effect of k -casein genotypes on milk yield in second-generation dairy cattle

Improving the qualitative and quantitative characteristics of milk is crucial for national food safety. Genetic marker selection demonstrates good prospects in this regard, the most promising genetic marker being k-casein, or kappa-casein. The AB and BB genotypes of k-casein are associated with such positive milk properties as high protein content, good coagulation, and increased yield of cottage cheese or cheese. The research objective was to identify inheritance patterns in female calves obtained from cows with various genetic backgrounds. These results were checked for correlation with milk yield indicators. The experiment featured cows of the Kholmogorsky breed and their female calves. It was conducted in 2023 on the premises of two breeding farms, i.e., Kholmogorskaya Plemzavod and Kholmogorskaya Agrofirma. The DNA was isolated using a set of MagnoPrime VET reagents. The polymorphism test of the k-casein gene was performed by the RELF PCR method. The experiment revealed the frequency of occurrence of genotypes and alleles of the k-casein gene. In both farms, A allele was more frequent in both mother cows and calves than the B allele. The AA genotype predominated in both generations. In Kholmogorskaya Plemzavod, the highest milk yield (6,741 kg) belonged to the calves with a homozygous genotype for allele A, which they received from their mothers with a heterozygous genotype. A similar trend (6,008 kg) was established in calves with a homozygous genotype for allele B, which they inherited from their mothers with a heterozygous genotype AB. In Kholmogorskaya Agrofirma, the highest milk yield (7,592 kg) was observed in the second-generation cows with a homozygous BB genotype, which they received from their mothers with a heterozygous AB genotype.