Genetic analysis of the Montbeliard breed for the suitability of A2 milk use in food technologies

Background. Cow milk has long been a source of protein and certain micronutrients, such as calcium. A2 milk is gaining popularity among consumers who are constantly looking for healthy foods. One factor that affects the quality of milk proteins is the breed of cattle. Over the last decade, countries such as the USA, the EU, India, China, and others have been widely assessing the frequency of β-casein genotypes in dairy cattle of various breeds. Research has shown that the desirable A2 allele of milk β-casein exhibits a broad occurrence range across countries and breeds, varying from 24 to 80.9 %. The aim of this study was to conduct a genetic and biochemical assessment of the Montbeliarde breed to determine its suitability for the use of A2 milk in food technologies. Materials and Methods. The polymorphism of the CSN2 gene was investigated by the ACRS-PCR method following the McLachlan protocol. The frequencies of alleles and genotypes of the CSN2 gene (β-casein) in the Montbeliard breed of cattle were determined. The DdeI restriction enzyme was used. The physicochemical parameters of milk were determined through conventional methods. Results. According to the physical and chemical parameters, the milk of Montbeliard cows meets the standards of this breed, namely the ratio between fat and protein in milk is about 1.2:1, which is the norm, the average lactose content in milk was 5.23 %, and the average protein content was 3.35 %. An analysis of β-casein gene polymorphism in Montbeliarde cows revealed that 27 % of the animals carried the homozygous CSN2A1A1 genotype, 56 % had the CSN2A1A2 genotype, and 17 % possessed the “desi­rable” homozygous CSN2A2A2 genotype for obtaining A2-milk. Conclusions. Among the Montbeliarde cows studied at LLC “Inter” in the Chernihiv Region, 17% of the tested cows carried this genotype, making them suitable for producing milk free from the “harmful” A1 β-casein. It has been confirmed that A2 milk is obtained from cows carrying the CSN2A2A2 β-casein (CSN2) genotype. In terms of all biochemical parameters, the herd with the A2A2 β-casein genotype demonstrated high-quality milk characteristics. In terms of protein content, there is almost no difference between the groups by homozygous genotype, while the fat content in cows with the homozygous genotype CSN2A2A2 is higher by 0.78 % compared to the homozygous genotype CSN2A1A1 and 0.62 % – CSN2A1A2.