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The study of polymorphism of beta-casein genes CSN2 and kappa-casein CSN3 in cows of Brown cattle, Simmental breed, Black and White cattle has been carried out with the use of polymerase chain reaction in real time. It is shown that the frequency distribution of CSN2 / CSN3 composite genotypes differs significantly in different breeds: Brown cattle - 22.0 А1А2/AB, 22.7% А2А2/AB and 22.0% А2А2/BB; Simmental - 26.8% А1А2/AB; А2А2/AF, 22.0%, А2А2/AB 19.5%; Black and White cattle - 26.9% А1А2/AA; А1А1/AB, 23.1%, А2А2/AA 23.1%. The obtained results indicate the prospects of breeding work concerning the formation of herds (micropopulations) by the A2A2/BB composite genotype, which is only possible among Brown breeds. This makes it possible to increase the effectiveness of measures to preserve the population of Brown cattle by improving the quality of their milk. [ABSTRACT FROM AUTHOR]

Simple Summary: Milk protein polymorphisms, especially κ-casein and β-lactoglobulin, are essential for the dairy and cheese industries. However, BB CSN3 is a more favorable polymorphism, as it is responsible for a higher casein content. Statistically significant differences (p ≤ 0.05) in interpregnancy periods values were observed between cows with the BB kappa-casein genotype and cows with the AA genotype—the former exhibited the shortest interpregnancy periods. Additionally, cows with the BB genotype showed more favorable reproductive indices, i.e., the lowest age at first calving and the lowest insemination index. However, these values were not statistically significant. There was no significant influence of any of the analyzed kappa-casein and beta-lactoglobulin genotypes on the course of cows' delivery. This research sought to determine the effect of selected milk protein polymorphisms on the reproduction parameters of 598 black and white Polish Holstein–Friesian cattle. The analyzed genes were kappa-casein (CSN3) and beta-lactoglobulin (BLG). The following reproductive indexes were selected: the age at first calving, the interpregnancy period, the calving interval, and the insemination index. The influence of the identified genotypes on the course of parturition in cows was also analyzed. Source data were collected for each cow from the beginning of the herd life and reproduction to its culling from the herd or the end of its third lactation. Data on the age at first calving, the amount of semen portions for artificial insemination (insemination index), the interpregnancy period, and the calving interval for each cow were also collected. A contingency analysis was performed through contingency tables using a Pearson's chi-squared test for each CSN3 and BLG genotype. The results show that the BB genotype of the kappa-casein gene was associated with the most favorable values of reproductive indicators. In the case of the calving interval, the values were significantly more favorable than those of other genotypes (p ≤ 0.05). No effect of beta-lactoglobulin polymorphism on the analyzed reproductive indices was observed. On the other hand, in the case of the interpregnancy period, significant statistical differences were obtained between the AA and BB genotypes. The analyzed kappa-casein and beta-lactoglobulin genotypes did not significantly influence the course of parturition in cows. To conclude, the genotype polymorphism BB CSN3 is the most favorable for the performance of the cows in the examined herd. [ABSTRACT FROM AUTHOR]

Genotyping of 47 stud bulls of Brown breeds was carried out by the gene CSN3. The results of scientific studies indicate that both Brown purebred and cross-breed cattle bred in Ukraine are characterized by a significant difference in the frequency of genotypes by this trait. The genetic equilibrium established by us corresponds to the global trends of breed populations. The creation of the desired micro-populations with the desired homozygous BB genotype by kappa-casein makes it possible to improve the quality of milk as a raw material for milk processing enterprises specialized in cheese making. Therefore, the increased frequency of the BB genotype by kappa-casein may contribute to the preservation and distribution of Brown cattle in Ukrainian farms. [ABSTRACT FROM AUTHOR]