Location: Agroecosystem Management ResearchTitle: Tracking bacteria through the entire gastrointestinal tract of a beef steer Author
Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2017
Publication Date: 8/17/2017
Citation: Durso, L.M., Miller, D.N., Schmidt, T.B, Callaway, T.R. 2017. Tracking bacteria through the entire gastrointestinal tract of a beef steer. Agricultural and Environmental Letters. 2:170016. doi:10.2134/ael2017.05.0016.
DOI: https://doi.org/10.2134/ael2017.05.0016 Interpretive Summary: Fecal-borne bacteria play a dynamic role in livestock agricultural systems. They cycle nutrients, emit gaseous, sometimes odorous, compounds, contribute to the animal’s health by impacting the immune system status, and serve as a source for zoonotic pathogens and antibiotic resistant bacteria. The feces represents an end product of a series of sequential bio-reactions occurring along the entire cattle gastrointestinal tract (GIT). The beef cattle GIT is a series of dynamic selective environments, from mouth to anus where a wide range of fermentative biochemical reactions convert complex feedstuff into components necessary for animal growth. The digestive tract is structured so that the output from one compartment serves as the input for the subsequent compartment. Both host animal physiological factors and substrate availability create a set of unique selective pressures in each of these compartments that influence which bacteria are enriched in each compartment. In this study, we characterized the bacteria along the entire length of the GIT. We found that the number of bacteria shared between neighboring compartments varied – with high numbers of shared bacteria in the rumen and fermentative parts of the GIT, but a much smaller amount shared between the stomach and the small intestine. Of the bacteria that were observed in the oral cavity, only 4% were also observed at the end of the GIT. These results provide insight into microbial spatial relationships along the beef cattle GIT.
Technical Abstract: Biological processes within beef-cattle gastrointestinal tracts (GIT) influence animal health, while the output (feces), is an important vehicle for both zoonotic pathogens and antibiotic resistant bacteria. Although microbes in individual components of GIT have been extensively characterized, a whole-system microbial community census may reveal unrecognized relationships. Here we characterize bacteria from 16 GIT sites within a beef steer, and examine the proportion of bacteria contributed by upstream compartments. This animal displayed characteristic differences between tissue and ingesta communities in gastric and large-intestine samples. Up to 81% of operational taxonomic units (OTUs) were shared among neighboring gastric compartments, compared to 50% shared between abomasum and duodenum. It is unclear whether this reflects a decrease in bacterial number, or rapid multiplication of certain taxa. Only 4% of rectal OTUs were originally observed in the oral cavity.