Changes in the genetic structure in the herd of Lebedinian cattle by β-casein genotype

Abstract

The peculiarities of the formation of the genetic structure of β-casein in the herd of Lebedinian breed were studied. The direction of the study is based on the fact that the consumption of milk containing β-casein A1 contributes to the development of human type I diabetes, heart disease, autism, gastrointestinal discomfort and other diseases. For this reason, there is a growing global interest in A2 milk. The research was conducted on the basis of a breeder for breeding Lebedinian breed of the ALC “Komyshanske». Genetic analysis of materials was performed on the basis of the laboratory of the Institute of Animal Husbandry of the National Academy of Agrarian Sciences of Ukraine. Cattle genotypes were determined by allele-specific PCR (AS-PCR). As a result of this work, it was found that the frequency of heterozygous A1A2 genotypes in cows was 38%, homozygous A1A1 - only 5%, and the desired A2A2 - 57%. Respectively, the frequencies of alleles were - A1 - 0.238 and A2 - 0.762. When implementing our proposed method for creating herds of animals with the A2A2 genotype, it was planned to obtain the following distribution of genotypes in the next generation of animals (daughters): A1A2 - 24%, A2A2 - 76%. The use of bulls in the farm, only three of which had the desired genotype A2A2, three - A1A2, and two - were not evaluated on this basis - contributed to the heifers (second generation) frequency of the genotype A1A1 - 0%, A1A2 - 34%, A2A2 - 66%. There was no statistically significant difference between daughters and mothers on this basis. The frequency of alleles was A1 - 0.172 and A2 - 0.828, which did not correspond to the predicted (by 0.052). It was found that the degree of homozygosity in the herd increases from 67.3 in mothers to 71.4 in daughters, the level of polymorphism in the β-casein locus decreases from 1.56 to 1.39, the heterozygosity test in both generations was positive. Data from genetic and statistical analysis indicate an increase in the β -casein locus of heterozygous A1A2 genotypes and a lack of homozygous ones. Based on the results of the research, breeders were offered to conduct genotyping of the entire breeding stock of the herd and use only producers evaluated by β-casein genotype (homozygotes A2A2) for reproduction. In order to accelerate the creation of a herd of animals with A2A2 genotypes by β-casein - we propose to use isolated by gender sperm of bulls-producers with this genotype.