Population structure of dairy cows in Omsk Region by CSN2, CSN3 genes and some genetic anomalies

The aim of the study is to investigate genetic polymorphism of the kappa-casein, beta-casein genes and the main genetic anomalies in a herd of Black-and-White cows bred in the Omsk Region. The object of the study was Black-and-White cows and their fathers; the material of the study was the genotypes of 50 cows, candidates for the leading group of the herd of a breeding reproducer. Of the group of bulls, fa-thers of cows, 54.3 % were carriers of А2 CSN2. The B allele of the CSN3 gene in the structure of the group of cows' fathers was found in 60% of bulls. The genetic structure of cows of the leading group for the CSN2 gene is represented by the А1, А2, А3, В, I, F alleles. The А1 allele has the highest frequency in the popula-tion (45 %), the F allele has the lowest frequency (0.71 %). The share of CSN2А1А2 heterozygotes accounts for 37.14 %. The frequency of occurrence of carriers of the associated allele А2with productivity in the study group was 47.14 %. In the structure of the cow gene pool, the highest specific weight has the allele A of the CSN3 gene, the frequency of occurrence is 62.14 %. The proportion of the B allele was 31.43 %. Allelic variants C, G, H, I, J of the CSN3 gene were not detected. Cows with the CSN2А2А2 genotype exceed individuals with alternative variants of the CSN2. gene in terms of the mass fraction of milk protein by 0.38 % (P < 0.01). Cows with desirable genotypes for the kappa- and beta-casein genes are 49.77 kg or 24 % heavier and 43.30 kg or 21.12 % (P < 0.01) heavier than their peers with the absence of desirable alleles of the studied genes in the genotype, respectively. The recessive allele of the brachyspin anomaly is most widespread in the group – 2.14 %. The recessive allele of the seventh Holstein haplotype and leu-kocyte adhesion deficiency account for 1.43 % each in the genetic structure of the leading group. The ge-netic diversity of the studied part of the herd for the CSN2 and CSN3 genes allows using optimal genotypes in the breeding system and improving the herd in terms of technological characteristics of milk. To exclude the spread of the genetic load in the population, it is important to control the fixation of parental pairs taking into account the carriage of genetic anomalies.