates how the balance in maintaining a healthy gut upon the microbiome may have undesirable effects. In the case is likely to be influenced by a large number of both host and of growth promoters, this was their role in the development of microbial factors. resistant bacteria and potential drug residues in the food chain. Clostridia are a major component of the proteobacteria in the As such a better understanding of microbial ecology and how chicken microbiome (5). Of these species, C. perfringens is the interventions impact on the microbiota and the host is needed most important in poultry health. Variants of C. perfringens are before we adopt such changes wholesale. Manipulation of the associated with the gut of many species, and it can be generally microbiome may be used to improve productivity, although the considered as a commensal. Yet, it may produce toxins associated consequences of removing “detrimental” or enriching “beneficial” with disease including human food poisoning or in necrotic infec- taxa are likely to go beyond improving feed conversion. A per- tions of the gut or deep tissue. In the chicken, the C. perfringens turbed microbiome may reveal commensals as having pathogenic toxin group A has become most associated with necrotic enteritis potential and lead to problems in development of the gut and (NE), these isolates producing alpha and particularly netB toxins immune system and poor gut homeostasis. Manipulation of the (22). Despite C. perfringens producing these toxins being closely gut, the microbiome, and the immune response has all been associated with NE, it had proved very difficult to fulfill Koch’s proposed in reducing the burden of carriage of foodborne bacte- postulates as such isolates are frequently found in healthy birds rial pathogens. Our work on feed supplementation with plantain and reliable experimental infection models for NE based on C. NSP showed successful inhibition of Salmonella invasion (29), but perfringens infection alone have proved hard to develop. This is rather unexpectedly lead to increased colonization of the intesti- largely due to most clinical disease being multifactorial involving nal tract with Salmonella gallinarum. S. gallinarum has evolved predisposing factors such as coinfection particularly with species with several defective metabolic pathways that make it a poor col- of the apicomplexan protozoan parasite Eimeria or due to dietary onizer of the chicken gut, but supplementation with plantain NSP Frontiers in Veterinary Science | www.frontiersin.org 10 October 2015 | Volume 2 | Article 40 Wigley Pathogens, commensals and gut health increased colonization either through a direct nutritional source in productivity or health. Yet, this power needs to be tempered or more likely utilization of breakdown products of microbiota with (often substantial) gaps in our understanding of microbial components (33). Equally immunological manipulation may have ecology within the gut. Can changing the microbiota lead to unexpected consequences. Both colonization of Salmonella and perturbation of gut regulation? As we have seen, there are blurred Campylobacter are accompanied by regulation of innate responses lines between pathogens and commensals, and so can changes to to these bacteria in the gut (13, 34, 35). It has been proposed remove apparent pathogens have negative consequences on other that depletion of the regulatory CD4+ CD25+ T-cell population aspects of gut health or could the promotion of “good bacteria” will enhance clearance and thereby reduce the public health risk lead to emergence of “new pathogens.” The historical example due to these pathogens (36, 37). A downside of this may be of growth-promoting antimicrobials illustrates the point. Their increased inflammation and more significantly loss of regulation use was successful in increasing productivity yet almost certainly to components of the microbiome, again blurring lines between has contributed to antimicrobial resistance (38). Their subsequent pathogen and commensal and leading to poor gut and poor health. withdrawal is now resulting in problems in our faster growing modern broiler chickens. Our understanding of the microbiome Conclusion and its manipulation offers a wealth of opportunities, though may not be without risk. Ultimately, the “take-home” message in this article is that the power of NGS and metagenomic approaches allow us to Funding understand the composition of microbiomes in multiple individ- uals of a livestock species quickly and relatively easily. We can This work was supported by the Biotechnology and Biological associate individual taxa and species with good or poor outcomes Science Research Council though grant number BB/J017353/1. References 13. Humphrey S, Chaloner G, Kemmett K, Davidson N, Williams N, Kipar A, et al. Campylobacter jejuni is not merely a commensal in commercial broiler 1. Oakley BB, Buhr RJ, Ritz CW, Kiepper BH, Berrang ME, Seal BS, et al. Suc- chickens and affects bird welfare. Mbio (2014) 5:e1364–1314. doi:10.1128/mBio. cessional changes in the chicken cecal microbiome during 42 days of growth 01364-14 are independent of organic acid feed additives. BMC Vet Res (2014) 10:282. 14. Awad WA, Smorodchenko A, Hess C, Aschenbach JR, Molnár A, Dublecz doi:10.1186/s12917-014-0282-8 K, et al. Increased intracellular calcium level and impaired nutrient absorp- 2. Schokker D, Veninga G, Vastenhouw SA, Bossers A, de Bree FM, Kaal- tion are important pathogenicity traits in the chicken intestinal epithelium Lansbergen LM, et al. Early life microbial colonization of the gut and intestinal during Campylobacter jejuni colonization. Appl Microbiol Biotechnol (2015) development differ between genetically divergent broiler lines. BMC Genomics 99:6431–41. doi:10.1007/s00253-015-6543-z (2015) 16:418. doi:10.1186/s12864-015-1646-6 15. Awad WA, Aschenbach JR, Ghareeb K, Khayal B, Hess C, Hess M. Campy- 3. Stanley D, Hughes RJ, Moore RJ. Microbiota of the chicken gastrointestinal lobacter jejuni influences the expression of nutrient transporter genes in the tract: influence on health, productivity and disease. Appl Microbiol Biotechnol intestine of chickens. Vet Microbiol (2014) 172:195–201. doi:10.1016/j.vetmic. (2014) 98:4301–10. doi:10.1007/s00253-014-5646-2 2014.04.001 4. Stanley D, Geier MS, Hughes RJ, Denman SE, Moore RJ. Highly variable 16. Awad WA, Molnár A, Aschenbach JR, Ghareeb K, Khayal B, Hess C, et al. microbiota development in the chicken gastrointestinal tract. PLoS One (2013) Campylobacter infection in chickens modulates the intestinal epithelial barrier 8:e84290. doi:10.1371/journal.pone.0084290 function. Innate Immun (2015) 21:151–60. doi:10.1177/1753425914521648 5. Oakley BB, Lillehoj HS, Kogut MH, Kim WK, Maurer JJ, Pedroso A, et al. The 17. Dumas MD, Polson SW, Ritter D, Ravel J, Gelb J Jr, Morgan R, et al. Impacts of chicken gastrointestinal microbiome. FEMS Microbiol Lett (2014) 360:100–12. poultry house environment on poultry litter bacterial community composition. doi:10.1111/1574-6968.12608 PLoS One (2011) 6:e24785. doi:10.1371/journal.pone.0024785 6. Stanley D, Geier MS, Chen H, Hughes RJ, Moore RJ. Comparison of fecal and 18. Taira K, Nagai T, Obi T, Takase K. Effect of litter moisture on the development cecal microbiotas reveals qualitative similarities but quantitative differences. of footpad dermatitis in broiler chickens. J Vet Med Sci (2014) 76:583–6. doi:10. BMC Microbiol (2015) 15:51. doi:10.1186/s12866-015-0388-6 1292/jvms.13-0321 7. Dziva F, Hauser H, Connor TR, van Diemen PM, Prescott G, Langridge GC, 19. van der Hoeven-Hangoor E, Paton ND, van de Linde IB, Verstegen MW, et al. Sequencing and functional annotation of avian pathogenic Escherichia coli Hendriks WH. Moisture content in broiler excreta is influenced by excreta serogroup O78 strains reveal the evolution of E. coli lineages pathogenic for nutrient contents. J Anim Sci (2013) 91:5705–13. doi:10.2527/jas.2013-6573 poultry via distinct mechanisms. Infect Immun (2013) 81:838–49. doi:10.1128/ 20. Davis RV, Lamont SJ, Rothschild MF, Persia ME, Ashwell CM, Schmidt CJ. IAI.00585-12 Transcriptome analysis of post-hatch breast muscle in legacy and modern 8. Guabiraba R, Schouler C. Avian colibacillosis: still many black holes. FEMS broiler chickens reveals enrichment of several regulators of myogenic growth. Microbiol Lett (2015) 362(15). doi:10.1093/femsle/fnv118 PLoS One (2015) 10:e0122525. doi:10.1371/journal.pone.0122525 9. Kemmett K, Humphrey T, Rushton S, Close A, Wigley P, Williams NJ. A 21. Godoy TF, Moreira GC, Boschiero C, Gheyas AA, Gasparin G, Paduan M, longitudinal study simultaneously exploring the carriage of APEC virulence et al. SNP and INDEL detection in a QTL region on chicken chromosome 2 associated genes and the molecular epidemiology of faecal and systemic E. coli associated with muscle deposition. Anim Genet (2015) 46:158–63. doi:10.1111/ in commercial broiler chickens. PLoS One (2013) 8:e67749. doi:10.1371/journal. age.12271 pone.0067749 22. Timbermont L, Haesebrouck F, Ducatelle R, Van Immerseel F. Necrotic enteri- 10. FSA welcomes retailers’ efforts to reduce Campylobacter on chickens. Vet Rec tis in broilers: an updated review on the pathogenesis. Avian Pathol (2011) (2015) 176:639. doi:10.1136/vr.h3270 40:341–7. doi:10.1080/03079457.2011.590967 11. FSA survey puts pressure on retailers to reduce Campylobacter in chickens. Vet 23. Moran ET Jr. Intestinal events and nutritional dynamics predispose Clostridium Rec (2015) 176:243. doi:10.1136/vr.h1187 perfringens virulence in broilers. Poult Sci (2014) 93:3028–36. doi:10.3382/ps. 12. Hermans D, Pasmans F, Heyndrickx M, Van Immerseel F, Martel A, Van 2014-04313 Deun K, et al. A tolerogenic mucosal immune response leads to persistent 24. Kerr AK, Farrar AM, Waddell LA, Wilkins W, Wilhelm BJ, Bucher O, et al. A sys- Campylobacter jejuni colonization in the chicken gut. Crit Rev Microbiol (2012) tematic review-meta-analysis and meta-regression on the effect of selected com- 38:17–29. doi:10.3109/1040841X.2011.615298 petitive exclusion products on Salmonella spp. prevalence and concentration Frontiers in Veterinary Science | www.frontiersin.org 11 October 2015 | Volume 2 | Article 40 Wigley Pathogens, commensals and gut health in broiler chickens. Prev Vet Med (2013) 111:112–25. doi:10.1016/j.prevetmed. gallinarum in the chicken. Lett Appl Microbiol (2015) 60:347–51. doi:10.1111/ 2013.04.005 lam.12377 25. Nava GM, Bielke LR, Callaway TR, Castaneda MP. Probiotic alternatives to 34. Shanmugasundaram R, Selvaraj RK. Regulatory T cell properties of chicken reduce gastrointestinal infections: the poultry experience. Anim Health Res Rev CD4+CD25+ cells. J Immunol (2011) 186:1997–2002. doi:10.4049/jimmunol. (2005) 6:105–18. doi:10.1079/AHR2005103 1002040 26. Babu US, Raybourne RB. Impact of dietary components on chicken immune 35. Withanage GS, Wigley P, Kaiser P, Mastroeni P, Brooks H, Powers C, et al. system and Salmonella infection. Expert Rev Anti Infect Ther (2008) 6:121–35. Cytokine and chemokine responses associated with clearance of a primary doi:10.1586/14787210.6.1.121 Salmonella enterica serovar Typhimurium infection in the chicken and in pro- 27. Pedroso AA, Hurley-Bacon AL, Zedek AS, Kwan TW, Jordan AP, Avellaneda tective immunity to rechallenge. Infect Immun (2005) 73:5173–82. doi:10.1128/ G, et al. Can probiotics improve the environmental microbiome and resistome IAI.73.8.5173-5182.2005 of commercial poultry production? Int J Environ Res Public Health (2013) 36. Shanmugasundaram R, Selvaraj RK. In ovo injection of anti-chicken CD25 10:4534–59. doi:10.3390/ijerph10104534 monoclonal antibodies depletes CD4+CD25+ T cells in chickens. Poult Sci 28. Ptak A, Bedford MR, Swiatkiewicz S, Zyla K, Jozefiak D. Phytase modulates ileal (2013) 92:138–42. doi:10.3382/ps.2012-02593 microbiota and enhances growth performance of the broiler chickens. PLoS One 37. Shanmugasundaram R, Selvaraj RK. Effects of in vivo injection of anti-chicken (2015) 10:e0119770. doi:10.1371/journal.pone.0119770 CD25 monoclonal antibody on regulatory T cell depletion and CD4+CD25− T 29. Parsons BN, Wigley P, Simpson HL, Williams JM, Humphrey S, Salisbury AM, cell properties in chickens. Dev Comp Immunol (2012) 36:578–83. doi:10.1016/ et al. Dietary supplementation with soluble plantain non-starch polysaccharides j.dci.2011.09.015 inhibits intestinal invasion of Salmonella typhimurium in the chicken. PLoS One 38. Soulsby L. Antimicrobials and animal health: a fascinating nexus. J Antimicrob (2014) 9:e87658. doi:10.1371/journal.pone.0087658 Chemother (2007) 60(Suppl 1):i77–8. doi:10.1093/jac/dkm358 30. Pourabedin M, Guan L, Zhao X. Xylo-oligosaccharides and virginiamycin dif- ferentially modulate gut microbial composition in chickens. Microbiome (2015) Conflict of Interest Statement: The author declares that the research was con- 3:15. doi:10.1186/s40168-015-0079-4 ducted in the absence of any commercial or financial relationships that could be 31. Lin J, Hunkapiller AA, Layton AC, Chang YJ, Robbins KR. Response of intesti- construed as a potential conflict of interest. nal microbiota to antibiotic growth promoters in chickens. Foodborne Pathog Dis (2013) 10:331–7. doi:10.1089/fpd.2012.1348 32. Gaucher ML, Quessy S, Letellier A, Arsenault J, Boulianne M. Impact of a drug- Copyright © 2015 Wigley. This is an open-access article distributed under the terms free program on broiler chicken growth performances, gut health, Clostridium of the Creative Commons Attribution License (CC BY). The use, distribution or perfringens and Campylobacter jejuni occurrences at the farm level. Poult Sci reproduction in other forums is permitted, provided the original author(s) or licensor (2015) 94:1791–801. doi:10.3382/ps/pev142 are credited and that the original publication in this journal is cited, in accordance with 33. Parsons BN, Campbell BJ, Wigley P. Soluble plantain nonstarch polysaccha- accepted academic practice. No use, distribution or reproduction is permitted which rides, although increasing caecal load, reduce systemic invasion of Salmonella does not comply with these terms. Frontiers in Veterinary Science | www.frontiersin.org 12 October 2015 | Volume 2 | Article 40 REVIEW published: 23 September 2015 doi: 10.3389/fvets.2015.00036 The gut microbiome and its potential role in the development and function of newborn calf gastrointestinal tract Nilusha Malmuthuge 1 , Philip J. Griebel 2,3 and Le Luo Guan 1 * 1 Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada, 2 Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, SK, Canada, 3 School of Public Health, University of Saskatchewan, Saskatoon, SK, Canada A diverse microbial population colonizes the sterile mammalian gastrointestinal tract during and after the birth. There is increasing evidence that this complex microbiome plays a crucial role in the development of the mucosal immune system and influences newborn health. Microbial colonization is a complex process influenced by a two- Edited by: way interaction between host and microbes and a variety of external factors, including Michael Kogut, Agricultural Research Service, United maternal microbiota, birth process, diet, and antibiotics. Following this initial colonization, States Department of Agriculture, continuous exposure to host-specific microbes is not only essential for development and USA maturation of the mucosal immune system but also the nutrition and health of the animal. Reviewed by: Thus, it is important to understand host–microbiome interactions within the context Christi Swaggerty, United States Department of of individual animal species and specific management practices. Data is now being Agriculture, USA generated revealing significant associations between the early microbiome, development Franck Carbonero, University of Arkansas, USA of the mucosal immune system, and the growth and health of newborn calves. The current *Correspondence: review focuses on recent information and discusses the limitation of current data and the Le Luo Guan, potential challenges to better characterizing key host-specific microbial interactions. We 4-16F Agriculture/Forestry Center, also discuss potential strategies that may be used to manipulate the early microbiome to Department of Agricultural, Food and Nutritional Science, University of improve production and health during the time when newborn calves are most susceptible Alberta, Edmonton, AB T6G 2P5, to enteric disease. Canada [email protected] Keywords: gut microbiota, neonatal ruminants, gut development, mucosal immune system, enteric infections Specialty section: This article was submitted to Introduction Veterinary Infectious Diseases, a section of the journal The in utero sterile mammalian gastrointestinal tract (GIT) is rapidly colonized by an array of Frontiers in Veterinary Science microbiota during and after birth. This process of colonization has been described as a co-evolution Received: 27 July 2015 due to the two-way interaction between host and microbes (1). Host (luminal pH, food retention Accepted: 03 September 2015 time in the gut, and immune defense mechanisms), microbial factors (adhesion, survival mecha- Published: 23 September 2015 nisms under oxygen gradient, and mechanisms to obtain nutrients from the host), and external fac- Citation: tors, such as maternal microbiota, delivery mode, diet, and antibiotic treatment during early life, all Malmuthuge N, Griebel PJ and combine to influence gut colonization (2–4). The initial colonizers (Streptococcus and Enterococcus) Guan LL (2015) The gut microbiome utilize available oxygen in the gut and create the anaerobic environment required for strict anaerobic and its potential role in the development and function of newborn gut residents, such as Bifidobacterium and Bacteroides (2, 5, 6). Bifidobacterium and Bacteroides are calf gastrointestinal tract. two of the main gut bacteria present in the majority of human infants (3) that have a beneficial Front. Vet. Sci. 2:36. impact on mucosal immune system. The presence of Bacteroides in the gut plays a vital role in the doi: 10.3389/fvets.2015.00036 development of immunological tolerance to commensal microbiota (7), while the composition of Frontiers in Veterinary Science | www.frontiersin.org 13 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development FIGURE 1 | Number of publication entries in Medline (PubMed) trend* from 1995 to 2013. (A) Publication entries searched with query “gut colonization.” (B) Publication entries searched with query “gut colonization and human.” (C) Publication entries searched with query “gut colonization and ruminant.” (D) Publication entries searched with query “rumen colonization.” *Medline Trend, URL: http://dan.corlan.net/medline-trend.html. Bifidobacterium in the infant gut is linked to a reduced incidence volatile fatty acids (VFAs) and microbial protein (14). Despite of allergy (8). Therefore, neonatal gut colonization is a crucial numerous human and mouse studies reporting the importance period for the developing gut and naïve immune system (9, 10) of early gut microbiota on host health, there are few attempts and may have long-term health effects (5). Although research to understand the role of early gut/rumen colonization on GIT focused on understanding gut colonization of mammals has development or host health in neonatal ruminants. Furthermore, increased dramatically over the last decade (Figures 1A,B), there rumen/gut development and establishment of the microbiota have are still very few studies focused on domestic livestock species, always been studied as separate aspects of ruminant biology and especially ruminants (Figures 1C,D). Information is extremely there have been few attempts to understand possible interactions limited on ruminant gut colonization, especially when focusing between these two events. on the role of the microbiota in the early development of the GIT during the pre-ruminant period. Therefore, the present review builds on the information available for early colonization of the ruminant GIT to identify challenges in understanding the com- Rumen Colonization in Pre-Ruminants plex interaction between host and microbiome. We also use this Colonization of pre-ruminant rumen was first studied using light information to speculate on possible strategies to engineer the microscopy and Gram-staining to visualize bacteria in the late microbiome and improve ruminant health and production. 1940s (15, 16). In the 1980s, Gerard Fonty started to investigate the establishment of the rumen microbial community in lambs by Gut Microbiota in Ruminants using culture-dependent approaches and was the first to report age-dependent changes in the appearance of different microbial Gut microbes of ruminants, mainly the rumen microbiota, pro- populations (17). Anaerobic bacteria dominate in the rumen of vide 70% of their daily energy requirement via the fermenta- neonatal ruminants by the second day of life (109 CFU/ml of tion of undigestible dietary substrates (11). Therefore, studies in rumen fluid) and the density of cellulolytic bacteria stabilized ruminant gut microbiota have focused mainly on the rumen to (107 CFU/ml of rumen fluid) within the first week of life (17). This understand how this microbiome impacts meat and milk produc- study revealed that the dominant bacterial species in the neonatal tion. Rumen microbiota consists of bacteria, archaea, protozoa, lamb rumen was different from those species colonizing the adult and fungi involved in the fermentation of complex carbohydrates, rumen. When the establishment of other microbial groups was and their composition is influenced by a number of factors. For investigated, their appearance was delayed until after bacteria were example, distinct microbial populations have been identified for established (17). Anaerobic fungi and methanogens appear in the the particle-attached, fluid-associated, and tissue-attached frac- neonatal rumen between 8 and 10 days postpartum (17), while tions of the rumen (12). Rumen microbial composition can also protozoa appear only after 15 days postpartum (18). Furthermore, vary significantly depending on the ruminant species, diet, host comparison of conventionalized lambs with conventionally reared age, season, and geographic region (13). Bacteria dominate the lambs suggested that the establishment of protozoa required a rumen microbiome and contribute mainly to the production of well-established bacterial population (18). Frontiers in Veterinary Science | www.frontiersin.org 14 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development The early rumen microbiota consist of bacterial species from microbial community from birth to weaning. Rumen fluid or Propionibacterium, Clostridium, Peptostreptococcus and Bifidobac- content was used as a proxy for the rumen microbiome and terium genera, while Ruminococcus species dominated the cellu- 16S rRNA amplicon-based sequencing approaches were used to lolytic bacterial population (17). Restricted exposure of lambs to identify and quantify bacteria (21, 27–29). These studies revealed their dams or other animals also delayed the establishment of cel- marked heterogeneity in the rumen bacterial composition of indi- lulolytic bacteria, when compared to lambs reared in close contact vidual animals immediately postpartum, but greater similarity with their dams during the first few weeks of life (19). This obser- in bacterial composition was observed with increasing age (26– vation revealed the important role of early environmental expo- 29). There were, however, a number of discrepancies in terms of sure for the establishment of a host-specific microbiota. Fonty and rumen bacterial composition when comparing among studies. For colleagues have also extended their studies to explore the estab- example, Jami and colleagues (27) reported a higher abundance lishment of tissue-attached (epimural) bacteria in the ovine rumen of Streptococcus belonging to the phylum Firmicutes in 1–3-day- (20). Similar to the fluid-associated community, the complexity old calves. In contrast, Rey and colleagues (28) reported a higher of the epimural community and homogeneity among individu- abundance of Proteobacteria in 2-day-old calves. Furthermore, als increased with increasing age (20). A recent study revealed, both Jami et al. (27) and Rey et al. (28) reported a higher abun- however, that the rumen epimural bacterial community in pre- dance of Bacteroides in rumen fluid at 2 weeks of life, while Li weaned calves differs significantly from the content-associated and colleagues (26) observed a greater abundance of Prevotella in community (21). This observation suggests that host–microbial rumen content. Targeting different variable regions of 16S rRNA interactions might play an important role in defining these two gene (V1/V2 versus V3/V4) for amplicon-based sequencing and distinct microbial communities. differences in the environment, in which these calves were raised, Rumen microbiota has a significant impact on pre-ruminant may have influenced the apparent bacterial composition of rumen management, especially the weaning process, which depends on fluid. rumen development and the ability of the microbiome to ferment A study comparing content-associated versus epimural bacte- complex carbohydrates (22). The presence of VFAs (acetate, pro- rial populations in 3-week-old calves revealed that bacterial phy- pionate, and butyrate) in the rumen plays an important role in lotypes belonging to Bacteroidetes (43.8%) and β-Proteobacteria rumen development, especially the development of rumen papil- (25.1%) dominated the epimural community. In contrast, phy- lae (23). The fermentation of undigestible dietary substrates by lotypes from Bacteroidetes (54.8%) and Firmicutes (29.6%) dom- rumen microbiota is the major source of VFAs in ruminants (11, inated the rumen content-associated community (21). Using 14), and it is generally believed that feeding a solid diet accelerates 16S rRNA amplicon-based sequencing, temporal changes in the this process in pre-ruminants (22). Although the establishment epimural bacterial community have also been reported in goat of rumen microbiota has long been studied and their importance kids during the first 10 weeks of life (30). The predominant Pro- in the rumen development has been suggested, the mechanisms teobacteria (>85%) during the first week of life were gradually by which bacteria influence rumen development remain poorly replaced by an increasing abundance of Bacteroidetes (~10%) defined. Moreover, culture-based studies can only identify around and Firmicutes (>15%) (30). Similar to previous culture-based 10% of the total rumen microbiota, leaving the majority of the approaches, these recent studies have confirmed that dynamic microbiome undefined (24). changes occur in the rumen bacterial community during early Recently, enhanced molecular-based technologies, such as next life, with significant differences between the epimural and fluid- generation sequencing (NGS), provide an excellent platform to associated communities in the pre-weaned rumen. identify both culturable and non-culturable microbes as well as Associated with the age-dependent changes in rumen micro- characterizing their potential functions (25). It is now possible to bial composition (Figure 2), there are also changes in the activ- generate a comprehensive profile of both microbial diversity and ity of the rumen microbiota. These functional changes occur functions and explore potential associations between the micro- in the absence of dietary changes during the first 6 weeks of biome and early rumen development. Using NGS, a comparison life (26). Currently, this is the only study using a metagenomic of the rumen bacteriome and metagenome in 2-week-old and 6- approach to assess the metabolic potential of pre-ruminant rumen week-old calves, fed a milk replacer diet, revealed a taxonomi- microbiome. Li and colleagues (26) revealed that ATP-binding cally and functionally diverse rumen microbiome in pre-ruminant cassette family transporters are more abundant at 2 weeks than calves with significant age-dependent changes (26). This study 6 weeks of age but TonB-dependent receptors are more abundant revealed that Bacteroidetes, followed by Firmicutes and Proteobac- at 6 weeks. Glycoside hydrolases (GH2, GH3, GH42, and GH92), teria, colonized in the rumen content of pre-weaned calves, which which breakdown complex carbohydrates, were also detected in displayed age-dependent variations in their relative abundance. the pre-ruminant rumen, even when the diet did not contain com- For example, the abundance of Bacteroidetes increased from 45.7% plex carbohydrates. These observations suggest that early rumen at 2 weeks to 74.8% at 6 weeks of age, despite calves receiving microbiota has the capacity to ferment dietary fiber prior to being the same diet over time. Such age-related differences were more exposed to this material. Moreover, a recent study investigating prominent at the bacterial genera level, where the predominant the activity of the early rumen microbiome revealed that VFA Prevotella (33.1%) at 2 weeks was replaced by Bacteroides (71.4%) production and xylanase and amylase, enzymes that breakdown at 6 weeks. complex carbohydrates, were active within 2 days postpartum Since the study by Li and colleagues (26), there have been (31). The observed glycoside hydrolase activity, in conjunction further studies analyzing changes in the composition of the rumen with VFA production, reveals establishment of a metabolically Frontiers in Veterinary Science | www.frontiersin.org 15 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development FIGURE 2 | Colonization of neonatal calf rumen/gut, immediately postpartum and within the first 12 weeks of life. active adult-like microbiome in the neonatal rumen prior to expo- Currently, characterization of the rumen microbiota is based sure to appropriate dietary substrates. Thus, the establishment primarily on the sequencing of DNA, which represents both active of metabolically active microbiome may occur along with the and dead microbiota. Therefore, the use of RNA-based metatran- transfer of microbiome from the dam to newborn calf and the scriptome approaches may provide a better understanding of the colonization of a species-specific microbiome. biological activity of the early rumen microbiome. Understanding Diet is one of the main factors that influences the compo- the activity of the rumen microbiota may help designing multi- sition of gut microbiota and may also play an important role disciplinary approaches to engineer the early rumen microbiome in the observed temporal changes of the rumen microbiome in with the objective of promoting both rumen development and neonatal calves (27, 28). The rumen content of 3-week-old calves function that better supports the critical transition that occurs fed milk replacer, supplemented with a calf starter ration (20% when ruminants are weaned. crude protein, 3% crude fat, and 5.7% crude fiber), contained a similar abundance of Prevotella (15.1%) and Bacteroides (15.8%) Intestinal Tract Colonization in Pre-Ruminants (21). Calves that received milk replacer only, however, displayed a Early studies on bacterial colonization of the pre-ruminant intes- shift in the predominant rumen content-associated bacteria from tine focused primarily on pathogenic Escherichia coli in calves Prevotella to Bacteroides (26) within the first 6 weeks of life. Thus, and described the pathogenesis of neonatal diarrhea (34–37). the observed similar abundance of these two bacterial genera in 3- Microscopic imaging revealed that pathogenic E. coli prefer- week-old calves fed milk supplemented with calf starter suggests ably attached to and effaced the mucosal epithelium in the that the age-dependent shift in the dominant bacteria may have ileum and large intestine, but not the duodenum and jejunum been triggered by the dietary supplement that contained fiber. of neonatal calves (36). Feeding of probiotic strains isolated In general, it is believed that the introduction of solid diet plays from the intestine of calves reduced enteric colonization of a key role in promoting the establishment of rumen microbiota pathogenic E. coli O157:H7 in pre-weaned calves (38). Further- as milk bypasses the rumen to enter the abomasum (22). More- more, the administration of Bifidobacterium and Lactobacillus to over, pre-weaning diet and feeding methods have been reported newborn calves during the first week of life increased weight to have more pronounced and long-lasting impacts on rumen gain and the feed conversion ratio, while decreasing diarrhea microbial composition (29, 32, 33). Altering feeding practices incidences (39). These effects were most pronounced in pre- during the pre-weaning period were reported to significantly alter weaned calves than weaned calves (39), suggesting the probi- methanogen composition after weaning (32) as well as the density otic supplements are more effective when the gut microbiota is of bacteria and protozoa in pre-weaned lambs (33). Therefore, being established and less effective when the microbiome has managing pre-weaning feeding may be as important as managing stabilized. feeding during the weaning period in terms of microbiota estab- Supplementation of Lactobacillus in young calves was lishment as well as development of the microbial fermentation also reported to increase the total serum immunoglobulin capacity of the rumen. G concentration (40), providing evidence of a host–microbiome Frontiers in Veterinary Science | www.frontiersin.org 16 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development interaction that may influence calf health. More recently, independent approaches (21, 45, 48, 49). When bacterial pop- supplementation of newborn calves with prebiotics (galactooligo ulations throughout the GIT of 20-week-old calves were ana- saccharides) was associated with an increased abundance of lyzed, Bifidobacterium and Lactobacillus displayed greater sur- Lactobacillus and Bifidobacterium in the colon of 2-week-old vival of stomach passage than coliforms and E. coli (45). The calves (41). However, this effect was less pronounced in 4-week- density of these beneficial bacteria was high throughout all GIT old calves (41), suggesting that as with probiotics, it may be easier regions (rumen, abomasum, duodenum, jejunum, cecum, and to manipulate the microbiome during the early colonization colon) of the 20-week-old calves (45). Using culture-independent period (39). In an attempt to reduce antibiotic usage during the approaches, higher bacterial phylotype richness was observed in pre-weaning period, studies continue to investigate the impact the rumen and large intestinal regions than the small intestinal of both probiotics and prebiotics on calf growth and health (42). regions of lambs and calves (21, 48, 49). Collado and Sanz (48) The full impact of these approaches on gut microbial colonization reported, however, a similar bacterial richness throughout the and composition throughout the pre-ruminant period has yet GIT, when using a culture-dependent approach. This observation to be understood and studies are lacking on how altering the is consistent with there being many more unculturable bacterial gut microbiome may impact mucosal immune defenses in species in the rumen and large intestine than the small intes- the GIT. tine. A longer retention time, higher availability of nutrients, and In 1965, Williams Smith used culture-dependent approaches reduced scrutiny by the host mucosal immune system have all for the first time to study bacterial colonization in the pre- been suggested to contribute to the increase in bacterial diversity ruminant GIT, beginning immediately postpartum. He reported and density in the rumen and large intestine of mammals (1). colonization by E. coli and Streptococcus in all gut regions (stom- When bacterial composition throughout the GIT is explored, ach, small intestine, and cecum) of calves within 8 h after birth, the rumen and large intestinal regions consist primarily of Bac- while Lactobacillus colonization was only observed 1 day after teroidetes and Firmicutes, while >95% of the bacteria in the small birth. Lactobacillus then predominated throughout all regions intestine contents are composed of Firmicutes (21). In contrast, of the GIT tested within the first week (43). Bacteroides were the mucosa-associated bacterial community in the small intes- observed only in the cecum and feces after the second day tine is composed of primarily Bacteroidetes, Firmicutes, and Pro- of life (43). The colonization of Clostridium perfringens, previ- teobacteria, including 17 genera that are unique to this region ously known as Clostridium welchii, was also observed in the of the GIT (21). The presence of bacteria unique to the small cecum within 8 h after birth; however, it was not detected in intestine (21) suggests that fecal sample-based studies do not other gut regions until 18 h after birth (43). This study sug- reveal the true GIT microbiome and may not reveal important gested that the newborn GIT was first colonized by facultative regional host–microbial interactions. A recent study in human anaerobes, which then created the anaerobic conditions required infants reported similar observations and it was also concluded for colonization by obligate anaerobic gut microbiota, such as that feces was not representative of host–microbiota interactions Lactobacillus and Bacteroides. A similar evolution of bacterial throughout the gut (50). colonization of the GIT has been reported for other newborn There is increasing evidence that mucosa-attached microbiota mammals (6). are significantly different from those associated with ingesta and Subsequent studies have revealed a higher abundance of Bifi- present in the intestinal lumen. Collado and Sanz (48) first dobacterium and Lactobacillus in fecal samples and throughout studied mucosa-attached bacteria and reported that Bifidobac- the GIT of newborn calves (44, 45). A higher abundance of Bifi- terium and Lactobacillus were predominant throughout the GIT dobacterium in 3–7 days old calves was also associated with a lower (rumen, duodenum, and colon) of calves (9–11 months) and abundance of E. coli (44). More recently, culture-independent lambs (6–9 months). They did not, however, compare mucosa- approaches have been employed to better understand the diversity associated versus intestinal content communities. Studies by Mal- and abundance of bacteria throughout the neonatal ruminant GIT muthuge and colleagues (21, 49) compared mucosa-attached and (46, 47). RNA-based, sequence-specific rRNA cleavage analysis content-associated bacterial communities throughout the GIT of bacteria throughout the first 12 weeks postpartum revealed a of calves and reported that at 3 weeks of life, distinct mucosa- higher abundance of the Bacteroides–Prevotella and Clostridium attached bacterial phylotypes had been established. Furthermore, coccoides–Eubacterium rectale groups in the feces of dairy calves bacterial richness in mucosa-attached communities, especially in (46). Faecalibacterium was one of the most abundant bacteria the ileum, was higher than the content-associated community in 1-week-old calves (21.7%), but then declined with increasing (49). These distinct and richer mucosa-attached bacterial commu- calf age (46). Ruminococcus flavefaciens and Fibrobacter, fibrolytic nities were subsequently confirmed by using pyrosequencing of bacteria, were only observed after 5 weeks postpartum, while 16S rRNA gene amplicons (21). Although the majority of mucosa- Streptococcus and Lactococcus could not be detected after the fifth attached bacteria could not be assigned at a genus level, the use week (46). These studies confirmed that there were significant age- of a NGS approach provided a greater understanding of region- dependent changes in the composition of the GIT microbiome (rumen, small intestine, and large intestine) and sample type- and revealed substantial differences between the rumen and lower (content and mucosa) specific bacteria throughout the GIT of GIT microbiome. pre-weaned calves (21). Regional variations in bacterial phylotypes richness, diver- Based on the previously cited studies, it is clear that the compo- sity, density, and composition throughout the GIT of newborn sition, diversity, and richness of rumen and intestinal microbiota calves have been described, using both culture-dependent and in pre-weaned ruminants can vary depending on various factors, Frontiers in Veterinary Science | www.frontiersin.org 17 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development TABLE 1 | Factors influencing pre-weaned calf rumen/gut microbiota. The presence of gut microbiota in mice is also necessary for the development of secondary lymphoid structure, such as Factor Study Peyer’s patches (PPs), mesenteric lymph nodes, and isolated Age (17, 26–28, 30, 46, 47, 49) lymphoid follicles (54). The establishment of host-specific micro- Diet (colostrum, calf starter) (28, 29, 32, 33, 46, 51, 52) biota, especially bacterial species belong to phylum Firmicutes, is Feeding method (suckling, bottle feeding) (53) essential for the development of a variety of intestinal immune Probiotic, prebiotics (39, 41) Exposure to dam (19, 53) cells (57). For example, when human microbiota colonized the Sample site (21, 43, 48, 49) mouse intestine there were low numbers of CD4+ and CD8+ Sample type (fluid, content, mucosa) (20, 21, 49) T cells, and fewer proliferating T cells and dendritic cells when Host (individuality) (27) compared to mice colonized with mouse microbiota (57). Inter- Infections (47) estingly, the immune cell profile of human microbiota colonized mice was similar to that of germfree mice (57), suggesting the such as age, diet, feeding method, feed additives, sampling loca- presence of a host-specific microbiota is fundamental for mucosal tion (content, mucosa, and feces), and gut region (rumen, large immune system development. Thus, host–microbial interactions intestine, and small intestine) (Table 1; Figure 2). Furthermore, in the developing gut of newborn animals must be studied within variation in microbial composition among individual animals is relevant host species to accurately understand the role of early higher in young than adult ruminants (27). The high variation in microbiota on gut development. bacterial diversity and density (27, 49) among individual rumi- In ruminants, development of mucosa-associated lymphoid nants during early life also suggests that the gut microbiome may tissues (MALTs) in the GIT begins in utero and there is active be more easily changed at this time of life than in adults. This proliferation of B cells in lymphoid follicles of the PP in the may explain why probiotics and prebiotics have been reported complete absence of the gut microbiome (58, 59). Furthermore, to have a much greater effect in young animals than older calves oral delivery of antigens in utero has confirmed that these MALTs (39, 41). Of particular interest are the recent studies conducted by are fully functional and can generate specific immune responses Abecia and colleagues, which revealed long-lasting consequences with the production of secretory IgA (60). In the absence of an when dietary interventions were used to manipulate the rumen in utero infection, however, the appearance of IgG+ and IgA+ cells microbiota in young calves. Thus, a much greater understanding in PPs is delayed until after birth (59). Since immunoglobulin class of early gut microbial colonization and the factors influencing switching occurs in the germinal centers of PPs (54), this suggests establishment of microbiota may provide the basis for rational that the full development of germinal centers requires exposure strategies to manipulate the gut microbiome and improve the to the gut microbiota. However, information regarding the role of growth and health of ruminants throughout the entire production the gut microbiota in the early postnatal development of MALT cycle. in ruminants is scarce. There is a single report that preventing exposure of the ileal PPs to gut microbiome results in premature involution of lymphoid follicles in the PPs of newborn lambs Influence of Microbiome on Gut (61). However, restoration of the gut microbiome at 4 weeks after Development and Mucosal Immune birth reversed lymphoid follicle involution in the ileal PPs (61). Functions Thus, the gut microbiome appears to provide critical signals that maintain the production of the pre-immune B cell repertoire. It Gut microbiota are essential for the development and differ- remains to be determined whether specific microbial species may entiation of the intestinal mucosal epithelium as well as the influence the selection of this immunoglobulin repertoire or if mucosal immune system (54). Most of our knowledge regarding this interaction is restricted to an interaction with innate immune host–microbiome interactions in the GIT has been obtained from receptors. a variety of mouse models. Comparisons between gnotobiotic The host uses pattern recognition receptors, such as toll-like and conventionally reared mice revealed decreased development receptors (TLRs), to recognize the commensal microbiota and of the intestinal epithelium and the mucosal immune system in maintain intestinal homeostasis (62). Activation of TLR signal- the absence of gut microbiota. Thickness of the mucus barrier is ing by intestinal tissue invading pathogens generally stimulates reduced in germfree mice, but administration of microbe-derived inflammatory responses. In contrast, commensal microbiota acti- lipopolysaccharides and peptidoglycans to the colonic mucosal vation of TLR signaling promotes the production of interleukin surface stimulated mucus production and within 40 min restored 6 and tumor necrosis factor that protect intestinal epithelial cells the thickness of the mucus layer to that of conventional mice (55). against injury (62). Therefore, commensal microbial recognition This observation supports the conclusion that the gut microbiota by mucosal TLRs is crucial for the maintenance of intestinal is essential for the secretion of intestinal mucus, an important homeostasis and protection of the gut from injuries. The expres- physical barrier throughout the GIT. In addition, the generation sion of TLRs in the blood of infants (63) was downregulated rate of epithelial cells in germfree mice is lower than that of with increasing age, while memory T cells, such as CD4+ and the conventionally raised mice (56), revealing the importance of CD8+ , increased in number (63). These changes are consistent gut microbiota for maintaining intestinal epithelial cells prolif- with a decrease in innate immune responses that is balanced eration and ensuring recovery of the mucosal barrier following by an increase in adaptive immune responses with increasing injuries. age. Downregulation of innate immune responses with increasing Frontiers in Veterinary Science | www.frontiersin.org 18 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development age has been suggested as one mechanism by which the host associated with increased weight gain in healthy calves, while a avoids unnecessary inflammatory responses to commensal micro- high abundance of Faecalibacterium during the first week of life biota (63). Similar results have been reported when analyzing the was associated with a lower incidence of diarrhea in calves after the intestinal immune system of calves (64, 65). The expression of fourth week of life (47). Thus, it is difficult to determine if changes mucosal TLR genes was downregulated in weaned calves when in the fecal microbiome were a consequence of prior disease and compared to pre-weaned calves (65). In contrast, total leuko- associated therapeutic interventions or if colonization of the GIT cytes including, CD3+ , CD4+ , and CD8+ T cells, increased by specific commensal bacteria had a beneficial effect in terms of in the jejunal and ileal mucosa of calves with increasing age disease resistance. (64). Moreover, a negative correlation was observed between Uyeno and colleagues (46) also reported a high abundance the expression of mucosal TLRs and mucosa-attached bacteria, of Faecalibacterium in the feces of 1-week-old calves and their suggesting a possible link between the gut microbiota and the abundance was higher in the large intestine compared to the small observed age-related changes in the mucosal immune responses intestine of 3-week-old calves (21). Faecalibacterium prausnitzii, (65). However, the mechanism by which gut microbiome col- one of the main butyrate producers in the large intestine, dis- onization affects this shift of mucosal and systemic immune played a negative association with calf diarrhea incidences (47), responses from innate to adaptive remains to be defined. There is, suggesting the high prevalence of this species during early life however, emerging evidence that microbial colonization is asso- may decrease susceptibility to enteric infections. F. prausnitzii ciated with substantial changes in the transcriptome of the bovine also plays a pivotal role in maintaining intestinal homeostasis intestine during the first week of life (66). Transcriptome changes by promoting anti-inflammatory responses and has been shown occurred at the level of miRNA and significant correlations were to decrease in prevalence in patients with inflammatory bowel identified between the gut microbiome and these transcriptome disease (68). Inflammatory bowel disease was also associated with changes. a reduced prevalence of Bifidobacterium (68), suggesting that these Experiments with the mouse model have clearly demonstrated two bacterial groups may have important roles in maintaining the importance of gut microbiota in the development of both intestinal homeostasis and preventing enteric infections. Thus, it innate and adaptive components of the mucosal immune sys- will be important to further explore the potential role of such tem as well as development and maintenance of the intesti- beneficial bacteria in the early gut development and their capacity nal epithelial barrier. Increased susceptibility to enteric infec- to promote host health. tions in gnotobiotic and antibiotic treated mice may also be Poor management of colostrum feeding in newborn calves due to the underdeveloped mucosal immune system and epithe- is one of the main triggers of neonatal calf diarrhea. Feed- lial barrier (54). The immunologically naïve neonatal GIT and ing calves with highly contaminated (bacteria > 106 CFU/ml, the colonizing microbiota undergo a rapid co-evolution during coliform > 103 CFU/ml) and of low quality (IgG < 50 mg/ml) early life and these interactions may be crucial in determin- colostrum (69), poor surveillance of calves born at night, and ing the susceptibility of the neonate to enteric infections. Pre- relying on dams to feed colostrum (70) are some of the major weaned ruminants are highly susceptible to a variety of viral risk factors currently contributing to poor neonatal calf health and bacterial enteric infection within the first few weeks of life in the North American dairy industry. Although the importance (67). Therefore, a thorough understanding of early gut micro- of timed feeding of high quality colostrum for passive trans- biota and its role in regulating and directing early development fer of immunity has been well studied (71), the influence of of the mucosal immune system is essential to improving the colostrum on gut microbial establishment and susceptibility to health of young calves and reducing susceptibility to enteric enteric infection in young ruminants is not clearly understood. A infections. recent study revealed that feeding colostrum within 1 h postpar- tum facilitated bacterial colonization of the small intestine within The Commensal Microbiome and the first 12 h postpartum. Calves-fed colostrum achieved bacterial Enteric Infections in Young Ruminants numbers similar to older calves [1010 16S rRNA gene copy/g of intestinal sample (49)], but significantly fewer bacteria were Neonatal diarrhea is the major cause of death in pre-weaned observed in the intestine of calves deprived of colostrum (52). calves and accounts for >50% of calf deaths in the dairy indus- Furthermore, when comparing to colostrum-deprived calves at try (67). Establishment of the gut microbiome within the first 12 h postpartum, there was a significant increase in the prevalence 7 weeks of life and an association with calf health and growth of Bifidobacterium and a decreased prevalence of E. coli in the (neonatal diarrhea, pneumonia, and weight gain) was recently mucosa-attached communities of calves fed either heat-treated reported (47). Bacterial diversity was lower in calves with pneu- or fresh colostrum (52). Changes in the abundance of mucosa- monia and neonatal diarrhea when compared to healthy calves attached Bifidobacterium and E. coli populations were most pro- (47), suggesting a possible link between gut microbiota and host nounced when calves were fed heat-treated colostrum versus fresh health. The authors speculate that antibiotic treatment may have colostrum (52). Heat treatment (60°C, 60 min) decreases the den- been one factor influencing the gut microbiome in pneumonic sity of total bacteria including pathogens present in colostrum, calves. Furthermore, colonization by enteric pathogens may be which has been suggested to decrease neonatal diarrhea in calves responsible for the observed dysbiosis in gut microbiota during (71). The results from Malmuthuge and colleagues (52), however, neonatal diarrhea (47). Increased fecal bacteria diversity was also suggest that timed feeding of high quality colostrum has a direct Frontiers in Veterinary Science | www.frontiersin.org 19 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development effect on bacterial colonization of the bovine small intestine, in sampling location, the type of sample collected, extraction meth- particular the mucosa-attached community that is in close contact ods, sequencing depth, and the analysis pipeline used. In addition, with the host mucosal immune system. Establishing a bacterial the taxonomic and functional identification of the rumen/gut population dominated by beneficial bacteria may suppress col- microbiome is dependent on existing databases and identified onization of enteropathogens (72) immediately postpartum and organisms and functions are remaining unclassified at lower tax- provide protection against enteric infections in young ruminants onomic levels and at the level of protein coding genes. Single cell with a naïve immune system. Further investigations are necessary genome sequencing and more comprehensive databases for the to also understand how a Bifidobacterium-dominated early gut ruminant gut microbiome are vital to understanding their role in microbiome may influence host performances (weight gain, resis- host development. tance to enteric infections) within the first few weeks and identify A substantial step forward in being able to explain the role the mechanisms by which the commensal microbiome alter both of the gut microbiome in host physiology would be to under- enteric health and general physiology. stand the metabolic capacity of the early microbiome. Metabolic functions of the rumen microbiota appear to be highly redun- Manipulation of the Early Gut Microbiome dant, which may be essential to ensure optimum fermentation to Improve Health and Production of ingested substrates. Therefore, isolation of metabolically active rumen microbiota may be important to further our understand- Manipulation of gut microbiota by feeding microbes, probiotics, ing of their roles in monocultures and mixed populations. This or prebiotics has been widely studied in livestock animals as information will provide the basis for future strategies designed a strategy to improve production and health through altering to manipulate the microbiome and improve both production and rumen fermentation and preventing pathogen colonization (24, health. 42). Direct-fed microbials have been shown to decrease rumen Finally, there is a substantial need to develop ruminant ani- acidosis in cattle, increase milk production in cows, and decrease mal models that can be used to investigate the effects of con- fecal shedding of E. coli in calves (73). These direct-fed micro- trolled changes in the gut microbiome on both host mucosal bials may prevent enteropathogen colonization of the gut by immunity and host metabolism. The rearing of gnotobiotic calves either competing for nutrients, space in the gut environment, is limited by large technical and financial barriers and to date or producing antimicrobial substances (73). Megasphaera elsdenii studies have been limited to changes in diet or the feeding of modifies ruminal fermentation and decreases ruminal acidosis pre- or probiotics and subsequent sampling of rumen or fecal by utilizing lactic acid produced in the rumen (73). However, microflora. The challenge is to develop animal models that allow most of these outcomes are limited to a relatively short interval us to ask questions regarding microbiome changes within spe- following feeding (24) or are effective only in pre-weaned calves cific regions of the GIT and to analyze local effects on mucosal (39), suggesting that these manipulations are either temporary immune and barrier function. The use of a surgically isolated or need to be instituted within a defined developmental period. intestinal segment model in fetal lambs (61) provided an elegant Moreover, it is essential to know how the autochthonous gut model system to create a localized gnotobiotic environment in microbial population responds to these dietary manipulations and the GIT of a developmentally normal animal. A similar model how their compositional changes influence overall gut metabolic system was developed in newborn calves to study the effects and immune functions. It may also be important to determine if of a persistent enteric bacterial infection (74). Thus, it should developing probiotics or direct-fed microbials, based on Faecal- now be possible to manipulate local exposure to the microbiome ibacterium and Bifidobacterium that have already been linked to and analyze the effects on neonatal mucosal immune system calf health, provides a more effective or long-lasting effect. The and barrier development. A critical question to be addressed is establishment of host-specific bacteria is crucial for the develop- whether dysbiosis of the microbiome during colonization of the ment of mucosal immune system, especially for the differentiation newborn GIT has long-term effects, both locally in the GIT and and proliferation of T cell populations (57). Thus, there would be systemically, that impacts the health and production of animals. If substantial value in both isolating and testing bacteria within the long-term effects are observed, then it will be important to deter- same host species that might provide the basis for the developing mine if restoration of the complex microbiome, or specific bac- microbial manipulation techniques. terial species, can effectively reverse the effects of early microbial dysbiosis. Conclusion Acknowledgments Interactions between host and gut microbiota have been explored extensively in humans and mice but these investigations are still The authors appreciate the financial support from Agriculture and in their infancy in ruminants (Figure 1). However, the studies Food Council, Alberta Livestock Industry Development Fund, reviewed to date are generating promising results, describing Alberta Milk, Alberta Livestock and Meat Agency Ltd. (Grant GIT microbial composition (Figure 2) and functions in greater number: 2011F129R), and Natural Sciences and Engineering depth and identifying factors that significantly influence micro- Research Council of Canada (NSERC Discovery Grant). PG is the bial establishment. It is also notable that recent results are based holder of a Tier I CRC in Neonatal Mucosal Immunology, which primarily on nucleic acid sequencing, which may be limited by is funded by the Canadian Institutes of Health Research (CIHR). Frontiers in Veterinary Science | www.frontiersin.org 20 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development References 22. Heinrichs J. Rumen development in the dairy calf [abstract]. Adv Dairy Technol (2005) 17:179–87. Abstract retrieved from western Canadian Dairy Seminar 1. Van den Abbeele P, Van de Wiele T, Verstraete W, Possemiers S. The host 2005 proceedings. selects mucosal and luminal associations of coevolved gut microorganisms: 23. Lane BA, Jesse BW. Effect of volatile fatty acid infusion on development of the a novel concept. FEMS Microbiol Rev (2011) 35:681–704. doi:10.1111/j.1574- rumen epithelium in neonatal sheep. J Dairy Sci (1997) 80:740–6. doi:10.3168/ 6976.2011.00270 jds.S0022-0302(97)75993-9 2. Fanaro S, Chierici R, Guerrini P, Vigi V. Intestinal microflora in early infancy: 24. Weimer PJ. Redundancy, resilience, and host specificity of the ruminal micro- composition and development. Acta Paediatr Suppl (2003) 91:48–55. biota: implications for engineering improved ruminal fermentations. Front 3. Penders J, Thijs C, Vink C, Stelma FF, Snijders B, Kummeling S, et al. Factors Microbiol (2015) 6:296. doi:10.3389/fmicb.2015.00296 influencing the composition of the intestinal microbiota in early infancy. Pedi- 25. McCann JC, Wickersham TA, Loor JJ. High-throughput methods redefine atrics (2006) 118:511–21. doi:10.1542/peds.2005-2824 the rumen microbiome and its relationship with nutrition and metabolism. 4. Adlerberth I, Wold AE. Establishment of the gut microbiota in western infants. Bioinform Biol Insights (2014) 8:109–25. doi:10.4137/BBI.S15389 Acta Paediatr (2009) 98:229–38. doi:10.1111/j.1651-2227.2008.01060 26. Li RW, Connor EE, Baldwin RL, Sparks ML. Characterization of the rumen 5. Conroy ME, Shi HN, Walker WA. The long-term health effects of neonatal microbiota of pre-ruminant calves using metagenomic tools. Environ Microbiol microbial flora. Curr Opin Allergy Clin Immunol (2009) 9:197–201. doi:10.1097/ (2012) 14:129–39. doi:10.1111/j.1462-2920.2011.02543 ACI.0b013e32832b3f1d 27. Jami E, Israel A, Kotser A, Mizrahi I. Exploring the bovine rumen bacterial 6. Jost T, Lacroix C, Braegger CP, Chassard C. New insights in gut microbiota community from birth to adulthood. ISME J (2013) 7:1069–79. doi:10.1038/ establishment in healthy breast fed neonates. PLoS One (2012) 7:e44595. doi: ismej.2013.2 10.1371/journal.pone.0044595 28. Rey M, Enjalbert F, Combes S, Cauquil L, Bouchez O, Monteils V. Establish- 7. Mazmanian SK, Round JL, Kasper DL. A microbial symbiosis factor pre- ment of ruminal bacterial community in dairy calves from birth to weaning is vents intestinal inflammatory disease. Nature (2008) 453:620–5. doi:10.1038/ sequential. J Appl Microbiol (2014) 116:245–57. doi:10.1111/jam.12405 nature07008 29. De Barbieri I, Hegarty RS, Silveira C, Gulino LM, Oddy VH, Gilbert RA, et al. 8. Sjogren YM, Jenmalm MC, Bottcher MF, Bjorksten B, Sverremark-Ekstrom E. Programming rumen bacterial communities in newborn Merino lambs. Small Altered early infant gut microbiota in children developing allergy up to 5 years Rumin Res (2015) 129:48–59. doi:10.1016/j.smallrumres.2015.05.015 of age. Clin Exp Allergy (2009) 39:518–26. doi:10.1111/j.1365-2222.2008.03156 30. Jiao J, Huang J, Zhou C, Tan Z. Taxonomic identification of ruminal epithelial 9. Fouhy F, Guinane CM, Hussey S, Wall R, Ryan CA, Dempsey EM, et al. bacterial diversity during rumen development in goats. Appl Environ Microbiol High-throughput sequencing reveals the incomplete, short-term recovery of (2015) 81:3502–9. doi:10.1128/AEM.00203-15 infant gut microbiota following parenteral antibiotic treatment with ampicillin 31. Rey M, Enjalbert F, Monteils V. Establishment of ruminal enzymatic activities and gentamicin. Antimicrob Agents Chemother (2012) 56:5811–20. doi:10.1128/ and fermentation capacity in dairy calves from birth through weaning. J Dairy AAC.00789-12 Sci (2012) 95:1500–12. doi:10.3168/jds.2011-4902 10. Hansen CHF, Nielsen DS, Kverka M, Zakostelska Z, Klimesova K, Hudcovic T, 32. Abecia L, Martin-Garcia AI, Martinez-Fernandez G, Newbold CJ, Yanez-Ruiz et al. Patterns of early gut colonization shape future immune responses of the DR. Nutritional intervention in early life to manipulate rumen microbial col- host. PLoS One (2012) 7:e34043. doi:10.1371/journal.pone.0034043 onization and methane output by kid goats postweaning. J Anim Sci (2013) 11. Yeoman CJ, White BA. Gastrointestinal tract microbiota and probiotics in pro- 91:4832–40. doi:10.2527/jas.2012-6142 duction animals. Annu Rev Anim Biosci (2014) 2:469–86. doi:10.1146/annurev- 33. Abecia L, Waddams KE, Martinez-Fernandez G, Martin-Garcia AI, Ramos- animal-022513-114149 Morales E, Newbold CJ, et al. An antimethanogenic nutritional intervention 12. Cho SJ, Kim H, Yun HD, Cho KM, Shin EC, Lim WJ, et al. 16S rDNA analysis of in early life of ruminants modifies ruminal colonization by archaea. Archaea bacterial diversity in three fractions of cow rumen. J Microbiol Biotechnol (2006) (2014) 2014:841463. doi:10.1155/2014/841463 16:92–101. 34. Chanter N, Hall GA, Bland AP, Hayle AJ, Parsons KR. Dysentery in calves 13. Tajima K, Aminov RI, Nagamine T, Matsui H, Nakamura M, Benno Y. Diet- caused by an atypical strain of Escherichia coli (S102-9). Vet Microbiol (1984) dependent shifts in the bacterial population of the rumen revealed with real- 12:241–53. doi:10.1016/0378-1135(86)90053-2 time PCR. Appl Enivorn Microbiol (2001) 66:2766–74. doi:10.1128/AEM.67.6. 35. Hall GA, Reynold DJ, Chanter N, Morgan JH, Parsons KR, Debney 2766-2774.2001 TA, et al. Dysentery caused by Escherichia coli (S102-9) in calves: nat- 14. Kim M, Morrison M, Yu Z. Status of the phylogenetic diversity census of ural and experimental disease. Vet Pathol (1985) 22:156–63. doi:10.1177/ ruminal microbiomes. FEMS Microbiol Ecol (2011) 76:49–63. doi:10.1111/j. 030098588502200210 1574-6941.2010.01029 36. Moxley RA, Francis DH. Natural and experimental infection with an attach- 15. Pounden WD, Hibbs JW. The influence of ration and rumen inoculation on the ing and effacing strain of Escherichia coli in calves. Infect Immunol (1986) establishment of certain microorganisms in the rumens of young calves. J Dairy 53:336–49. Sci (1948) 31:1041–50. doi:10.3168/jds.S0022-0302(48)92296-6 37. Janke BH, Francis DH, Collins JE, Libal MC, Zeman DH, Johnson DD. Attach- 16. Pounden WD, Hibbs JW. The influence of pasture and rumen inoculation on ing and effacing Escherichia coli infections in calves, pigs, lambs, and dogs. J Vet the establishment of certain microorganisms in the rumen of young dairy calves. Diagn Invest (1989) 1:6–11. doi:10.1177/104063878900100104 J Dairy Sci (1949) 32:1025–32. doi:10.3168/jds.S0022-0302(49)92157-8 38. Zhao T, Doyle MP, Harmon BG, Brown CA, Mueller POE, Parks AH. Reduction 17. Fonty G, Gouet P, Jounay JP, Senaud J. Establishment of the microflora and of carriage of enterohemorrhagic Escherichia coli O157:H7 in cattle by inocula- anaerobic fungi in the rumen of lambs. Microbiology (1987) 133:1835–43. doi: tion with probiotic bacteria. J Clin Microbiol (1998) 36:641–7. 10.1099/00221287-133-7-1835 39. Abe F, Ishibashi N, Shimamura S. Effect of administration of bifidobacteria and 18. Fonty G, Senaud J, Jouany JP, Gouet P. Establishment of ciliate protozoa in the lactic acid bacteria to newborn calves and piglets. J Dairy Sci (1995) 73:2838–46. rumen of conventional and conventionalized lambs: influence of diet and man- doi:10.3168/jds.S0022-0302(95)76914-4 agement conditions. Can J Microbiol (1988) 34:235–41. doi:10.1139/m88-044 40. Al-Saiady MY. Effect of probiotic bacteria on immunoglobulin G concentration 19. Fonty G, Gouet P, Nebout JM. Development of the cellulolytic microflora in and other blood components of newborn calves. J Anim Vet Adv (2010) 9:604–9. the rumen of lambs transferred into sterile isolators a few days after birth. Can doi:10.3923/java.2010.604.609 J Microbiol (1989) 35:416–22. doi:10.1139/m89-064 41. Marquez CJ. Calf Intestinal Health: Assessment and Dietary Interventions for its 20. Rieu F, Fonty G, Gaillard B, Gouet P. Electron microscopy study of the bacteria Improvement. PhD thesis, University of Illinois at Urbana-Champaign, Cham- adherent to the rumen wall in young conventional lambs. Can J Microbiol (1990) paign, IL (2014). 36:140–4. doi:10.1139/m90-025 42. Uyeno Y, Shigemori S, Shimosato T. Effect of probiotics/prebiotics on cat- 21. Malmuthuge N, Griebel PJ, Guan LL. Taxonomic identification of commensal tle health and productivity. Microbes Environ (2015) 30:126–32. doi:10.1264/ bacteria associated with the mucosa and digesta throughout the gastrointestinal jsme2.ME14176 tracts of pre-weaned calves. Appl Environ Microbiol (2014) 80:2012–28. doi:10. 43. Smith HW. The development of the flora of the alimentary tract in young 1128/AEM.03864-13 animals. J Pathol Bacteriol (1965) 90:495–513. doi:10.1002/path.1700900218 Frontiers in Veterinary Science | www.frontiersin.org 21 September 2015 | Volume 2 | Article 36 Malmuthuge et al. Microbiome and bovine gut development 44. Rada V, Vlkov E, Nevoral J, Trojanov I. Comparison of bacterial flora and 61. Reynolds JD, Morris B. The effect of antigen on the development of Peyer’s enzymatic activity in faeces of infants and calves. FEMS Microbiol Lett (2006) patches in sheep. Eur J Immunol (1984) 14:1–6. doi:10.1002/eji.1830140102 258:25–8. doi:10.1111/j.1574-6968.2006.00207 62. Rakoff-Nahoum S, Paglino J, Eslami-Varzaneh F, Edberg S, Medzhitov R. 45. Vlkova E, Nevoral J, Rada V. Distribution of bifidobacteria in the gastrointesti- Recognition of commensal microflora by toll-like receptors is required for nal tract of calves. Folia Microbiol (2006) 51:325–8. doi:10.1007/BF02931825 intestinal homeostasis. Cell (2004) 118:229–41. doi:10.1016/j.cell.2004.07.002 46. Uyeno Y, Sekiguchi Y, Kamagata Y. rRNA-based analysis to monitor succession 63. Teran R, Mitre E, Vaca M, Erazo S, Oviedo G, Hubner MP, et al. Immune system of fecal bacterial communities of Holstein calves. Lett Appl Microbiol (2010) development during early childhood in tropical Latin America: evidence for the 51:570–7. doi:10.1111/j.1472-765X.2010.02937 age-dependent down regulation of the innate immune response. Clin Immunol 47. Oikonomou G, Teixeira AG, Foditsch C, Bichalho ML, Machado VS, Bicalho (2011) 138:299–310. doi:10.1016/j.clim.2010.12.011 RC. Fecal microbial diversity in pre-weaned dairy calves as described by pyrose- 64. Fries P, Popwych YI, Guan LL, Griebel PJ. Age-related changes in the distribu- quencing of metagenomic 16S rDNA. Associations of Faecalibacterium species tion and frequency of myeloid and T cell populations in the small intestine of with health and growth. PLOS One (2013) 8:e63157. doi:10.1371/journal.pone. calves. Cell Immunol (2011) 271:428–37. doi:10.1016/j.cellimm.2011.08.012 0063157 65. Malmuthuge N, Fries P, Griebel PJ, Guan LL. Regional and age dependent 48. Collado MC, Sanz Y. Quantification of mucosa-adhered microbiota of lambs changes in gene expression of toll-like receptors and key antimicrobial defence and calves by the use of culture methods and fluorescent in situ hybridization molecules throughout the gastrointestinal tract of dairy calves. Vet Immunol coupled with flow cytometry techniques. Vet Microbiol (2007) 121:299–306. Immunopathol (2012) 146:18–26. doi:10.1016/j.vetimm.2012.01.010 doi:10.1016/j.vetmic.2006.12.006 66. Liang G, Bao H, McFadden T, Stothard P, Griebel PJ, Guan LL. Potential 49. Malmuthuge N, Li M, Chen Y, Fries P, Griebel PJ, Baurhoo B, et al. Distinct regulatory role of microRNAs in the development of bovine gastrointestinal commensal bacteria associated with ingesta and mucosal epithelium in the tract during early life. PLoS One (2014) 9:e92592. doi:10.1371/journal.pone. gastrointestinal tracts of calves and chickens. FEMS Microbiol Ecol (2012) 0092592 79:337–47. doi:10.1111/j.1574-6941.2011.01220 67. Uetake K. Newborn calf welfare: a review focusing on mortality rates. Anim Sci 50. Romano-Keeler J, Moore DJ, Wang C, Brucker RM, Fonnesbeck C, Slaughter J (2013) 84:101–5. doi:10.1111/asj.12019 JC, et al. Early life establishment of site-specific microbial communities in the 68. Sokol H, Seksik P, Furet JP, Fermisse O, Nion-Larmurier I, Beaugerie L, et al. gut. Gut Microbes (2014) 5:192–201. doi:10.4161/gmic.28442 Low counts of Faecalibacterium prausnitzii in colitis microbiota. Inflamm Bowel 51. Malmuthuge N, Li M, Goonewardene LA, Guan LL. Effect of calf starter feeding Dis (2009) 15:1183–9. doi:10.1002/ibd.20903 on gut microbial diversity and expression of genes involved in host immune 69. Morrill KM, Conrad E, Lago A, Campbell J, Quigley J, Tyler H. Nationwide responses and tight junctions in dairy calves during weaning transition. J Dairy evaluation of quality and composition of colostrum on dairy farms in the United Sci (2013) 96:3189–200. doi:10.3168/jds.2012-6200 States. J Dairy Sci (2012) 95:3997–4005. doi:10.3168/jds.2011-5174 52. Malmuthuge N, Chen Y, Liang G, Goonewardane LA, Guan LL. Heat-treated 70. Vasseur E, Borderas F, Cue RI, Lefebvre D, Pellerin D, Rushen J, et al. A survey colostrum feeding promotes beneficial bacteria colonization in the small intes- of dairy calf management practices in Canada that affect animal welfare. J Dairy tine of neonatal calves. J Dairy Sci (2015) (in press). doi:10.3168/jds.2015-9607 Sci (2010) 93:1307–15. doi:10.3168/jds.2009-2429 53. Abecia L, Ramos-Morales E, Martinez-Fernandez G, Arco A, Martin-Garcia 71. Godden SM, Smolenski DJ, Donahue M, Oakes JM, Bey R, Wells S, et al. Heat- AI, Newbold CJ, et al. Feeding management in early life influences microbial treated colostrum and reduced morbidity in preweaned dairy calves: results of colonization and fermentation in the rumen of newborn goat kids. Anim Prod a randomized trial and examination of mechanisms of effectiveness. J Dairy Sci Sci (2014) 54:1449–54. doi:10.1071/AN14337 (2012) 95:4029–40. doi:10.3168/jds.2011-5275 54. Sommer F, Backhed F. The gut microbiota – masters of host development and 72. Fukuda S, Toh H, Hase K, Oshima K, Nakanishi Y, Yoshimura K, et al. Bifi- physiology. Nat Rev Micorbiol (2013) 11:227–38. doi:10.1038/nrmicro2974 dobacteria can protect from enteropathogenic infection through production of 55. Petersson J, Schreiber O, Hansson GC, Gendler SJ, Velcich A, Lundberg JO, acetate. Nature (2011) 469:543–7. doi:10.1038/nature09646 et al. Importance and regulation of the colonic mucus barrier in a mouse 73. Krehbiel CR, Rust SR, Zhang G, Gilliland SE. Bacterial direct-fed microbials in model of colitis. Am J Physiol Gastrointest Liver Physiol (2011) 300:G327–33. ruminant diets: performance response and mode of action. J Anim Sci (2003) doi:10.1152/ajpgi.00422.2010 81:E120–32. 56. Nowacki MR. Cell proliferation in colonic crypts of germ-free and con- 74. Charavaryamath C, Gonzalez-Cano P, Fries P, Gomis S, Doig K, Scruten E, et al. ventional mice – preliminary report. Folia Histochem Cytobiol (1993) 31: Host responses to persistent Mycobacterium avium subspecies paratuberculosis 77–81. infection in surgically isolated bovine ileal segments. Clin Vaccine Immunol 57. Chung H, Pamp SJ, Hill JA, Surana NK, Edelman SM, Troy EB, et al. Gut (2013) 20:156–65. doi:10.1128/CVI.00496-12 immune maturation depends on colonization with a host-specific microbiota. Cell (2012) 149:1578–93. doi:10.1016/j.cell.2012.04.037 Conflict of Interest Statement: The authors declare that the research was con- 58. Griebel PJ, Hein WR. Expanding the role of Peyer’s patches in B-cell ontogeny. ducted in the absence of any commercial or financial relationships that could be Immunol Today (1996) 17:30–8. doi:10.1016/0167-5699(96)80566-4 construed as a potential conflict of interest. 59. Yasuda M, Fujino M, Nasu T, Murakami T. Histological studies on the ontogeny of bovine gut-associated lymphoid tissue: appearance of T cells and develop- Copyright © 2015 Malmuthuge, Griebel and Guan. This is an open-access article ment of IgG+ and IgA+ cells in lymphoid follicles. Dev Comp Immunol (2004) distributed under the terms of the Creative Commons Attribution License (CC BY). 28:357–69. doi:10.1016/j.dci.2003.09.013 The use, distribution or reproduction in other forums is permitted, provided the 60. Gerdts V, Babiuk LA, van Drunen Littel-van den Hurk S, Griebel PJ. Fetal original author(s) or licensor are credited and that the original publication in this immunization by a DNA vaccine delivered orally into the amniotic fluid. Nat journal is cited, in accordance with accepted academic practice. No use, distribution Med (2000) 6:929–32. doi:10.1038/78699 or reproduction is permitted which does not comply with these terms. Frontiers in Veterinary Science | www.frontiersin.org 22 September 2015 | Volume 2 | Article 36 Original Research published: 20 January 2016 doi: 10.3389/fvets.2016.00002 Development of the Chick Microbiome: How Early Exposure Influences Future Microbial Diversity Anne L. Ballou1 , Rizwana A. Ali1 , Mary A. Mendoza1 , J. C. Ellis2 , Hosni M. Hassan1 , W. J. Croom1 and Matthew D. Koci1* 1 Prestage Department of Poultry Science, North Carolina State University, Raleigh, NC, USA, 2 In Silico LLC, Fuquay-Varina, NC, USA The concept of improving animal health through improved gut health has existed in food animal production for decades; however, only recently have we had the tools to identify microbes in the intestine associated with improved performance. Currently, little is known about how the avian microbiome develops or the factors that affect its composition. To begin to address this knowledge gap, the present study assessed the development of the cecal microbiome in chicks from hatch to 28 days of age with and without a live Salmonella vaccine and/or probiotic supplement; both are products intended to promote gut health. The microbiome of growing chicks develops rapidly from days 1–3, and the Edited by: microbiome is primarily Enterobacteriaceae, but Firmicutes increase in abundance and Michael Kogut, taxonomic diversity starting around day 7. As the microbiome continues to develop, the USDA-ARS, USA influence of the treatments becomes stronger. Predicted metagenomic content suggests Reviewed by: Carl James Yeoman, that, functionally, treatment may stimulate more differences at day 14, despite the strong Montana State University, USA taxonomic differences at day 28. These results demonstrate that these live microbial Brian B. Oakley, treatments do impact the development of the bacterial taxa found in the growing chicks; Western University of Health Sciences, USA however, additional experiments are needed to understand the biochemical and func- *Correspondence: tional consequences of these alterations. Matthew D. Koci [email protected] Keywords: chicken, microbiome development, Salmonella, probiotic, gut development Specialty section: This article was submitted to Veterinary Infectious Diseases, INTRODUCTION a section of the journal Frontiers in Veterinary Science Increasing evidence in multiple species demonstrate the impact gut microbes have on intestinal Received: 31 July 2015 function, digestion, host metabolism, and immune function (1, 2). While the food animal industry Accepted: 05 January 2016 has employed various methods to control and augment the bacteria in the gut for decades, this Published: 20 January 2016 has been done with little understanding of the complexity of the microbial populations and their Citation: association with animal health. The advent of microbiome analysis will allow for better use of these Ballou AL, Ali RA, Mendoza MA, Ellis JC, Hassan HM, Croom WJ and Koci MD (2016) Development of the Abbreviations: ANOSIM, analysis of similarity; DC, diluent-control; DP, diluent-probiotic; FDR, false discovery rate; KEGG, Chick Microbiome: How Early Kyoto Encyclopedia of Genes and Genomes; MANOVA, multivariate analysis of variance; OTU, operational taxonomic Exposure Influences Future Microbial unit; PERMANOVA, Permutational MANOVA; PICRUSt, phylogenetic investigation of communities by reconstruction of Diversity. unobserved states; PCoA, principal coordinate analysis; QIIME, quantitative insights into microbial ecology; ST, Salmonella Front. Vet. Sci. 3:2. Typhimurium; SIMPER, similarity percentage analysis; STAMP, statistical analysis of metagenomics profiles; VC, vaccine- doi: 10.3389/fvets.2016.00002 control; VP, vaccine-probiotic. Frontiers in Veterinary Science | www.frontiersin.org 23 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome products and the rational design of new therapies to promote MATERIALS AND METHODS animal health and performance. An estimated $585 million/ year is spent globally on interventions to manage disease Animals and Treatments in food animals (3); many of these diseases are intestinal Two hundred one-day-old female commercial white leghorn lay- in nature (4), and the indirect costs of these intestinal dis- ing type chickens (W-36, Hy-line International) were assigned to eases are far greater. The application of modern nucleotide one of four treatments (50 chicks/treatment) in a 2 × 2 factorial sequencing and associated bioinformatics techniques to the design. The four groups were designated as follows: Diluent- avian gastrointestinal microbiome will lead to breakthroughs Control (DC); Diluent-Probiotic (DP); Vaccine-Control (VC); in our understanding of digestive processes, host metabolic and Vaccine-Probiotic (VP). Animals received either a one-time regulation, immune function, and intestinal dysfunction and dose of a live, attenuated ST spray vaccine (Salmune®, Ceva pathology. Collectively, increased understanding of the host– Biomune, Lenexa, KS; Vaccine group) or a sham vaccination microbiome relationship, and the development of techniques consisting of the vaccine diluent, water (Diluent group). The vac- to improve these interactions, could reduce the prevalence of cine and diluent spray were administered as recommended by the food-borne pathogens. In order to effectively apply modern manufacturer. These treatment groups were further divided into microbial ecology research techniques and elucidate the man- two dietary groups; one group (Control) was fed a standard corn– ner in which the avian intestinal microbiome interacts with soybean starter diet (Table S1 in Supplementary Material) and the the host genome, it is imperative to develop a comprehensive probiotic group was fed an identical starter diet supplemented understanding of how the avian microbiome develops under with 0.1% (w/w) of the probiotic PrimaLac® (L. acidophilus, L. different physiological states and management practices. casei, E. faecium, B. bifidum; Star Labs Inc., Clarksdale, MO, USA; There is a dearth of information available on the devel- Probiotic group). Probiotic pre-mix was added to the probiotic opment and definition of a normal avian gut microbiome. groups’ feed prior to the experiment and animals in all groups Recent investigations have begun to identify species com- were fed ad libitum for 4 weeks. monly seen in adult chickens, but little is known about the Animals in all groups were housed in 934-1-WP isolators (L. intermediate and developing community (5–7). Furthermore, H. Leathers Inc., Athens GA) climate-controlled HEPA-filtered there is a paucity of information of the effects of treatments isolation units. The animals were maintained and euthanized that target the gut environment on the development of the under an approved protocol from the North Carolina State intestinal microbiome of chickens. This impairs our ability to University Institutional Animal Care and Use Committee (OLAW understand how these gut-targeted treatments interact with #A3331-01). each other and the host, and how they might affect gut activ- ity and health. A better understanding of these interactions Sample Collection will allow for the rational use of bacterial groups to promote Six chickens from each treatment group were euthanized (CO2 specific host responses. followed by cervical dislocation) on days 0, 1, 3, 7, 14, and 28 The goal of this study was to understand the ontogeny of and the contents of one cecal lobe collected and maintained on the chicken intestinal microbiome, and how commonly used ice. At early timepoints, some chicks yielded minimal or no cecal live bacterial treatments influence this dynamic microbial digesta; these are noted in Table S2 in Supplementary Material. community. Specifically, we included two live bacterial The cecal samples were weighed and diluted with 600 μl of 30% products currently used in the industry that are intended glycerol in PBS for storage at −80°C. to improve animal health through manipulation of the host microbiota. We used a live attenuated Salmonella enterica, DNA Isolation and 16S Sequencing serovar Typhimurium vaccine (Salmune®, CEVA Biomune), DNA was isolated from each cecal sample using the MO BIO and a probiotic feed supplement comprised of Lactobacillus Power Soil kit (MO BIO, Carlsbad, CA, USA) with the following acidophilus, Lactobacillus casei, Enterococcus faecium, and modifications: a 10-min, 65°C incubation step was added and Bifidobacterium bifidum(PrimaLac®, Star Labs). We hypoth- samples were then homogenized for 45 s at 5100 RPM using esized that the species richness of the microbiome would garnet bead-containing tubes and a Precellys 24 homogenizer increase rapidly, and the addition of live bacterial treatments (Precellys, Montigny-le-Bretonneux, France). would alter the development of microbial diversity and the DNA recovered from the extraction process was quanti- composition of the microbiome. The results from this study fied using a NanoDrop 2000 spectrophotometer (NanoDrop, demonstrated exposing developing chickens to individual Wilmington, DE, USA) and 10 ng from each sample were or combined bacterial regimens leads to treatment-specific aliquoted into 96-well plates in a random order. Some animals microbial populations. These populations continue to diverge contained only small amounts of cecal digesta, particularly at with age, even in animals receiving only a one-time dose of days 0–3, resulting in very small amounts of DNA for some the Salmonella Typhimurium (ST) vaccine at day of hatch. samples. DNA from these samples was included in the sequenc- Predicted metagenomic content in these populations sug- ing process, despite the possibility of poor quality sequencing gest changes in potential microbial metabolic activity and (Table S2 in Supplementary Material). MiSeq library prepara- microbe-derived signaling molecules; however, these changes tion and 151 × 151 paired-end sequencing (Illumina, San were less numerous than the taxonomic changes seen in the Diego, CA, USA) were performed by the Argonne National same populations. Laboratory Institute for Genomics and Systems Biology Next Frontiers in Veterinary Science | www.frontiersin.org 24 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome Generation Sequencing Core using a protocol and primers rec- Metagenomic inferences from the 16S amplicon data were ommended and previously described by the Earth Microbiome made using the QIIME suite of tools (14, 15, 17, 18), PICRUSt project and others. Primers used spanned the V4 region of (20), and KEGG (21); statistics and visualization of functional the 16S rRNA gene (515F: GTGYCAGCMGCCGCGGTAA, data were depicted using STAMP (22). Closed-reference 806R: GGACTACHVGGGTWTCTAAT) (8). This primer set OTU-picking protocols were used to identify 16S sequences is commonly used to evaluate the microbiome community belonging to annotated genomes. Briefly, sequences were across a variety of fields, and is well validated in several grouped into OTUs based on 97% sequence identity using models, including the chicken (8–11). Studies estimating uclust and the Greengenes reference database. Representative microbial composition using V4 sequence information report sequences from each OTU were picked and assigned taxonomy diversity measurements comparable to those obtained with using the uclust consensus taxonomy assigner. PICRUSt and full-length 16S sequences (12). KEGG were used to generate a list of functional genes pre- dicted to be present in the sample and to organize these genes Sequence Data Analysis into gene pathways. Using STAMP, heatmaps were generated The unpaired raw sequencing reads were paired and filtered using displaying differences in gene-group abundance at each time EA-Utils (13). Paired reads were processed using the QIIME suite point. In order to minimize the number of treatment-based of tools (v 1.8.0) (14); barcode matching and quality filtering were differences that may not be biologically relevant, analysis was conducted prior to picking operational taxonomic units (OTUs). limited to those differences with an effect size greater than 0.7 The 16S sequencing process did not yield equal sequence coverage as calculated by STAMP (eta-squared method) (22). Storey’s for all samples, and some samples had very low sequence cover- FDR correction was applied to all comparisons between treat- age. Samples with low sequence coverage or consistently poor ments (23). Nearest neighbor hierarchical clustering was used quality were excluded from analysis. Additionally, some ceca to group each sample according to abundance of gene groups from early time points contained little to no recoverable digesta. in question. Consequently, a small number of samples from different time points were removed at this stage (Table S2 in Supplementary Material). OTUs were picked using an open-reference proto- RESULTS col. Briefly, sequences were grouped into OTUs based on 97% sequence identity using uclust and the Greengenes reference Microbiome Composition and Complexity database (15, 16). OTUs that failed to match to the database were Change Rapidly with Age reclustered, resampled, and re-compared to the database; in this 16S rRNA sequence analysis of the microbiome from the ceca of way, new reference sequences are compared to the database in untreated animals (DC) demonstrated a microbiome with low order to minimize the number of excluded sequences. Finally, diversity in days 0 and 1, dominated by Enterobacteriaceae and OTUs that failed to align to any sequences in the reference to a lesser extent Enterococcus (Figure 1). The number of OTUs database are de novo clustered. Representative sequences from detected in the microbiome increased significantly (P < 0.05) each OTU were picked and assigned taxonomy using the uclust by day 3 (data not shown). This increase in bacterial richness consensus taxonomy assigner. During this process, sequences starts with Ruminococcaceae groups during the first week of life with high identity (>97%) were grouped into the same OTU, and and continues with other Firmicutes. By day 14, and extending are reported at the lowest level of taxonomic identification com- through day 28, Ruminococcus and other Firmicutes outnumber mon to all sequences (17, 18). Sequence coverage was normalized Enterobacteriaceae (Figure 1). across samples in each analysis. Taxonomic assignments, and alpha and beta diversity metrics were generated using QIIME and Primer-E (v6.1.16; Primer-E LTD, Ivybridge, UK). Principal Age More Influential in Microbiome coordinate analysis (PCoA) plots used in this study were gener- Development than Treatment ated in Primer-E using the Bray–Curtis distance metric (19). Principal coordinate analysis of samples across all time points Permutational multivariate analysis of variance and treatment groups reveals that the effect of animal age (PERMANOVA) was conducted using the PERMANOVA+ add- on community composition was larger than that of bacterial on to Primer-E. Main and pair-wise tests were conducted using treatment (Figure 2A). The ANOSIM-generated global test up to 1000 permutations of residuals under a reduced model. statistics for time (R = 0.67) and the treatments (Vaccine Similarity percentage analysis (SIMPER) of taxonomic groups R = 0.361, Probiotic R = 0.317) demonstrate the relative between treatment groups and times was made in Primer-E using impact of each on the community. At time points 0–7, the Bray–Curtis distances. Analysis of similarity (ANOSIM) tests samples show large within time point variability. At day 28, were conducted using Primer-E. Tests were conducted using up within time point variability is decreased and samples are to 1000 permutations and the Spearman rank correlation method. tightly clustered in the PCoA plot (Figure 2A). Community A global test statistic (R) was generated for each treatment; the analysis of cecal samples across time points and treatment rank similarities between and within treatments were calculated groups show that Gram-negative bacteria (Proteobacteria) and compared. The global R statistic is a measure of the strength dominate at early time points, while Gram-positive Firmicutes, of a treatment group’s association with microbiome composition, especially Clostridia taxa, become more prominent with age with 1 being the strongest association and 0 being no association. (Figure 2B). Frontiers in Veterinary Science | www.frontiersin.org 25 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome Figure 1 | As the cecal microbiome develops, the dominant taxa shift from Gram-negative to Gram-positive bacteria. A heatmap of taxonomic groups present in untreated (DC) samples over time was generated with Qiime. The composition of the microbiome in DC animals was evaluated to identify trends in the development of the normal microbiome over time. There is a consistent decrease in the proportion of Enterobacteriaceae and Enterococcus over time, and an increase in levels of Clostridiales groups like Ruminococcus and Oscillospira. Sequence coverage was normalized to 16,260 reads/sample. Treatments Alter Microbial Composition most abundant order, Clostridiales, including Lachnospiraceae and Rate of Development and Ruminococcaceae genera (Tables 1 and 2). MANOVA was Analyses of microbial populations were conducted within each used to identify differentially abundant taxa between treatment time point (days 1, 7, 14, and 28) to assess the impact of treatment groups, with an FDR correction made to account for multiple on composition and richness of the microbiome independent of comparisons. At day 14, DC animals harbored a significantly age. No differences in microbial composition were detected at higher proportion of Enterobacteriaceae (Table 1) with 16% day 1, but significant differences in cecal microbiome composi- Enterobacteriaceae as compared to 3–9% in the other treat- tion were observed among all four treatment groups by day 7 ments. Lactobacillus was significantly increased in the DP group (Figure 3A). A PERMANOVA showed that all four treatment relative to DC. At day 14, 83% of significantly different taxa were groups are distinct in composition at days 7, 14, and 28 (P < 0.05). Firmicutes, and 63% were Clostridia. A comparison of taxonomic richness (alpha diversity) among Analysis of the taxonomic groups represented in each treat- treatment groups at days 1, 7, 14, and 28 was made using rarefac- ment at day 28 indicate that most significant changes occur in tion plots. The treatment groups show similar levels of unique the Firmicutes phylum, including differences in the abundance taxa at day 1; however, at days 7 and 14, probiotic groups tend of Ruminococcaceae, Lachnospiraceae, and Peptostreptococcaceae to have fewer unique taxa (P < 0.1 at day 7, P < 0.05 at day 14). (Table 2). Lactobacillus is also increased in the DP group relative Interestingly, there was no significant difference in alpha diversity to DC. Eighty-one percent of all significantly different taxa at day at day 28 (Figure 3B). 28 were in the Order Clostridiales. Treatment with Live Bacteria Affects Treatment-Induced Changes in Abundance of Taxa not Associated With Microbiome Diversity Lead to Predicted Treatment Changes in Abundance of Functional Gene Similarity percentage analysis conducted between treatment Families groups at days 14 and 28 indicates that the differences between Estimates were made of the functional changes that may treatment groups can largely be attributed to changes in the occur in the cecal microbiome following treatment using Frontiers in Veterinary Science | www.frontiersin.org 26 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome Figure 2 | Age is the dominant factor in the composition of the microbiome. (A) Principal coordinate analysis of samples was conducted using Primer-E and samples were labeled based on age. Samples are clustered on two axes based on a multi-dimensional analysis of their sequence diversity and abundance. As the animals age, their microbiome increases in complexity but decreases in variability between samples, even between treatment groups. The effect of age was stronger than the effect of vaccine or probiotic. Differences between all time points were significant at permutational P-value <0.05, with the exception of day 0 vs. days 1 and 3. Coordinate loading for each principal coordinate shows the primary taxonomic groups contributing to each axis. Each data point represents a sample in the appropriate time point, and samples from all treatment groups are included in the analysis. (B) The phylum and class of sequences with an average relative abundance of 1% or greater are displayed by time point and treatment. All treatment groups started with high levels of Gammaproteobacteria that shifted with age into a Firmicutes-dominated community with large numbers of Clostridia. Taxonomy assignments were generated with QIIME, and PCoA plots were generated with Primer-E. Sequence coverage was normalized to 16,260 reads/sample. closed-reference OTU-picking and PICRUSt. Gene groups VC groups were minor, but the DP group displayed the lowest targeted for statistical analysis had an FDR-corrected P < 0.01, expected abundance of two-component system and bacterial and an effect size of 0.7 or higher. At day 14, samples cluster motility genes. primarily by probiotic treatment, and the VP group is most Fewer gene groups met the inclusion criteria at day 28, and the distinct from other treatments. The combination of ST and total relative abundance of included gene groups was lower than probiotic treatments increases the expected proportion of that at day 14. At day 28, DP and VP treatment groups display genes related to environment-sensing; two-component sys- higher predicted levels of genes related to one carbon metabolism, tems, bacterial motility, chemotaxis, and flagellar component terpenoid synthesis, and translation proteins (Figure 4B). DC assembly genes were predicted to increase. DC, DP, and VC and DP groups had higher proportions of fatty acid metabolism, groups have relatively higher abundance of genes related to drug metabolism, and signal transduction gene pathways. amino acid metabolism, DNA repair and replication, and Relative abundance tables of taxa and predicted gene groups translation (Figure 4A). The differences between DC, DP, and were used to generate area charts of between-treatment changes Frontiers in Veterinary Science | www.frontiersin.org 27 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome Figure 3 | Principal coordinate analysis and rarefaction analyses demonstrate the impact of the treatments over time. (A) Principal coordinate analysis generated with Primer-E demonstrates the effect of treatments at 1, 7, 14, and 28 days of age. There are no significant treatment differences at day 1. By day 7, treatment groups are statistically different based on PERMANOVA tests. Treatment groups cluster visually at days 14 and 28. All treatment groups at days 7, 14, and 28 were different at permutational P < 0.05. (B) Rarefaction of observed species (unique OTUs) at individual time points was conducted using QIIME, and demonstrate the rapid development of taxonomic diversity. Treatment groups show similar diversity at Day 1. At day 7, DP and VP tend to have lower diversity than VC (P = 0.078 and 0.054, respectively). At day 14, DP and VP diversity is significantly lower than DC and VC diversity (P < 0.05). By day 28, community diversity is similar between treatments. Sequence coverage was normalized for each time point individually: day 1 (16,577 reads/sample), day 7 (16,668 reads/sample), day 14 (20,263 reads/sample), and day 28 (20,263 reads/sample). Frontiers in Veterinary Science | www.frontiersin.org 28 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome Table 1 | Similarity percentage analysis (SIMPER) of treatment groups at day 14a. Phylum Class Order Family Genus Average % Contribution to abundance (%) dissimilarityb DC DP Firmicutes Bacilli Lactobacillales Lactobacillaceae Lactobacillus 1 16* 19.4 Proteobacteria Gammaproteobacteria Enterobacteriales Enterobacteriaceaec 16 3* 15.65 Firmicutes Clostridia Clostridiales Lachnospiraceae Ruminococcus 25 26 15.27 Firmicutes Clostridia Clostridiales Ruminococcaceae 19 14* 9.01 Firmicutes Clostridia Clostridiales Ruminococcaceae Oscillospira 11 15 8.58 DC VC Firmicutes Clostridia Clostridiales Lachnospiraceae 8 16* 15.4 Firmicutes Clostridia Clostridiales 4 12* 14.57 Firmicutes Clostridia Clostridiales Ruminococcaceae 19 13* 13.61 Firmicutes Clostridia Clostridiales Lachnospiraceae Ruminococcus 25 24 13.28 Proteobacteria Gammaproteobacteria Enterobacteriales Enterobacteriaceae 16 9* 13.12 DC VP Firmicutes Clostridia Clostridiales Lachnospiraceae 8 39* 25.58 Firmicutes Clostridia Clostridiales Lachnospiraceae Ruminococcus 25 2* 18.69 Firmicutes Clostridia Clostridiales Ruminococcaceae 19 3* 13.46 Proteobacteria Gammaproteobacteria Enterobacteriales Enterobacteriaceae 16 5* 9.07 Firmicutes Clostridia Clostridiales 4 14* 8.95 a Top 5 taxa shown for each comparison. b Percent contribution to total dissimilarity between treatment groups under comparison. c If a sequence matches more than one possible taxon, classification stops at the next highest level. *Indicates significance at P ≤ 0.05. Table 2 | Similarity percentage analysis (SIMPER) of treatment groups at day 28a. Phylum Class Order Family Genus Average abundance (%) % Contribution to dissimilarityb DC DP Firmicutes Clostridia Clostridiales Lachnospiraceae Ruminococcusc 12 19 16.65 Firmicutes Clostridia Clostridiales Ruminococcaceae 11 18* 12.94 Firmicutes Clostridia Clostridiales Other Otherd 11 5* 9.57 Firmicutes Clostridia Clostridiales Ruminococcaceae Oscillospira 12 8* 9.22 Firmicutes Clostridia Erysipelotrichales Erysipelotrichaceae 2 5 7.73 DC VC Firmicutes Clostridia Clostridiales 12 21* 15.41 Firmicutes Clostridia Clostridiales Lachnospiraceae 15 10* 13.49 Firmicutes Clostridia Clostridiales Other Other 11 4* 12.26 Firmicutes Clostridia Clostridiales Ruminococcaceae Ruminococcus 5 9 7.53 Firmicutes Clostridia Clostridiales Lachnospiraceae Ruminococcus 12 12 7.45 DC VP Firmicutes Clostridia Clostridiales 12 36* 32.27 Firmicutes Clostridia Clostridiales Lachnospiraceae 15 5* 14.03 Firmicutes Clostridia Clostridiales Other Other 11 1* 13.05 Firmicutes Clostridia Clostridiales Ruminococcaceae 11 16* 6.85 Firmicutes Clostridia Clostridiales Lachnospiraceae Ruminococcus 12 11 5.11 a Top 5 taxa shown for each comparison. b Percent contribution to total dissimilarity between treatment groups under comparison. c If a sequence matches more than one possible taxon, classification stops at the next highest level. d “Other” indicates the sequence in question has not been assigned to a taxonomic group at that level. *Indicates significance at P ≤ 0.05. in taxa and gene groups. Vaccine and Probiotic groups differ DISCUSSION from the DC group taxonomically at both days 14 and 28. Gene-group abundance shows less treatment-specific variability Little is known about the development of the microbiome in (Figure 5). young birds, and how it is affected by different stimuli (7). The Frontiers in Veterinary Science | www.frontiersin.org 29 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome Figure 4 | At both days 14 and 28, the VP group shows the greatest divergence in predicted metagenomic content. PICRUSt was used to generate a list of genes inferred to be present in the samples, their relative abundance, and the gene pathways with which they are associated. A heatmap was generated with STAMP. Samples were clustered using a nearest neighbor metric, and pathways were colored based on their percent abundance relative to all measured genes. All listed gene groups are significantly different between treatment groups with an effect size >0.70 and FDR-corrected P < 0.01. The combination of vaccine and probiotic treatments stimulates changes in several gene groups and pathways at day 14 (A), namely increases in chemotaxis, two-component system, flagellar assembly, and bacterial motility. Decreases in the VP group include metabolic processes, such as amino acid metabolism, DNA replication, and protein translation. (B) There are fewer significantly different pathways at day 28 and changes are largely related to cell metabolism. Frontiers in Veterinary Science | www.frontiersin.org 30 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome Figure 5 | Comparison of taxonomic and gene-group abundance trends at days 14 and 28. Relative abundance of taxonomic groups and predicted abundance of functional gene groups demonstrate the stability of gene-group abundances relative to changes in taxonomic groups. Relative abundance tables for taxa and gene group were assembled and used to generate area charts of all samples at days 14 and 28. The relative abundance of every identified taxonomic or functional gene group is shown for each sample; (A) predicted gene groups at day 14, (B) taxonomic groups at day 14, (C) predicted gene groups at day 28, (D) taxonomic groups at day 28. At day 14, there are clear taxonomic differences between treatments (A), and smaller changes in the abundance of a few gene groups (B). At day 28, taxonomic changes (D) are accompanied by few visible changes in gene-group abundance (C). goal of this study was to characterize the healthy developing of Gram-positive bacteria, mainly within the Clostridiales group, microbiome in chickens and understand how commonly used resulting in a correspondingly smaller proportion of Gram- bacterial treatments intended to improve or maintain health negative bacteria (Figure 1). The proportion of Gram-negative would affect this process. This is important in the food animal bacteria in the cecum at day 28 is <6%, and it is almost entirely industry as there are numerous feed additives intended to improve Enterobacteriaceae. animal health, either directly or indirectly through improving gut Data from the present study suggest a microbiome more health. However, the mechanisms by which these amendments affected by age than treatment (Figure 2A). Irrespective of work are poorly understood. Most claim to enhance health and treatment, all groups show a sharp decline in Enterobacteriaceae performance via manipulation of the host intestinal microbiome, with age, including the vaccinated groups, where levels of but the mechanism of action has been studied in very few of these Enterobacteriaceae would be expected to increase following products (24, 25). Salmonella (member of the Enterobacteriaceae family) vaccina- In the present study, we administered two commonly used live tion. Nor does addition of a Firmicutes-based probiotic product bacterial treatments applied in poultry production to enhance stimulate more rapid conversion to a Firmicutes-dominated intestinal health and function. According to the manufacturer, microbiome (Figure 2B) in probiotic-fed animals. Day-old birds the live ST vaccine used here is intended to prevent colonization begin with a gut colonized by few bacterial species at a concen- of the gut and internal organs by multiple types of Salmonella, tration several orders of magnitude lower than mature animals including Heidelberg, Typhimurium, Hadar, Kentucky, and (28, 29), so it is likely that the primary driver of age-dependent Enteritidis (26). Similarly, the probiotic used here is intended to increase in complexity is bacteria colonizing a previously empty maintain healthy microbiota balance in the gut (27). We investi- niche. However, diet can also play a major role in the composition gated to what extent these health-promoting treatments affect the of the microbiome and exerts an influence on the developing and microbiome of young chicks. mature gut (30, 31). Studies by Sergeant et al. characterizing the We found that the post-hatch intestinal microbiome has low microbiome of wheat-fed chickens reported Megamonas and diversity dominated by Gram-negative bacteria, particularly Negativicutes as more abundant in their adult birds, while the Enterobacteriaceae, which includes Salmonella, Klebsiella, Proteus, Firmicutes most commonly seen in this trial, Lachnospiraceae and Escherichia coli. During the first week of life, there is a shift and Ruminococcaceae, were less abundant (32). The effect of gut to a much more diverse community comprised of a wide variety development on the intestinal microbiome is more difficult to Frontiers in Veterinary Science | www.frontiersin.org 31 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome quantify; though studies of germ free and gnotobiotic mice clearly predicted increases in the VP group in genes related to motility, demonstrate that the microbiome is essential to the development flagellar assembly, chemotaxis, and two-component system. By of a fully functioning gut (33, 34), whether the developmental contrast, VP microbiomes displayed lower abundance of many stage of the gut is a variable influencing the development of the protein and energy metabolism genes, as well as genes related to microbiome is less clear. DNA replication and protein translation (Figure 4A). Supporting Despite the strong relationship between age and composi- the taxonomic data suggesting that the microbiome is still equili- tion of the microbiome, the bacterial treatments included brating at day 14 (Figures 2 and 3), the functional changes at day in this study did affect the microbiome. PCoA of the four 28 are both fewer and less dramatic (Figure 5). The VP group treatment groups at days 1, 7, 14, and 28 illustrate the impact exhibits the most variation of the four treatments, and suggests of both vaccination and probiotic supplementation on the changes in a few cellular metabolism pathways. Interestingly, the microbiome (Figure 3A). Despite the fact that the vaccine is effect of probiotic supplementation and its interaction with the only administered on day 0, global R statistics demonstrate vaccine appears to stimulate more functional changes than the that the impact of ST on the composition of the microbiome vaccine group alone. At days 14 and 28, the DP and VP groups is on par with that of the continuously fed probiotic at days 14 were more likely to have either the highest or lowest levels of any (vaccine = 0.802, probiotic = 0.882) and 28 (vaccine = 0.697, given gene group. probiotic = 0.705). The magnitude of the effect of the one-time A possible contributor to the lack of more dramatic functional ST inoculation is nearly as great as that of the continuously diversity between treatment groups at day 28 could be limitations fed probiotic despite low levels of the ST-containing taxonomic inherent to this technique and its application to avian microbial group Enterobacteriaceae after day 7, suggesting early coloniz- communities. One of these is its reliance on sequenced and anno- ers influence the relative abundance of the microbiome despite tated genomes. Though comparisons between PICRUSt results being transient themselves. While little is known about the and metagenomics data from the same samples have shown that long-term effects of early microbiome perturbation, some stud- the predictive value of PICRUSt analysis is very good (20, 41), 16S ies support this idea (35, 36). genes without a confident phylogenetic assignment cannot be used To understand the impact of treatment at the taxonomic as marker genes. Because of this, about 15% of the 16S sequences level, SIMPER was conducted to identify species contributing were filtered out at day 14 and over 20% at day 28. This number to differences between treated and untreated animals. Most of unknown or uncharacterized sequences may be higher in the of the differences between DC and treated animals at days 14 avian microbiome than in the human or murine microbiome, as and 28 involve Lachnospiraceae, Ruminococcaceae, and other the databases used in this process were all developed based on Clostridiales (Tables 1 and 2). Though abundance of Lactobacillus mammalian microbiota; chicken-specific microbes that may be in the DP and VP groups is higher at day 14 (P < 0.05), the important in this system could be excluded from analysis because magnitude of the increase in VP over DC is not great enough for they are not part of the 16s and/or KEGG databases. However, Lactobacillus to be a major source of dissimilarity. There is little this analytical technique has been successfully used on avian microbiological evidence that the bacterial products applied in microbiomes in the past (6). While the difference in excluded taxa this study interfere with each other; levels of Lactobacillus are not between time points is not large, it is possible that the bacteria significantly lower in the VP group than the DP group, and VP excluded from analysis are active in the community; evaluation animals remain ST-positive at day 28 (data not shown). There are of those taxa excluded from PICRUSt analysis indicates that some signs of treatment interaction; however, ST vaccination decreases are differentially abundant between treatment groups (Tables S3 abundance of the group Clostridiales Other, and the combination and S4 in Supplementary Material). These bacteria could play a of probiotic and vaccine results in the strongest difference from significant role in the activity of the microbiome. Bacteria falling the DP group; 11% reduced to 1% of the identified bacteria, under the Clostridiales Other group were consistently higher in perhaps indicating a synergy between the two treatments, which the DC group relative to other treatments, and could represent makes the cecum a more hostile environment for this group of an unmeasured source of functional differences between treat- bacteria. ment groups. However, their metagenomic contribution to the Changes in taxonomic diversity are the most used indicator community cannot be known without further characterization to infer changes in microbiological activity, but it is becoming of their genome. apparent that many of the functions of a normal microbiome can The relative lack of functional gene differences at day 28 could be carried out by a number of microbial groups (37, 38). Therefore, also be an indication that despite continuing taxonomic differ- understanding how treatments affect taxonomic abundance may ences, the microbiome in each treatment is converging toward a not provide us with a complete understanding of how they impact similar metabolic pattern. Conservation of function across a vari- healthy and diseased guts, or develop therapies that target the ety of microbial profiles has been described in other studies, and predominant cause of gut dysbiosis; a change in function. In its extreme dysregulation of the microbiome may be required before entirety, the chicken gut is estimated to be colonized by as many as severe or protracted functional changes occur (37). Figure 5 1013 microbes, and they have a combined genetic potential far in illustrates this concept; while the bacterial treatments applied in excess of the ~20,000 genes identified in the chicken genome (39, this study affect both the taxonomic and inferred metagenomic 40). PICRUSt uses the 16S rRNA genes obtained during sequenc- composition of the microbiome, even statistically significant ing to infer the presence of functional genes known or predicted changes in function gene content are minor when compared to to be associated with those 16S sequences. At day 14, there were the taxonomic changes seen in the same animals. Frontiers in Veterinary Science | www.frontiersin.org 32 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome In the present study, the chickens were all free of visible growth conditions. By contrast, as has been seen in other studies disease or stress, and it is possible their gut microbiota were (7), age played a major role in the composition and richness of functioning in their optimal range with or without treatment. the bacterial community. Major shifts from day of hatch to day 14 It is also important to note that these birds were not given a centered on the early dominance of Enterobacteriaceae, followed pathogen challenge or other stressor of any kind. The addition by a transition to Firmicutes-dominated ceca. Future studies will of vaccinations or probiotics to a chicken with a dysbiotic gut focus on understanding the functional and phylogenetic param- microbiome might yield more significant functional changes. eters of a normal developing microbiome, and to evaluate the Recent studies demonstrated that exposure of mice to antibiotics effect of treatments like these on that normal range of microbial at an early age can have a deleterious effect on the diversity of the profiles. microbiome for several months following treatment (42). This study showed no such effect from probiotic or vaccination. The ACKNOWLEDGMENTS value of select dietary treatments and management practices in poultry production may be their ability to increase the speed at The authors wish to thank Dr. Amy Savage, North Carolina State which a disturbed or stunted microbiome is able to return to a University for helpful discussions and input related to data analy- normal functional state. sis. AB was supported in part by NIFA National Needs Fellowship In conclusion, one-time oral inoculation with a live ST strain 2009-38420-05026, and generous gift from Star-Labs/Forage and daily ingestion of a probiotic feed supplement both alter Research, Inc. Additional support from NIFA Animal Health the microbiome of growing chicks. These differences persisted project Accession# 1001792. Microbiome 16S data deposited throughout the study, and are centered on changes in the abun- with Qiita (http://qiita.ucsd.edu/; study 10291). dance of core microbes present in all treatment groups. The results of this trial suggest that common bacterial treatments, such as SUPPLEMENTARY MATERIAL probiotics and bacterial vaccines, affect the taxonomic composi- tion of the microbiome, but only have transient or small effects on The Supplementary Material for this article can be found online the function and activity of the microbiome under non-stressed at http://journal.frontiersin.org/article/10.3389/fvets.2016.00002 REFERENCES rRNA gene-based environmental surveys. Appl Environ Microbiol (2009) 75:5227–36. doi:10.1128/AEM.00592-09 1. Mohan B, Kadirvel R, Natarajan A, Bhaskaran M. Effect of probiotic supple- 13. Aronesty E. ea-utils: command-line tools for processing biological sequencing mentation on growth, nitrogen utilisation and serum cholesterol in broilers. data. (2011). Available From: http://code.google.com/p/ea-utils Br Poult Sci (1996) 37:395–401. doi:10.1080/00071669608417870 14. Caporaso JG, Kuczynski J, Stombaugh J, Bittinger K, Bushman FD, Costello 2. Roos NM, de, Katan MB. Effects of probiotic bacteria on diarrhea, lipid EK, et al. QIIME allows analysis of high-throughput community sequencing metabolism, and carcinogenesis: a review of papers published between 1988 data. Nat Methods (2010) 7:335–6. doi:10.1038/nmeth.f.303 and 1998. Am J Clin Nutr (2000) 71:405–11. 15. Edgar RC. Search and clustering orders of magnitude faster than BLAST. 3. Marangon S, Busani L. The use of vaccination in poultry production. Rev Sci Bioinformatics (2010) 26:2460–1. doi:10.1093/bioinformatics/btq461 Tech (2007) 26:265–74. 16. DeSantis TZ, Hugenholtz P, Larsen N, Rojas M, Brodie EL, Keller K, et al. 4. Saif YM. Diseases of Poultry. Hoboken, NJ: Wiley (2003). Greengenes, a chimera-checked 16S rRNA gene database and workbench 5. Oakley BB, Lillehoj HS, Kogut MH, Kim WK, Maurer JJ, Pedroso A, et al. The compatible with ARB. Appl Environ Microbiol (2006) 72:5069–72. doi:10.1128/ chicken gastrointestinal microbiome. FEMS Microbiol Lett (2014) 360:100–12. AEM.03006-05 doi:10.1111/1574-6968.12608 17. Caporaso JG, Bittinger K, Bushman FD, DeSantis TZ, Andersen GL, Knight 6. Waite DW, Taylor MW. Characterizing the avian gut microbiota: membership, R. PyNAST: a flexible tool for aligning sequences to a template alignment. driving influences, and potential function. Front Microbiol (2014) 5:223. Bioinformatics (2010) 26:266–7. doi:10.1093/bioinformatics/btp636 doi:10.3389/fmicb.2014.00223 18. McDonald D, Price MN, Goodrich J, Nawrocki EP, DeSantis TZ, Probst A, 7. Oakley BB, Buhr RJ, Ritz CW, Kiepper BH, Berrang ME, Seal BS, et al. et al. An improved Greengenes taxonomy with explicit ranks for ecological Successional changes in the chicken cecal microbiome during 42 days of and evolutionary analyses of bacteria and archaea. ISME J (2012) 6:610–8. growth are independent of organic acid feed additives. BMC Vet Res (2014) doi:10.1038/ismej.2011.139 10:282. doi:10.1186/s12917-014-0282-8 19. Clarke KR, Gorley RN. PRIMER v6: User Manual/Tutorial. Plymouth: 8. Caporaso JG, Lauber CL, Walters WA, Berg-Lyons D, Huntley J, Fierer N, et al. PRIMER-E (2006). 192 p. Ultra-high-throughput microbial community analysis on the Illumina HiSeq 20. Langille MGI, Zaneveld J, Caporaso JG, McDonald D, Knights D, Reyes JA, and MiSeq platforms. ISME J (2012) 6:1621–4. doi:10.1038/ismej.2012.8 et al. Predictive functional profiling of microbial communities using 16S 9. David LA, Maurice CF, Carmody RN, Gootenberg DB, Button JE, Wolfe BE, rRNA marker gene sequences. Nat Biotechnol (2013) 31:814–21. doi:10.1038/ et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature nbt.2676 (2014) 505:559–63. doi:10.1038/nature12820 21. Kanehisa M, Goto S. KEGG: Kyoto encyclopedia of genes and genomes. 10. Hale VL, Tan CL, Knight R, Amato KR. Effect of preservation method on Nucleic Acids Res (2000) 28:27–30. doi:10.1093/nar/28.1.27 spider monkey (Ateles geoffroyi) fecal microbiota over 8 weeks. J Microbiol 22. Parks DH, Tyson GW, Hugenholtz P, Beiko RG. STAMP: statistical analysis Methods (2015) 113:16–26. doi:10.1016/j.mimet.2015.03.021 of taxonomic and functional profiles. Bioinformatics (2014) 30:3123–4. 11. Zhao L, Wang G, Siegel P, He C, Wang H, Zhao W, et al. Quantitative genetic doi:10.1093/bioinformatics/btu494 background of the host influences gut microbiomes in chickens. Sci Rep (2013) 23. Storey JD, Tibshirani R. Statistical significance for genomewide studies. Proc 3:1163. doi:10.1038/srep01163 Natl Acad Sci U S A (2003) 100:9440–5. doi:10.1073/pnas.1530509100 12. Youssef N, Sheik CS, Krumholz LR, Najar FZ, Roe BA, Elshahed MS. 24. Lee K, Lillehoj HS, Siragusa GR. Direct-fed microbials and their impact on Comparison of species richness estimates obtained using nearly complete the intestinal microflora and immune system of chickens. J Poult Sci (2010) fragments and simulated pyrosequencing-generated fragments in 16S 47:106–14. doi:10.2141/jpsa.009096 Frontiers in Veterinary Science | www.frontiersin.org 33 January 2016 | Volume 3 | Article 2 Ballou et al. Development of the Chick Microbiome 25. Neal-McKinney JM, Lu X, Duong T, Larson CL, Call DR, Shah DH, et al. 36. Jakobsson HE, Jernberg C, Andersson AF, Sjölund-Karlsson M, Jansson Production of organic acids by probiotic lactobacilli can be used to reduce JK, Engstrand L. Short-term antibiotic treatment has differing long-term pathogen load in poultry. PLoS One (2012) 7:e43928. doi:10.1371/journal. impacts on the human throat and gut microbiome. PLoS One (2010) 5:e9836. pone.0043928 doi:10.1371/journal.pone.0009836 26. Compendium NA. Compendium of Veterinary Products. 9th ed. Port Huron, 37. Consortium THMP. Structure, function and diversity of the healthy human MI: North American Compendiums, Incorporated (2006). microbiome. Nature (2012) 486:207–14. doi:10.1038/nature11234 27. PrimaLac. PrimaLac Direct-fed Microbials. (2015). Available From: http:// 38. Kurokawa K, Itoh T, Kuwahara T, Oshima K, Toh H, Toyoda A, et al. www.primalac.com Comparative metagenomics revealed commonly enriched gene sets in 28. Barnes EM, Impey CS, Cooper DM. Manipulation of the crop and intestinal human gut microbiomes. DNA Res (2007) 14:169–81. doi:10.1093/dnares/ flora of the newly hatched chick. Am J Clin Nutr (1980) 33:2426–33. dsm018 29. Lev M, Briggs CAE. The gut flora of the chick. I. the flora of newly hatched 39. Burt DW. Chicken genome: current status and future opportunities. Genome chicks. J Appl Bacteriol (1956) 19:36–8. doi:10.1111/j.1365-2672.1956. Res (2005) 15:1692–8. doi:10.1101/gr.4141805 tb00041.x 40. Salanitro JP, Blake IG, Muirehead PA, Maglio M, Goodman JR. Bacteria 30. Filippo CD, Cavalieri D, Paola MD, Ramazzotti M, Poullet JB, Massart S, et al. isolated from the duodenum, ileum, and cecum of young chicks. Appl Environ Impact of diet in shaping gut microbiota revealed by a comparative study Microbiol (1978) 35:782. in children from Europe and rural Africa. Proc Natl Acad Sci U S A (2010) 41. McHardy IH, Goudarzi M, Tong M, Ruegger PM, Schwager E, Weger JR, 107:14691–6. doi:10.1073/pnas.1005963107 et al. Integrative analysis of the microbiome and metabolome of the human 31. Turnbaugh PJ, Bäckhed F, Fulton L, Gordon JI. Diet-induced obesity is linked intestinal mucosal surface reveals exquisite inter-relationships. Microbiome to marked but reversible alterations in the mouse distal gut microbiome. Cell (2013) 1:17. doi:10.1186/2049-2618-1-17 Host Microbe (2008) 3:213–23. doi:10.1016/j.chom.2008.02.015 42. Nobel YR, Cox LM, Kirigin FF, Bokulich NA, Yamanishi S, Teitler I, et al. 32. Sergeant MJ, Constantinidou C, Cogan TA, Bedford MR, Penn CW, Pallen Metabolic and metagenomic outcomes from early-life pulsed antibiotic treat- MJ. Extensive microbial and functional diversity within the chicken cecal ment. Nat Commun (2015) 6:7486. doi:10.1038/ncomms8486 microbiome. PLoS One (2014) 9:e91941. doi:10.1371/journal.pone.0091941 33. Tlaskalová-Hogenová H, Štěpánková R, Kozáková H, Hudcovic T, Vannucci Conflict of Interest Statement: This research was funded in part through a gift L, Tučková L, et al. The role of gut microbiota (commensal bacteria) and from Star Labs Inc. (Clarksdale, MO, USA). Use of trade names in this publication the mucosal barrier in the pathogenesis of inflammatory and autoimmune does not imply endorsement by the North Carolina Agricultural Research Service diseases and cancer: contribution of germ-free and gnotobiotic animal or criticism of similar products not mentioned. models of human diseases. Cell Mol Immunol (2011) 8:110–20. doi:10.1038/ cmi.2010.67 Copyright © 2016 Ballou, Ali, Mendoza, Ellis, Hassan, Croom and Koci. This 34. Willing BP, Van Kessel AG. Intestinal microbiota differentially affect brush bor- is an open-access article distributed under the terms of the Creative Commons der enzyme activity and gene expression in the neonatal gnotobiotic pig. J Anim Attribution License (CC BY). The use, distribution or reproduction in other forums Physiol Anim Nutr (2009) 93:586–95. doi:10.1111/j.1439-0396.2008.00841.x is permitted, provided the original author(s) or licensor are credited and that the 35. Dominguez-Bello MG, Blaser MJ, Ley RE, Knight R. Development of the human original publication in this journal is cited, in accordance with accepted academic gastrointestinal microbiota and insights from high-throughput sequencing. practice. No use, distribution or reproduction is permitted which does not comply Gastroenterology (2011) 140:1713–9. doi:10.1053/j.gastro.2011.02.011 with these terms. Frontiers in Veterinary Science | www.frontiersin.org 34 January 2016 | Volume 3 | Article 2 Original Research published: 19 February 2016 doi: 10.3389/fvets.2016.00011 Spatial and Temporal Changes in the Broiler Chicken Cecal and Fecal Microbiomes and Correlations of Bacterial Taxa with Cytokine Gene Expression Brian B. Oakley1* and Michael H. Kogut2 1 College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, USA, 2 United States Department of Agriculture, Agricultural Research Service, Southern Plains Area Research Center, College Station, TX, USA To better understand the ecology of the poultry gastrointestinal (GI) microbiome and its interactions with the host, we compared GI bacterial communities by sample type (fecal or cecal), time (1, 3, and 6 weeks posthatch), and experimental pen (1, 2, 3, or 4), and measured cecal mRNA transcription of the cytokines IL18, IL1β, and IL6, Edited by: IL10, and TGF-β4. The microbiome was characterized by sequencing of 16S rRNA gene Paul Wigley, amplicons, and cytokine gene expression was measured by a panel of quantitative-PCR University of Liverpool, UK assays targeting mRNAs. Significant differences were observed in the microbiome by Reviewed by: Lisa Bielke, GI location (fecal versus cecal) and bird age as determined by permutational MANOVA Ohio State University, USA and UniFrac phylogenetic hypothesis tests. At 1-week posthatch, bacterial genera Peter Heegaard, National Veterinary Institute, Denmark significantly over-represented in fecal versus cecal samples included Gallibacterium and *Correspondence: Lactobacillus, while the genus Bacteroides was significantly more abundant in the cecum. Brian B. Oakley By 6-week posthatch, Clostridium and Caloramator (also a Clostridiales) sequence types [email protected] had increased significantly in the cecum and Lactobacillus remained over-represented in fecal samples. In the ceca, the relative abundance of sequences classified as Clostridium Specialty section: This article was submitted to increased by ca. 10-fold each sampling period from 0.1% at 1 week to 1% at 3 week Veterinary Infectious Diseases, and 18% at 6 week. Increasing community complexity through time were observed in a section of the journal Frontiers in Veterinary Science increased taxonomic richness and diversity. IL18 and IL1β significantly (p < 0.05, pairwise Received: 11 September 2015 t-tests) increased to maximum mean expression levels 1.5 fold greater at week 3 than Accepted: 04 February 2016 1, while IL6 significantly decreased to 0.8- and 0.5-fold expression at 3- and 6-week Published: 19 February 2016 posthatch, respectively relative to week 1. Transcription of pro-inflammatory cytokines Citation: was generally negatively correlated with the relative abundance of various members of Oakley BB and Kogut MH (2016) Spatial and Temporal Changes in the the phylum Firmicutes and positively correlated with Proteobacteria. Correlations of the Broiler Chicken Cecal and Fecal microbiome with specific cytokine mRNA transcription highlight the importance of the GI Microbiomes and Correlations of Bacterial Taxa with Cytokine Gene microbiome for bird health and productivity and may be a successful high-throughput Expression. strategy to identify bacterial taxa with specific immune-modulatory properties. Front. Vet. Sci. 3:11. doi: 10.3389/fvets.2016.00011 Keywords: microbiome and immune system, pro-inflammatory mediators, cytokines, cecum, succession Frontiers in Veterinary Science | www.frontiersin.org 35 February 2016 | Volume 3 | Article 11 Oakley and Kogut Cecal Microbiome Cytokine Correlations INTRODUCTION response or the development of immune homeostasis. The studies described here are the first attempt to bring insights into Poultry are naturally adapted to hosting a complex gastrointestinal interactions between the commensal microbiota and the expres- (GI) microbial community with hundreds of bacterial species and sion of regulatory cytokines in the chicken cecum over time by up to 1011 CFU per gram of gut contents (1). Benefits conferred by identifying specific taxa significantly correlated with cytokine this microbial community (the GI microbiome) include promot- gene expression. ing beneficial development of the intestinal mucus layer, epithelial In this work, we combine high-throughput sequencing of monolayer, and lamina propria (2, 3), excluding pathogenic taxa broad-range 16S rRNA gene amplicons with quantitative-PCR of (4), breaking down polysaccharides (5, 6), providing energy as cytokine gene expression to document differences in the GI micro- amino acids and short chain fatty acids (7, 8), and promoting biome according to sample type (fecal versus cecal) in the maturing proper development and homeostasis of the immune system (9). bird and examine correlations between specific taxa and measures However, until relatively recently, many important aspects of of cytokine gene expression. To our knowledge, paired cecal and the basic ecology of the poultry GI microbiome have remained fecal samples from individual birds have not been compared with hidden in a sort of black box due to technical limitations. With modern sequencing and phylogenetic methods nor have specific the use of high-throughput sequencing, we have begun to open bacterial taxonomic groups been correlated with cytokine mRNA this black box with important insights into the taxonomic transcription in local tissue in developing broilers. (10–16) and genomic (6, 17–19) composition of the poultry GI microbiome as summarized in several recent reviews (9, 20–22). From this growing body of knowledge, an important common MATERIALS AND METHODS finding has emerged detailing highly significant successional Experimental Design changes in the GI microbiome as birds mature. For example, At hatch, non-vaccinated broiler chicks with identical genetic in the chicken ceca, taxonomic richness and diversity typically backgrounds were obtained from a commercial breeder and increase from day of hatch to market age of commercial broilers placed into four floor pens. The birds were fed a balanced, unmedi- at 6 weeks as a community develops comprised almost exclusively cated corn, soybean meal-based starter (0–14 days), grower of bacteria belonging to the phylum Firmicutes (15). Enough data (15–30 days), and finisher (31–42 days) diet. At each of three are now available to also compare communities sampled from time points, fecal samples were collected from a total of 20 birds different anatomical regions of the GI tract. For example, relative (five from each of the four pens) that were then euthanized and to cecal communities, fecal samples typically contain higher rela- intestinal samples collected via necropsy. Intestinal mucosal and tive proportions and absolute abundance of bacteria belonging to luminal samples were collected from the cecum. Fecal contents the Enterobacteriales and Lactobacillales (9, 16, 20–22). Proper and intestinal samples were stored aseptically at −20°C. Time understanding of temporal and spatial changes in the chicken GI points sampled followed changes in diet from starter to grower microbiome is critically important for designing probiotic sup- feed, and grower to finisher feed. The experiment concluded at plements, monitoring gut health, and choosing sample types to day 42. These samples are referred to as weeks 1, 3, and 6. assess feed additive effects or pathogen shedding. Experiments were conducted according to the regulations The establishment of a normal microbiota constitutes a key established by the U.S. Department of Agriculture Animal Care component of gut health, through colonization resistance mecha- and Use Committee (ACUC # 2015003). Chicks were placed in nisms, and has implications for proper development of the gut floor pens containing clean wood shavings, provided supplemen- and full maturation of the mucosal immune system (9, 23). The tal heat, water, and a balanced, unmedicated corn and soybean communication between the microbiota and the immune system meal-based chick starter diet ad libitum that met or exceeded the is principally mediated by interaction between microbes and levels of critical nutrients recommended by the National Research pattern recognition receptors (PRRs) expressed by the intestinal Council (29). Salmonella was not detected in the feed or from the epithelium and various local antigen-presenting cells, resulting paper tray liners using standard analytical procedures (30). in activation or modulation of both innate and adaptive immune responses (23, 24). The composition of the GI microbiota is known to affect many host functions including nutrient utilization, gut Sample Collection for mRNA epithelium feeding, and the development and activity of the Chickens from each experimental group were euthanized at weeks gut immune system (25). The interaction between the immune 1, 3, and 6. A 25-mg piece of tissue was removed from the cecal system of the gut and commensal microbiota in chickens starts tonsils and was washed in PBS, placed in a 2-ml microcentrifuge immediately after hatching and leads to a low-level of inflam- tube with 1 ml of RNAlater (Qiagen, Inc., Valencia, CA, USA), mation characterized by an increased cytokine and chemokine and stored at −20°C until processed. expression as well as a number of immune-associated proteins (24, 26). As a result, there is an infiltration of heterophils and RNA Isolation lymphocytes into the lamina propria or the gut epithelium and Cecal tissues (25 mg) were removed from RNAlater and trans- normalization of the gut immune system (27, 28). However, to ferred to pre-filled 2-ml tube containing Triple-Pure™ 1.5-mm date, there has been no attempt to show an association between zirconium beads. RLT lysis buffer (600 μl) from the RNeasy mini kit the development of specific commensals in the chicken gut (Qiagen) was added, and the tissue was homogenized for 1–2 min with either the development of an efficient mucosal immune at 4,000 rpm in a Bead Bug microtube homogenizer (Benchmark Frontiers in Veterinary Science | www.frontiersin.org 36 February 2016 | Volume 3 | Article 11 Oakley and Kogut Cecal Microbiome Cytokine Correlations Scientific, Inc., Edison, NJ, USA). Total RNA was extracted from between samples within the experiment, the correction factor for the homogenized lysates according to the manufacturer’s instruc- each sample was calculated by dividing the mean threshold cycle tions, eluted with 50 μl RNase-free water, and stored at −80°C (CT) value for 28S rRNA-specific product for each sample by the until qRT-PCR analyses were performed. RNA was quantified overall mean CT value for the 28S rRNA-specific product from all and the quality evaluated using a spectrophotometer (NanoDrop samples. The corrected cytokine mean was calculated as follows: Products, Wilmington, DE, USA). average of each replicate × cytokine slope/28S slope × 28S correc- tion factor. The data shown are corrected 40 Ct values. Quantitative Real-Time PCR Primer and probe sets for the cytokines and 28S rRNA were 16S rRNA Sequencing and Data Analysis designed using the Primer Express Software program (Applied DNA was extracted from cecal samples using the MoBio Biosystems, Foster City, CA, USA) as previously described UltraClean Soil DNA extraction kit and DNA quality and and validated (31–33) and listed in Table 1. The qRT-PCR was concentration checked by spectrophotometry (NanoDrop performed using the TaqMan fast universal PCR master mix and Products, Wilmington, DE, USA). PCR and pyrosequencing of one-step RT-PCR master mix reagents (Applied Biosystems). the V1–V3 regions of 16S rRNA genes were performed using Amplification and detection of specific products were performed tagged amplicon methods with Roche 454 Titanium chemistry at using the Applied Biosystems 7500 Fast real-time PCR system Research and Testing Laboratory (Lubbock, TX, USA) as previ- as described previously (25, 26) with the following cycle profile: ously described (15, 34, 35). Following sequencing, sequences one cycle of 48°C for 30 min and 95°C for 20 s and 40 cycles were de-multiplexed and preprocessed with the Galaxy toolkit of 95°C for 3 s and 60°C for 30 s. Quantification was based on (36) and custom Perl, R, and shell scripts (37); additional quality the increased fluorescence detected by the 7500 Fast sequence controls according to standard protocols (38) were completed detection system due to hydrolysis of the target-specific probes by by trimming tag sequences, screening for presence of the for- the 5′-nuclease activity of the rTth DNA polymerase during PCR ward PCR primer sequence, and removing sequences with any amplification. Normalization was carried out using 28S rRNA ambiguous base calls. Based on expected amplicon sizes and as a normalizer gene. To correct for differences in RNA levels frequency distributions of sequence lengths in v115 of the Silva reference database, sequences were further limited to a range of Table 1 | Real-time quantitative RT-PCR probes and primers for pro- and 325–425 bp. Putative chimeric sequences were identified with anti-inflammatory cytokines. usearch (39) and ChimeraSlayer in mothur (40). Taxonomic classifications of sequences were performed in two RNA Probe/primer sequence Accession target numbera ways. First with the RDP naive Bayesian classifier (41) v2.6 and second with usearch with the global alignment option (39) using 28S Probe 5′-(FAM)-AGGACCGCTACGGACCTCCACCA X59733 the EMBL taxonomy from v115 of the Silva project curated seed -(TAMRA)-3′ database (42). To assess phylotype richness (number of taxa) and Fb 5′-GGCGAAGCCAGAGGAAACT-3′ Rc 5′-GACGACCGATTGCACGTC-3′ diversity [number of taxa weighted by relative abundance per the Shannon diversity index (43)] independent of taxonomic classifi- IL-1β Probe 5′-(FAM)- AJ245728 CCACACTGCAGCTGGAGGAAGCC- cations, sequences, which passed all the screens described above (TAMRA)-3′ were grouped into similarity clusters (operational taxonomic F 5′-GCTCTACATGTCGTGTGTGATGAG-3′ units; OTUs) using similarity cutoffs of 90, 95, and 97% with R 5′-TGTCGATGTCCCGCATGA-3′ uclust (39). The output from usearch provided the inputs for our IL-6 Probe 5′-(FAM)- AJ250838 own customized analysis pipeline to parse the clustering results AGGAGAAATGCCTGACGAAGCTCTCCA- and produce graphical and statistical summaries of the data for (TAMRA)-3′ the desired sampling units using perl and R (44) as previously F 5′-GCTCGCCGGCTTCGA-3′ R 5′-GGTAGGTCTGAAAGGCGAACAG-3′ described (35, 37). Clustering of communities was performed using the CCA function of the vegan package (45) in R based on IL-18 Probe 5′-(FAM)-CCGCGCCTTCAAGCAGGGATG- AJ416937 (TAMRA)-3′ OTU and taxonomic classifications. F 5′-AGGTGAAATCTGGCAGTGGAAT-3′ The relative effects of GI location (fecal versus cecal samples) R 5′-ACCTGGACGCTGAATGCAA-3′ and time (number of days posthatch) versus experimental treat- IL-10 Probe 5′ (FAM)-CGACGATGCGGCGCTGTCA- AJ621735 ment (and their interactive effects) on microbial communities (TAMRA)-3′ was determined by a permutational multivariate analysis of vari- F 5′-CATGCTGCTGGGCCTGAA-3′ ance (MANOVA) using the adonis function of the vegan package R 5′-CGTCTCCTTGATCTGCTTGATG-3′ in R. Either OTU or taxonomic classifications of sequences from TGF-β4 Probe 5′-(FAM)- M31160 each bird were used to partition sums of squared deviations ACCCAAAGGTTATATGGCCAACTTCTGCAT- from centroids in a distance matrix to determine how variation (TAMRA)-3′ F 5′-AGGATCTGCAGTGGAAGTGGAT-3′ was explained by experimental treatments or uncontrolled R 5′-CCCCGGGGTTGTGTGTTGGT-3′ covariates (46). Unifrac (47) implemented in mother (40) was used to compare the phylogenetic distribution of sequences for a Genomic DNA sequence. b Forward. each bird by comparing phylogenetic branch lengths shared or c Reverse. unique to each sample type of the experimentally derived tree Frontiers in Veterinary Science | www.frontiersin.org 37 February 2016 | Volume 3 | Article 11 Oakley and Kogut Cecal Microbiome Cytokine Correlations to a null distribution of samples randomly shuffled within the partition variance of distance matrices by sample location and same tree. bird age. For all classification approaches, both sampling location To compare cytokine gene expression among and between and bird age (and their interactive effects) were highly significant time points, ANOVA and post hoc pairwise t-tests were per- explanatory variables (Table 2). formed. To search for taxa with significant positive or negative Next, to further test the hypothesis that different sets of correlations with cytokine gene expression, slices of the dataset bacteria are found in fecal versus cecal samples, we compared were taken to generate Pearson correlation coefficients and lin- the phylogenetic distribution of sequences for each bird using ear regression models for the relative abundance of each taxon the unifrac statistic (47) as described in the Section “Materials versus cytokine expression values for a given bird at a given time and Methods.” Beginning at 1 week of age, the phylogenetic point. All phyla and genera were compared against each cytokine distributions of sequences from fecal versus cecal samples were expression profile for each time point; cutoffs of Pearson correla- highly significantly different (Figure 1). Of the 20 birds sampled tion coefficients >0.4 and r2 values >0.3 were chosen based on at 1 week of age, 18 birds had sufficient sequence data from both empirical testing. fecal and cecal samples to make this phylogenetic comparison RESULTS Table 2 | Permutational ANOVA results partitioning effects of bird age and sample type (cecal or fecal) on microbial community composition as Spatial Differences in Microbiome calculated at a 95% OTU cutoff as described in the text. Significant differences were observed in the microbiome depend- Degrees of Sums of Mean F Pr (>F) ing on sampling location (fecal versus cecal) and bird age (1, 3, freedom squares squares or 6 weeks of age) using a variety of metrics. First, we used a variety of taxonomic classifications (e.g., phylum or genus-level Age 2 8.53 4.26 20.91 <0.0001 Sample type 1 3.14 3.14 15.39 <0.0001 classifications with the Silva or RDP taxonomy) or taxonomic- Age:type 2 1.40 0.70 3.45 <0.0001 independent classifications (binning sequences into sequence- Residuals 110 22.43 0.20 similarity groups or operational taxonomic units; OTUs) to Total 115 35.51 Figure 1 | Phylogenetic clustering of cecal versus fecal bacterial communities from birds at 1 week of age (n = 18). Each circle represents a phylogenetic tree of cecal and fecal samples taken from a single bird. For each bird, 250 sequences were randomly sampled from each sample type, phylogenies constructed in ARB, and unique versus shared branch lengths compared using Unifrac as described in the methods section. All comparisons were highly significant (p < 0.0001; indicative of phylogenetic clustering) except for bird 4_5 shown in the lower right (p = 0.054). Results for weeks 3 and 6 showed similar results. Comparisons of genera significantly over-represented in fecal samples relative to cecal samples showed Lactobacillus and Gallibacterium were the most abundant while the genera Bacteroides, Pseudoflavonifractor, Oscillibacter, Flavonifractor, and Subdoligranulum were significantly more abundant in the ceca than in feces. Frontiers in Veterinary Science | www.frontiersin.org 38 February 2016 | Volume 3 | Article 11 Oakley and Kogut Cecal Microbiome Cytokine Correlations and only one bird had marginally (p = 0.05) different communi- “Materials and Methods.” Because of the significant differences in ties in fecal versus cecal samples while all other comparisons were the cecal versus fecal communities shown above, we performed highly significant (p < 0.0001; Figure 1). For each of the two other these analyses separately for each sample type. For the cecal time points (3 and 6 weeks of age), the results were essentially communities, the samples were clearly clustered according to identical with only one non-significant difference (p = 0.09) for bird age (Figure 2A) while the communities in the fecal samples one 6-week-old bird (data not shown). Bacteria inhabiting the were more variable with age-related differences less obvious ceca are clearly very different than those collected from fecal (Figure 2B). Permutational ANOVA of the distance matrices droppings excreted through the cloaca. used for these ordinations showed that bird age was a significant Several genera were identified with significantly different explanatory variable for the variance of both cecal and fecal representations in fecal versus cecal samples using metastats (data communities while experimental pen had non-significant effects not shown). At 1 week posthatch, two bacterial genera were sig- (Tables 3 and 4). nificantly over-represented in fecal samples relative to cecal sam- At a phylum level, clear changes could be seen in the micro- ples, Lactobacillus and Gallibacterium, present at 15- and 5-fold bial communities as the birds aged (Figure 3). At 1 week of age, greater relative abundance respectively. In the ceca, the genera Bacteroides were common in the ceca, ranging from 5 to 40% Bacteroides, Pseudoflavonifractor, Oscillibacter, Flavonifractor, relative abundance (Figure 3A). In the feces, Bacteroides were less and Subdoligranulum (the latter four all in the Clostridiales fam- common and abundant with only 6/19 birds having >10% relative ily) were significantly more abundant (2.5- to 3.5-fold) than in abundance of Bacteroides (Figure 3B). More than half of the birds fecal samples. By 6-week posthatch, Clostridium and Caloramator had at least 10% Proteobacteria, with a maximum exceeding 80% (also a Clostridiales) sequence types had increased significantly in one bird (Figure 3B). By 3 weeks of age, the same two birds in the cecum and Lactobacillus remained over-represented in had >20% Bacteroides in the cecal and fecal communities, but in fecal samples. all other samples, Firmicutes exceeded 80% relative abundance (Figure 3). Temporal Changes in Microbiome Significant changes through time for both cecal and fecal Next, to assess how the microbial communities in the ceca communities were also observed in richness and diversity and feces change through time during the 6 weeks of growth indices (Figure 4). At a 95% OTU level (roughly equivalent to to market age, we first clustered sequences with an ordination a genus-level classification) there was a significant increase in approach (correspondence analysis; cca) as described in Section both richness and diversity in 6-week-old birds compared to Figure 2 | Clustering of cecal [(A), n = 59] and fecal [(B), n = 57] communities by bird age (weeks 1, 3, 6) or pen (1, 2, 3, 4). Each point represents the community from a single bird using 95% OTU classifications as described in the text. Clustering and environmental fitting of bird age was performed with the cca function in R; labels indicate the centroids of each bird age with vectors indicating the direction and magnitude of influence of the bird age relative to the axes. Table 3 | Permutational ANOVA results partitioning effects of bird age Table 4 | Permutational ANOVA results partitioning effects of bird age and experimental pen on microbial community composition as calculated and experimental pen on microbial community composition as calculated at a 95% OTU cutoff as described in the text for cecal samples. at a 95% OTU cutoff as described in the text for fecal samples. Degrees of Sums of Mean F Pr (>F) Degrees of Sums of Mean F Pr (>F) freedom squares squares freedom squares squares Age 2 6.38 3.19 29.51 0.0001 Age 2 3.31 1.66 5.95 0.001 Pen 3 0.50 0.17 1.53 0.0963 Pen 3 1.02 0.34 1.23 0.204 Age:pen 6 1.04 0.17 1.60 0.0410 Age:pen 6 2.12 0.35 1.27 0.124 Residuals 47 5.08 0.11 Residuals 45 12.54 0.27 Total 58 13.00 Total 56 19.00 Frontiers in Veterinary Science | www.frontiersin.org 39 February 2016 | Volume 3 | Article 11
Enter the password to open this PDF file:
-
-
-
-
-
-
-
-
-
-
-
-