The genotypes for kappa-casein locus were established using PCR-RFLP. Genome DNA for PCR amplification was isolated from hair roots in cows (30 Schwitz individuals), and from frozen semen in bulls (42 bulls of different breeds). A higher frequency of the B allele in Schwitz (pA = 0.45 and qB = 0.55 in cows and pA = 0.25 and qB = 0.75 in bull
...s), and a higher frequency of the A allele in bulls belonging to different breeds (pA = 0.61 and qB = 0.39 in Deutsch Simmental, pA = 0.84 and qB = 0.16 in Romanian Simmental; pA = 1.00 and qB = 0.00 in Holstein, and pA = 0.67 and qB = 0.33 in Pinzgauer) were estimated. The associations between the genotypes and alleles determined at the kappa-casein locus and milk production were tested. They emphasized significant associations only for milk and milk fat quantity, in advantage of individual carriers of the B allele in homozygous and heterozygous states.