The aim was to examine the relationship between extreme RFI phenotypes and the taxonomic and functional profiles of the rumen microbiome in fattening Charolais bulls. Briefly, the study consisted of a cohort of 100 growing Charolais bulls (382±41 kg live weight and 259±42 days old at the start of the experiment) that were fed corn silage (CS)- or grass silage (GS)- based diets from two independent batches (experimental years 2019 [n = 50 bulls] and 2020 [n = 50 bulls]). Following a four-week period of adaptation to the facilities and their experimental diet, the feed efficiency of all bulls was evaluated over an 84-day period. In each batch (experimental year), the results of this feed efficiency test allowed for the classification of the bulls within each diet according to their RFI value, resulting in a total of 32 most extreme bulls (four for each batch and diet).

QUIIME, 2