The role of kappa-casein (CSN3), beta-casein (CSN2), betalactoglobulin (BLG) and alpha-lactalbumin (LALBA) genes in the formation of milk productivity of black-and-white cows

The article presents the results of a study about polymorphism of casein (CSN2, CSN3) and serum (LALBA, BLG) protein genes and an assessment of their impact on milk productivity of black-and-white cows in the Republic of Bashkortostan. The experimental part of the work was carried out on a sample of 235 black-and-white cows in the second lactation in Kalinin Agricultural Company of Sterlitamak District in 2020-2023. The methodology of the study included molecular genetic analysis by PCR-RFLP followed by electrophoretic detection of restriction fragments in 7.5% polyacrylamide gel. As a result of genotyping, the dominant genotypes were identified: CSN2 A1A1 (71±0.03%), CSN3 AA (87±0.03%), LALBA AB (58±0.03%), LGB AA (58±0.02%). The homozygosity levels for the studied loci were established: CSN2 - 73%, CSN3 - 87%, LALBA - 56%, LGB - 60%. Genetic equilibrium analysis revealed statistically significant deviations from Hardy-Weinberg equilibrium at the LALBA (Selender coefficient +0.32, χ2=26.02) and LGB (Selender coefficient -0.25, χ2=13.48) loci. A comprehensive assessment of milk productivity revealed that the maximum milk yield of 5872.57±184.15 kg was typical for animals with CSN2 A2A2 genotype. In cows with CSN3 AB genotype, the milk yield was 5793.47±109.85 kg and the protein mass fraction was 3.29±0.04%. In cows with LALBA BB genotype, the milk yield was 5991.66±140.89 kg and the protein yield was 195.33±14.23 kg. In cows with LGB AA genotype, the maximum protein mass fraction of 3.30±0.04% was revealed. The obtained results indicate the need to develop innovative selection and genetic programs that take into account the identified genetic features of the population to optimize quantitative and qualitative indicators of milk productivity.