show Abstracthide AbstractIn the present study, rumen microbiomes of beef cattle from three breeds (Angus, Charolais, Kinsella composite hybrid) with high and low feed efficiency were explored using metagenomics and metatranscriptomics, aiming to identify differences between functional potentials and activities of same rumen microbiomes, and to evaluate the effects of host breed and feed efficiency on the rumen microbiome in various cattle breeds.