FECAL MICROBIOTA COMPOSITION OF NELLORE STEERS WITH HIGH AND LOW FEED EFFICIENCY PHENOTYPES Raw sequence reads

Nutritionists and animal breeders aiming to improve the production performance and reduce the environmental impact (largely due to methane emissions) of cattle herds have been investigating the feed efficiency phenotype of beef and dairy cattle. Anaerobic microorganisms that inhabit the digestive tract of ruminants establishing a symbiotic relationship are largely responsible for the degradation of complex fiber sources, allowing the ruminants to harness the essential nutrients of the ingested food, in addition to obtaining greater energy. In this work, the aim was to evaluate if the fecal microbiota of Nellore cattle could be used as an indicator of feed efficiency for beef cattle. Fifty-nine Nellore steers, comprising 29 animals showing negative (high feed-efficiency, n-RFI) and 30 showing positive (low feed-efficiency, p-RFI) residual feed intake (RFI), were selected for this study. Fecal samples were collected, genomic DNA was extracted and the 16S rRNA was amplified and paired-end reads were generated via Illumina MiSeq sequencing. Metataxonomic analyses indicated significant differences in species richness (Chao-1) and diversity (Shannon) between the fecal microbiota of n-RFI and p-RFI steers (Mann-Whitney test, p<0.05). Firmicutes and Bacteroidetes were the most abundant phyla in the fecal-associated microbiota of Nellore steers and members of the genera Ruminococcaceae_UCG-014, dgA-11_gut_group, Treponema_2 e Slackia showed significant differences in fecal samples from the n-RFI and p-RFI groups. Otu00008 (Roseburia spp.) showed the highest abundance among OTUs with significant differences between the efficiency groups, being more abundant in the n-RFI group. These bacterial groups could be useful as potential biomarkers of the feed efficiency phenotype in Nellore cattle. However, further confirmatory studies will be needed to validate these findings using larger cohorts of animals in a commercial scale.