The general population-genetics parameters of Ukrainian black-and-white and red-and-white dairy breeds are studied, the microevolutionary processes specifications are revealed. A studies of genetic structure characteristics of experimental populations by prolactin gene (PRL), placental lactogen gene (PL), growth hormone receptor gene (GHR), leptin gene (LEP), tumor necrosis factor alpha gene (TNF-α) and myogenic growth factor 5 gene (MYF5) were carried out. The results showed that the PRL, GHR, LEP, MYF5 and TNF-α genes were polymorphic in both experimental cow populations. The deviation from Hardy-Weinberg genetic equilibrium state in the red-and-white dairy cow population was detected. The presence of different allelic variants for leptin locus (HphI-рolymorphism in the third exon, mutation A59V) was founded. In the population of black-and-white dairy cows, the frequency of the C allele was 0.77; allele T – 0.23; in the population of red-and-white dairy cows – 0.72 and 0.28, respectively. In the population of cows of
black-and-white dairy breed deviations from Hardy-Weinberg genetic equilibrium state was detected. By TaqI-polymorphism in the second intron of the myogenic growth factor 5 gene, the frequency of the TaqI + allele was 0.65; TaqI- allele – 0.35 in the population
of black-and-white dairy breed and 0.64 and 0.36 in the population of red-and-white dairy breed, respectively. Both cow populations were in a genetic equilibrium state. The polymorphism of the fragment of tumor necrosis factor-alpha gene was studied. 6 alleles, 450-1200 bp in size, were identified – alleles A, B and F in the population of black-and-white dairy breed; A, B, C, D, E, F – in the population of red-and-white cows. In both cases, a significant predominance of allele frequency A (0.58 and 0.54) was detected. It should be noted that the only one type of homozygous individuals, belongs to the genotype AA, were found in both cattle breeds. All addition allelic variants were presented in the form of heterozygous individuals. the Ukrainian red-and-white breed shows a much higher level of polymorphism of the TNF-α locus by number of detected alleles and genotypes. It have shown that different populations of Ukrainian black-and-white dairy cows were characterized by a predominance of «dominant» alleles by PRL, LEP and TNF-α loci. According to the results of the analysis, the following regularities were established: monomorphic character of the PL locus in both experimental populations; the prevalence of «dominant alleles» at different loci (allele C frequency over T by PRL, allele C frequency over T by LEP, allele A frequency over B and F by TNF-α) in both groups of animals; pronounced differences in the values of
the frequencies of different genotypes at each of the loci; significant differences in parameters of actual and expected heterozygosity (respectively in the level of genetic variability of populations); significant differences in the value of the Wright fixation index. In the absence of the use of targeted selection by genotype (MAS, genomic selection) populations differ by individual loci due to differences in the original breeding material, as well as the possible influence of microevolutionary factors such as gene selection and genetic drift. According to the results of the study it was founded that the increased values of the milk yield for 305 days were characterize individuals with opposite homozygous genotypes by the prolactin locus for different cattle populations. For the Ukrainian black-and-white dairy breed the desirable genotype was CC, for the Ukrainian redand-white dairy breed – the TT genotype. Аt the growth hormone receptor gene, the predominant values of the fat content of milk for homozygous individuals by AluI+ allele for Ukrainian black-andwhite cows were recorded. For leptin locus, it was found that homozygous individuals by C allele are characterized by higher values of the milk yield for 305 lactation days for both experimental cattle breeds. For the population of the Ukrainian black-and-white dairy breed, the most perspective functional units for research and use in breeding programs were prolactin gene (RsaI-polymorphism in the fifth exon), leptin gene (HphI-polymorphism in the third exon), growth hormone receptor gene (AluI-polymorphism of the promoter fragment) and myogenic factor 5 gene (TaqI-polymorphism in the second intron). For this breed, the formula of the desired genotypes in the direction of increasing the value of milk yield for 305 lactation days – PRL^CC LEP^CC MYF5^TaqI+/TaqI-; in the direction of increasing the milk fat content – GHR^AluI+/AluI+ LEP^TT. Prolactin and leptin loci are the most perspective for the population of the Ukrainian red-and-white dairy breed. For this breed, the formula of the desired genotypes in the direction of increasing the value of milk yield for 305 lactation days – PRL^TT LEP^CC; in the direction of increasing the milk fat content – LEP^CT.
