The microbiome and animal health

Abstract Text:

For monogastrics, the linkage between the microbiome and animal health has been established, and it is known that colonization of the gastrointestinal tract (GIT) stimulates development of the immune system. In ruminants, the microbiome has largely been evaluated to assess the potential contribution towards feed digestion and adaptive responses as a consequence of dietary change. For example, previous research has shown a positive relationship between the Firmicutes:Bacteroidetes ratio and milk fat yield, and that the abundance of Clostridiales (family VIII) is negatively associated with feed conversion. A positive association for the systemic acute phase response caused by a severe form of subacute ruminal acidosis and the prevalence of Escherichia coli in the rumen has also been reported. Separating cause and effect continue to be a challenge with this area of research. The ruminal microbiome is responsive to diet and changes are particularly evident when comparing high-forage and high-grain feeding scenarios. That said, there is evidence to suggest that the microbial community is relatively resistant to change and can revert back to a composition similar to the original community structure after being disturbed. The microbiome robustness presents a challenge when modifications to the community structure may be desired. Moreover, differences between the digesta associated versus mucosa and epithelia associated communities are present and these communities change throughout the GIT. While understanding the rumen microbiome is important, more distal regions of the GIT have not been thoroughly examined. The change in microbial community structure along the GIT may not be that surprising given changes in retention time and substrate availability. In addition, microbial-host crosstalk mechanisms may differ among regions helping to explain why the microbial community structure differs. Understanding the regulation of the microbial-host communication may provide the necessary information to develop practical strategies to modulate the microbial community structure. Accordingly, evaluating strategies to manipulate microbial colonization and succession in pre-ruminants appears to be a logical intervention strategy. In addition to the core microbiome, diversity of the microbiome appears to be a critical aspect and calves that develop scours have been reported to have lower diversity when evaluating the fecal microbiome. Thus, a systematic approach to improve our understanding of the relationship between microbiome, or at least key species, is needed to advance this area. Such research will require an in depth understanding of both the microbiome and host gastrointestinal physiology.

Keywords: gastrointestinal tract, microbiome, cattle