By PCR-DNA sequencing of the RASGRP1, NFkB, CHL1, MARCH3, PDGFD, MAST3, EPS15L1, C1QTNF3, CD46, COX18, NEURL1, PPIE, and PTX3 genes, single nucleotide polymorphisms (SNPs) associated with mastitis resistance/susceptibility were found between mastitis healthy and affected Holstein and Montbéliarde. The gene discussed is COX18; the disease is mastitis.