Scientifc studies were conducted in breeding herds of the Ukrainian Brown dairy breed and the Sumy inbred type of the Ukrainian Black-and-White dairy breed to investigate the peculiarities of capa-casein gene polymorphism. What these breeds have in common is their descent from the same autochthonous breed, the Lebedyn breed. The process of creating these breeds was distinguished by the use of sires of different breeds, namely Swiss and Holstein. Genotyping of 60 cows (30 of each breed) was carried out. The polymorphism of the capa-casein gene was determined in the genetic laboratory of the Bogomolets Institute of Physiology of the National Academy of Sciences of Ukraine using molecular biological analysis of allele recognition by real-time polymerase chain reaction (PCR). It was found that Ukrainian brown dairy cows were distinguished by a higher frequency of the desired homozygous BB genotype, it was 40%. A higher frequency of homozygous genotype AA was characterised by cows of Sumy inbred type of Ukrainian Black-andWhite dairy breed (68 %). The proportion of heterozygous genotype AB was higher in cows of the Ukrainian Brown dairy breed (48 %). The frequency of the B allele in animals of the Ukrainian Brown dairy breed was 0.64, while in cows of the Sumy inbred type of the Ukrainian Black-and-White dairy breed it was only 0.20. Correspondingly, a higher frequency of allele A was observed in animals of the Sumy inbred type of the Ukrainian Black-and-White dairy breed (0.80). The ratio of allele frequencies in the animals of the studied breeds was, respectively, 1.8 times and 4 times. The actual proportion of heterozygotes was lower than expected in animals of the Sumy inbred type of the Ukrainian Black-and-White dairy breed. On the contrary, the actual heterozygosity was higher than expected in cows of the Ukrainian Brown dairy breed. The results of the analysis of the breeding data of the sires from which the animals in the experimental farms originated indicate that a small proportion of them were evaluated for the capa-casein genotype. Of the sires evaluated, only 44% of Holstein sires had the BB genotype, while 67% of Swiss sires had the BB genotype. Considering the results of the research, we believe that the formation of herds with the BB genotype is possible in the populations of both studied breeds. In the future, it will be possible to create quickly enough breeding herds with specifed genetic parameters at the request of processing enterprises. For this purpose, it is necessary to use sires that have the BB genotype for the capa-casein gene.
Key words: breed, milk yield, fat content, protein content, capa-casein, genotype, allele.
