The aim of this paper was to evaluate the effect of genetic polymorphism of kappa-casein on milk production in Holstein cattle. Two hundred and ten Holstein cows were used in this study. We established genotype structure of cattle population and calculated allelic frequencies based on PCR-RFLP analyses. The three genotypes: AA (69.52%), AB (27.62%), and BB (2.86%) were detected. Frequency of allele A was 83.33%, and of allele B 16.67%. The Holstein cattle kept in Slovak Republic exhibit a high value of homozygosity (0.7222) and low values of polymorphism information content (0.2392), effective number of alleles (1.3847) and level of possible variability realization (27.91%). The effect of polymorphism of CSN3 gene on average breeding values for milk production traits, such as yield of milk, fat and protein expressed in kilograms, as well as percentage content of fat and protein in milk, has been assessed. In our assessment of the observed traits' variability's dependence on CSN3 gene polymorphism, we detected a statistically significant difference between genotypes only in case of the average breeding value for the percentage of protein in milk.
Keywords: CSN3; Holstein cattle; genetic structure; kappa-casein; milk production.