Aim. To investigate the genetic structure of populations of the Ukrainian Red-and-White Dairy cattle (URW) and its crossbreeds based on SNP g.10153G>A at SCD1 locus and to evaluate the association of this polymorphism with traits of dairy performance and the fat and protein content in milk. Methods. The genetic structure of two groups of cows (purebred URW, n=43; URM × M crossbreeds, n=41) was studied by g.10153G>A polymorphism of SCD1 gene using the PCR-RFLP method. The performance was assessed using the indicators from the first completed lactation. The correspondence of the distribution of quantitative traits to the normal law was tested using the Shapiro-Wilk test. For normally distributed traits (milk yield), one-way analysis of variance (ANOVA) with Tukey's post-hoc test was used; for non-normally distributed traits (fat and protein content), the Kruskal-Wallis test with Dunn's post-hoc test adjusted for Bonferroni correction was used. Results. Certain intergroup differences in allele distribution were observed: in purebred animals, a slight predominance of allele G was observed (0.535 versus 0.465 for allele A), whereas in crossbreeds, a relative increase in the frequency of allele A was noted (0.524 versus 0.476 for allele G). In the crossbreed group, an increased frequency of the heterozygous AG genotype (0.512) was also observed. For milk yield indicators, opposite genotype-associated trends were identified between groups: in purebred animals, the highest mean values were observed in homozygous AA individuals, whereas in crossbreed animals, they were observed in heterozygous AG individuals; however, within individual groups, no statistically significant differences between genotypes were found (p > 0.05). No statistically significant associations with genotype were found for fat and protein content (p > 0.05). Conclusions. The results obtained indicate the presence of certain genetic differentiation between the study groups at the SCD1 locus and a possible dependence of the manifestations of the associations on the genetic background of the population. At the same time, no statistically confirmed effects of polymorphism on milk yield, fat content, or protein content were found. Further studies using larger sample sizes are needed to clarify the nature of the identified trends.
