Polymorphism of the kappa-casein gene and its relationship with milk productivity and milk quality of cows of different linear origin

Abstract

Background. The efficiency of dairy farming is largely determined by the increase in cow productivity and depends on the quality of milk, which has significantly deteriorated in recent years. Materials and Methods. Genomic DNA was extracted from individual samples of biological material (hair samples with bulbs) taken from cows using a commercial set of reagents “DNA Sorb B” (AmpliSens). Polymerase chain reaction was performed on an Amply-4-2 amplifier (Biokom); detection was performed using a UVD transilluminator (Biokom). Milk productivity was recorded according to the results of individual monthly control milkings of cows. Results. Genetic analysis has proven the polymorphism of the kappa-casein locus in the experimental array of cows of the Ukrainian Black-and-White dairy breed, represented by three genotypes: AA (63.1 %), AB (31.6 %), BB (5.3 %), with a predominance of the frequency of the A allele (0.79). Cows with the AA genotype of the Starbuck line demonstrate maximum milk productivity, surpassing animals with the AB genotype by 361.6 kg or 5.8 % against the background of a probably significant advantage over representatives with the BB genotype – by 727.6 kg or 12.3 % (p < 0.01). At the same time, individuals with the AB genotype of the Chifa line in terms of milk yield per lactation exceeded animals with the AA genotype by only 25.8 kg or 0.4 %, while in the group of cows with the AB genotype of the Valiant line, the difference in the corresponding indicator, on the contrary, was lower compared to animals with the AA genotype of the same line by 559.0 kg or 9.2 %. During laboratory analysis, it was found that cows with the BB genotype of the Starbuck and Elevation lines had higher values of the mass fraction of fat in milk by 0.01 and 0.20 %, compared to animals with the AB and AA genotypes of the Starbuck line and by 0.09 and 0.18 % in the Elevation line. These animals are also characterized by higher values of the mass fraction of protein by 0.39 and 0.25 %, and 0.45 and 0.49 %. Conclusion. The results of the research indicate the polymorphism of the experimental array of cows of the Ukrainian Black-and-White dairy breed, which is represented by three genotype: AA (63.1 %), AB (31.6 %), and BB (5.3 %), with the prevalence of the frequency of the A allele (0.79). Cows-descendants with the AA genotype of the Starbuck line are characterized by a higher milk yield by 5.8 and 12.3 % than animals with the AB and BB genotypes, while cows with the BB genotype of the Elevation line have a higher content of mass fractions of protein by 0.42 and 0.49 % and fat by 0.18 and 0.09 % compared to animals with the AA and AB genotypes.