In this study, the frequency of the SOCS2 SNP allele was found to decrease for AI rams (from 0.21 in 2005 to 0.09 in 2017), which might be explained by the introduction of the SCS trait, considered as a proxy for mastitis, into the breeding objectives in Lacaune dairy sheep in 2005 [28, 29]. This evidence concerns the gene SOCS2 and mastitis.