371. Evidence of Genetic Links Between Rumen Bacteria and Milk Somatic Cell Score in Lacaune Dairy Sheep

Mastitis is a high prevalence infectious disease in dairy sheep. Even if selection by milk somatic cell score (SCS) has been implemented to increase mastitis resistance, we wonder if rumen bacteria could influence udder inflammatory response. The objectives are to estimate genetic correlations between rumen bacteria and average SCS over lactation (LSCS), and to identify underlying mechanism between traits. 795 Lacaune ewes were studied using metabarcoding (16S rRNA gene) for rumen bacteria characterization and annual SCS records. Two-trait genomic models were used for the parameter estimation and GWAS. Results showed significant genetic correlations, and colocalized QTLs for LSCS and nine bacterial operational taxonomic units (OTUs) on chromosomes 3, 17, and 20. We found a genetic association between resistance/susceptibility to mastitis, using LSCS, and the ruminal bacteria abundance. These preliminary results pave the way for better understanding the biological basis and causalities of an intra-mammary inflammations in sheep.