INFLUENCE OF BETA-CASEIN GENOTYPE ON MILK QUALITY INDICATORS IN BROWN CATTLE

Abstract

In breeding herds of Lebedinian and Ukrainian brown dairy breeds, studies were conducted to study the polymorphism of the beta-casein gene and its effect on the quality of cow's milk. Genotyping of 242 head of cattle of the above breeds was carried out. Determination of beta-casein gene polymorphism was performed in the genetic laboratory of the Bogomoletz Institute of Physiology. The TagMan@Genotyping system and a set of primers and probes were used for allelic discrimination. It was found that the fre-quencies of alleles A1 (0.308-0.313) and A2 (0.687-0.692) in the locus of the beta-casein gene in animals of different breeds dif-fered. The population of Lebedinian cows had the highest frequency of the desired A2 allele (0.692), and the Ukrainian brown dairy population had the lowest frequency (0.687). The frequency of the A1 allele was the lowest in cows of Lebedinian breed (0.308) and the highest - in cows of Ukrainian brown dairy breed (0.313). Accordingly, the frequencies of genotypes A1A1, A1A2 and A2A2 dif-fered depending on the origin. The desired genotype was more common in animals of Lebedinian breed (51%). Heterozygous geno-type was more characteristic of animals of the Ukrainian brown dairy breed (45%). The highest frequency of the A1A1 genotype was characterized by Lebedinian animals (13%). According to genetic and statistical analysis, an excess of homozygous variants of A1A1 and A2A2 in the beta-casein locus was found. Heterozygous A1A2 deficiency was found in animals of Lebedinian breed. There was a difference in the quality of milk between animals of different genotypes. In animals of different breeds, the content of individual components of milk did not vary equally depending on the genotype of beta-casein, but this difference was statistically insignificant. In terms of fat and protein content in milk, animals of all genotypes met the breed standard. Thus, it can be stated that the formation of herds with the A2A2 genotype for beta-casein will not have a negative impact on the productive traits of cows and thus ensure the preservation of high quality of milk of cattle herds of a new type. The small number of experimental animals, in our opinion, was one of the reasons for the lack of a significant difference between the average values of the milk components of cows of different geno-types for beta-casein.