Cecum microbial communities from steers differing in feed efficiency1,2,3

Apart from the rumen, limited knowledge exists regarding the structure and function of bacterial communities within the gastrointestinal tract and their association with beef cattle feed efficiency. The objective of this study was to characterize the microbial communities of the cecum among steers differing in feed efficiency. Within 2 contemporary groups of steers, individual feed intake and BW gain were determined from animals fed the same diet. Within both of 2 contemporary groups, BW was regressed on feed intake and 4 steers within each Cartesian quadrant were sampled (n = 16/group). Bacterial 16S rRNA gene amplicons were sequenced from the cecal content using next-generation sequencing technology. No significant changes in diversity or richness were detected among quadrants, and UniFrac principal coordinate analysis did not show any differences among quadrants for microbial communities within the cecum. The relative abundances of microbial populations and operational taxonomic units revealed significant differences among feed efficiency groups (P < 0.05). Firmicutes was the dominant cecal phylum in all groups and accounted for up to 81% of the populations among samples. Populations were also dominated by families Ruminococcaceae, Lachnospiraceae, and Clostridiaceae, with significant shifts in the relative abundance of taxa among feed efficiency groups, including families Ruminococcaceae (P = 0.040), Lachnospiraceae (P = 0.020), Erysipelotrichaceae (P = 0.046), and Clostridiaceae (P = 0.043) and genera Coprobacillus (P = 0.049), Parabacteroides (P = 0.044), Blautia (P = 0.042), Ruminococcus (P = 0.040), Oscillospira (P = 0.042), and Prevotella (P = 0.042). The study identified cecal microbial associations with feed efficiency, ADG, and ADFI. This study suggests an association of the cecum microbial community with bovine feed efficiency at the 16S level.