ruminAnt nutrition: syMPOsiuM: The ruMen MicrOBiOMe and nuTriTiOnal healTh and PrOducTiOn

The linkage among the microbial community and health outcomes in monogastric species has been well documented along with demonstrated evidence for species-dependent health consequences. While a symbiotic relationship between the microbial inhabitants and the ruminant host has been accepted from the perspective of feed digestion, the mechanisms for host-regulation of the microbial community is not well understood and the influence of individual microbial species on health outcomes has been poorly defined. Major challenges include understanding the structure of the digesta associated and epimural populations and how these populations change across the gastrointestinal tract. Current research efforts are examining the establishment of the microbiome in newborn calves to gain an improved understanding of the colonization process. It is currently accepted that the dominant phyla within the microbiome consist of firmicutes, bacteroidetes, and proteobacteria and that these remain relatively stable for most of a healthy cow’s life. However, variations in the composition, proportion, and functional properties of the rumen and intestinal microbiomes exist among individuals. To help understand the relationship between the microbiome and animal health, ruminal acidosis induction protocols have developed and proven to be an excellent model. In fact, it has been demonstrated that changes in the microbial community structure, specifically and increase in Escherichia coli, can be related to the systemic immune response induced by ruminal acidosis. However, it is still not clear whether the translocation of antigens induced by ruminal acidosis occurs in the reticulo-rumen or more distally in the gastrointestinal tract. The latter is especially important given the large changes in epithelial barrier function and marked changes in the concentration of lipopolysaccharide across the gastrointestinal tract. An in depth understanding of both the microbiome and host gastrointestinal physiology is key to addressing this challenging area.