Genetic variants of beta-casein in Holstein dairy cattle in Slovakia

Abstract

The aim of the study was to detect allelic and genotypic frequencies of A variants of beta- casein (CSN2) in Holstein cows and bulls in Slovakia and to analyze milk production traits of tested cows in dependence on their CSN2 genotypes. Totally, 92 cows at the first parity and 5 bulls were tested. The samples were taken from cow’s vaginal smear and bull’s semen. DNA analyses were performed using ACRS-PCR (artificially created restriction site – polymerase chain reaction) method. Frequencies of A1 and A2 allele of CSN2 in cows were 0.54 and 0.46. Frequencies of A1 and A2 allele of CSN2 in bulls were 0.60 and 0.40. CSN2 genotypes and their frequencies in cows were A1A1 (0.13), A1A2 (0.83), A2A2 (0.04). Only A1A1 and A1A2 genotypes with frequencies 0.20 and 0.80 were found in bulls. High proportion of heterozygote individuals and genetic disequilibrium were recorded. In the tested cows, least square means for milk yield, protein and fat content (%) were - 8430.8±560.71; 3.17±0.0517 and 3.77±0.167 for the A1A1 genotype, 8434.9±222.80; 3.20±0.020 and 3.90±0.066 for the A1A2 genotype, and 7902.3±971.17; 3.28±0.089 and 3.90±0.288 for the A2A2 genotype. No significant differences in milk traits among CSN2 genotypes of Holstein cows were found.