Genetic Polymorphisms at the K-casein locus in Russian breeds Black- pied and Drojba cattle

Casein is a family of milk proteins that exist in several molecular forms and are the main proteins present in the bovine milk. The B variant of bovine k-casein is reported to be favorable for milk quality and quantity of cheese derived from milk and considered to be included in breeding strategies of dairy cattle. Genotypes of 72 Russian Black pied and 80 Drojba cows were determined for kappa casein locus by restriction fragment length polymorphism analysis (PCR-RFLP) of amplified DNA. A 530 b.p. fragment of the genomic bovine kappa casein gene was amplified by PCR. Digests by Hind III thus genotypes AA, AB and BB, were recognized by agarose gel electrophoresis 3% and ethidium - bromide staining. This technique was used to determine the kappa casein allelic frequency in Black pied and Drojba dairy herds. Estimated gene frequencies were 0.83, 0.69 for the A and 0.17, 0.31 for the B alleles, for Black pied and Drojba breeds, respectively, with observed heterozygosis of 0.28, 0.50 for Black pied and Drojba breeds, respectively. This molecular genetic technique based on molecular markers allows direct genotyping for milk Kappa casein with certainty and accuracy in bulls and females to be used in programs of dairy cattle improvement. Therefore, an early and precise identification of milk protein genotypes should have a direct impact on dairy cattle breeding strategies.