Distribution of beta-casein genotype in two generations in cows of the Kholmogory breed

Abstract

One of the most effective ways to produce A2 milk is marker selection using the results of animal genotyping according to beta-casein genotypes, since A2 milk is produced only by cows with the A2A2 genotype. In this study, the inheritance of the beta-casein gene genotype in two generations of cows of the Kholmogory breed in "Agrofirma "Kholmogorskaya" and "Kholmogorskiy plemzavod", Arkhangelsk region was studied. The A1 and A2 alleles of the beta-casein gene were determined by an allele-specific PCR method. As a result of the study, it was found out that the frequency of the A1 and A2 alleles of the beta-casein gene in daughter offspring and mother cows practically did not change in one generation (A1 allele from 53 to 54 % and A2 allele from 46 % to 47 %; A1 allele from 68 to 61 % and A2 allele from 32 to 39 %). This fact indicates the absence of breeding pressure. Since the task of modern animal husbandry is to create herds of the Kholmogory breed with the A2A2 genotype for the production of high-quality milk, then for further breeding, attention should be paid to animals with the A1A2 and A2A2 genotypes. Having modeled the selection in herds, that is, excluding mothers with the A1A1 genotype from reproduction, and calculating the distribution of genotypes of descendants in the remaining part of the maternal stock of both herds, it was found that the proportion of descendants with the A1A1 genotype decreases in farms, the relative number of heterozygous daughters in the breeding farm increased by 5.0 %, and in the agrofirm decreased by 6.3 %, but at the same time, the number of A2A2 daughters increased by 6.7 and 4.0 %, respectively.