Characterization of whole blood and hepatic mRNA expression of immune genes and rumen bacterial community of crossbred beef steers with divergent residual feed intake phenotypes

We investigated rumen microbiota of crossbred beef steers with divergent residual feed intake phenotypes to identify relevant biological processes underpinning feed efficiency in beef cattle. Low-RFI beef steers and high-RFI beef steers were selected from a group of 108 growing crossbred beef steers fed a high-forage total mixed ration after a 49-d performance testing period. At the end of the 49-d testing period, rumen fluid samples were collected for analysis of the rumen bacterial community. The relative abundance of PeH15, Arthrobacter, Moryella, Weissella and Muribaculaceae were enriched in low-RFI steers, while Methanobrevibacter, Bacteroidales_BS11_gut_group, and Bacteroides were reduced.