Does the rumen microbiome play a role in feed efficiency of beef cattle?1

Many factors can affect animal feed efficiency which is one of the important economic traits in the beef industry. To date, our understanding of the role of the rumen microbiota and its impact on feed efficiency is largely unknown. The objective of this paper was to determine if the rumen microbiota is associated with residual feed intake (RFI) by studying the metatranscriptome of the rumen microbiome from cattle with different RFI values. The microbial transcriptome profiles revealed that Succinivibrionaceae and Methanomassiliicoccales were the most active microbial phylotypes, occupying approximately 44.1% and 35.6% of the bacterial and archaeal communities in the rumen of steers fed with barley-based diet, respectively. Further, the relative abundance of Lachnospiraceae, Veillonellaceae, and p-2534–18B5 bacterial families and Methanomassiliicoccales archaeal taxa were different between low RFI (L-RFI; efficient) and high RFI (H-RFI; inefficient) beef steers. The microbiome of L-RFI animals possessed characteristics associated with higher metabolic function and cell survivability, suggesting that enhanced fermentation capacity and adaptability of the microbiome may be key factors to improve nutrient availability. Our results provide evidence that the rumen microbiome could be one of the biological factors associated with variation in cattle feed efficiency.