Analysis of dairy productivity of cows of ukrainian brown dairy breed of different genotypes by kappa-casein

Abstract

In the herd of cattle of the Ukrainian Brown Dairy breed studies were conducted, the purpose of which was to study the influence of the genotype of cows by kappa-casein on the indicators of their milk productivity. Genotyping of 29 heads of cattle. Determination of the polymorphism of the kappa-casein gene was performed in the genetic laboratory of the Institute of Physiology n.a. Bogomolets of NAS using molecular biological analysis of allele recognition by polymerase chain reaction (PCR) in real time. Allele A had a slightly higher frequency - 0.517 compared to allele B - 0.483 at the locus of the kappa-casein gene, although it was not significant. As a result, the proportions of AA and BB genotypes were high (38 and 34%, respectively). The performed genetic-statistical analysis revealed an excess in the kappa-casein locus of homozygous variants AA and BB and a lack of heterozygous AB. The degree of homozygosity, which is 50.1%, indicates a sufficient level of consolidation in the studied population of cattle. The number of effective active alleles in the kappa-casein locus of cows of the Ukrainian Brown Dairy breed is 1.99, with the maximum value of the level of polymorphism possible at a two-allele locus of 2. A negative heterozygosity test (HT) indicates a lower proportion of actual heterozygotes relative to the proportion of theoretical heterozygotes. The reason for the existing genetic structure of the herd of Ukrainian Brown Dairy breeds by the kappa-casein locus was the use of Swiss cattle breeders, most of which were not evaluated by the genotype of the kappa-casein gene. Studies of the level of milk productivity of cows of different genotypes by kappa-casein in the first lactation did not reveal a significant difference. At the same time, heterozygous (AB) animals were inferior to homozygous (AA and BB) in terms of milk yield, and animals with AA and AB genotypes were preferred in terms of quality. For the best lactation, a significant difference was found in the amount of milk yield and the amount of milk fat. Homozygous animals (AA and BB) significantly (p <0.05) outperformed heterozygous (AB) in milk yield, by 1091 and 922 kg, respectively. Animals with heterozygous AB genotype in terms of the average amount of milk fat were significantly inferior to homozygous AA and BB animals (p <0.05). The small number of experimental animals was one of the reasons for the discrepancy between the results of research and the data of other scientists. Key words: breed, milk yield, fat content, protein content, kappa casein, genotype, allele.