Our findings highlight the significance of SNPs in SELL, ABCG2, SLC11A1, FEZL, SOD1, CAT, GPX1, and AhpC/TSA genes as genetic markers and predisposing factors for mastitis tolerance/susceptibility in Holstein and Brown Swiss breeds; these findings suggest that variability in these genes could be used as proxy biomarkers for such disorders in dairy European cattle. The gene discussed is ABCG2; the disease is mastitis.