Results of the Ayrshire breed cows, Holstein cows and Holstein-Yaroslavl cross breed cows milk productiv-ity analysis in the same environment conditions and depending on the kappa-casein and beta-lactoglobulin genotypes are presented in this article. The animals are kept in the common environmental conditions of the LLC Farming firm “Pakhma», the Ayrshire breeding plant. Feeding of cows here is carried out according to detailed norms, concentrated feed averages 43%. The maintenance system is year-round stalling, milking is carried out in the milk line, the DeLaval milking machine is used, and labor-intensive processes in animal husbandry are mechanized. The farm has a milk processing shop. It was established that all the inspected cows (n=91) had a prevailing AA kappa-casein genotype – 75,8% on average. BB Ayrshire breed and Hol-stein-Yaroslavl cross breed genotypes were not established. AB and BB beta-lactoglobulin genotypes are seen on average with a frequency of 44%. AA beta-lactoglobulin genotype in Holstein cows breed was not found. The indicators of statistically reliable difference in milkability among all groups and genotypes was not estab-lished. A higher consistence of protein in the milk of B-allele kappa-casein type cows is evident in all groups with no difference between breed belonging. The complex variant of CSN3/LGB genotypes showed that ac-cording to ultimate milk fat and protein yield the most productive cows were:АВ/ВВ, АВ/АВ genotype Ayr-shire cows, АВ/АВ Holstein genotype cows, AB/BB genotype Holstein-Yaroslavl cross breed cows. Hence, the most efficient cows are those with B-allele variants.