Ruminal bacterial community composition in dairy cows is dynamic over the course of two lactations and correlates with feed efficiency

Authors: JEWELL, KELSEA - University Of Wisconsin; MCCORMICK, CAROLINE - University Of Wisconsin; Odt, Christine; Weimer, Paul; SUEN, GARRET - University Of Wisconsin

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2015
Publication Date: 6/19/2015
Publication URL: https://handle.nal.usda.gov/10113/62064
Citation: Jewell, K.A., McCormick, C., Odt, C.L., Weimer, P.J., Suen, G. 2015. Ruminal bacterial community composition in dairy cows is dynamic over the course of two lactations and correlates with feed efficiency. Applied and Environmental Microbiology. 81:4697-4710.

Interpretive Summary: Dairy cows rely on the microbial community in their rumen to ferment feeds to products the cow can use for energy, growth, and milk production; however, little work has been done to relate the efficiency of milk production to specific members of the microbial community. We measured milk production efficiency (milk produced divided by feed consumed) in a group of Holstein cows over two lactation cycles. We then characterized the microbial communities in two groups of cows that differed in efficiency. From this analysis, we identified a collection of over two dozen bacterial species whose abundance in the community differed between the two groups of cows. In the effort to improve milk production efficiency, these results will be useful in future studies targeted toward determining the specific contribution of individual bacterial species to milk production by the cow.

Technical Abstract: A group of 14 Holstein cows of similar age were followed through the course of their first two lactation cycles. During each lactation cycle, ruminal solids and liquids, milk samples and production data, and feed consumption data were collected for each cow during Early (76-82 days in milk, DIM), Middle (151-157 DIM), and Late (251-257 DIM) lactation periods. The bacterial community composition of each ruminal sample was determined by sequencing the 16S rRNA gene using 454 pyrosequencing. Gross feed efficiency (GFE) for each cow was calculated by dividing her energy-corrected milk by dry matter intake (ECM/DMI) for each period of both lactation cycles. The most abundant phyla detected for all cows were the Bacteroidetes, Firmicutes, Proteobacteria, and Tenericutes. The most abundant members shared amongst all animals were in the genus Prevotella, and the other shared community members included members of the genera Ruminococcus and Coprococcus, among others. The communities of the solid and liquid phases were significantly different, but the bacterial microbiota between the first and second lactation cycles were highly similar. Moreover, the diversity increased significantly over the course of the two lactations. From this cohort, four pairs of cows were identified that differed in milk production efficiency as defined by residual feed intake (RFI) at the same level of ECM production. There was a significant correlation between total community composition and GFE. Specific OTUs were identified whose relative sequence abundance displayed significant positive or negative correlation with GFE or RFI. These data suggested that the ruminal bacterial community is dynamic in terms of membership and diversity, and that specific members are associated with high- and low-milk production efficiency over multiple lactation cycles.