Monitoring the highest breeding groups of Kholmogor cows

Abstract

This article presents the results of monitoring the highest breeding groups of Kholmogor cows for the frequency of the κ-casein and β-lactoglobulin genotypes in 2010–2013. In 2010, the κ-casein genotypes AA and AB were detected, respectively, in 70% and 28% of cows, while less than 2% of cows had the genotype BB and the A and B alleles were met at the frequencies of 0.84 and 0.16, respectively. The frequency of the B allele increased in 2013 to 0.20 against a decrease in the frequency of the AA genotype to 66% and the increased frequency of the BB genotype to 5%. Nearly half of the cows in 2010 had the β-lactoglobulin BB genotype (46%). The genotypes AB and AA were met at a frequency of 26–28%. The frequencies of the A and B alleles accounted, respectively, for 0.4 and 0.6. The frequency of β-lactoglobulin alleles remained unchanged in 2013. The frequency of the AB genotype increased from 28% to 45% against a decrease in the frequency of homozygous genotypes AA and BB up to 17% and 38%, respectively. We have revealed eight complex κ-casein/β-lactoglobulin genotypes. In 2010, the frequencies of the genotypes accounted 31% for AA/BB, 21% for AA/AB, 18% for AA/AA, 16% for AB/BB, 8% for AB/AB, 5% for AB/AA, and less than 1% for the BB/AB and BB/BB genotypes. The genotype BB/AA remained unfound. In 2013, the distribution of the genotypes changed. The AA/AB and AA/BB genotypes reached 30% and 24%, respectively, while the AB/AB genotype was met in 15%. The frequencies of the AA/AA, AB/BB, AB/AA, BB/BB, and BB/AB genotypes accounted for 12%, 10%, 5%, 3%, and 2%, respectively. Therefore, the percentage of cows with the homozygous AA/AA genotype that is undesirable by its technological traits of milk has shrunk from 18% to 12%.