Rumen microbiome and fat deposition in sheep: insights from a bidirectional mendelian randomization study

Rumen microbiotas are known to influence the fat deposition ( FD ) in sheep, but controversy over causality remains unresolved. Here, we performed microbiome-wide association studies ( MWAS ), microbiome genome-wide association analysis ( mbGWAS ) and bidirectional mendelian randomization ( MR ) analyses on 1,150 sheep with genotype data from whole-genome resequencing, 16S rRNA sequencing and multilevel FD-traits data. We quantified the proportion of individual variation in FD-traits explained by host genetics, rumen microbiota, and their interaction effects. We identified 32 rumen microbiota biomarkers including Bifidobacterium that were associated with FD-traits (P adj