This paper presents the results on the study of melanocortin-4 receptor (MC4R) gene polymorphisms in sheep of the Karachai breed. AA, AG, and GG genotypes were determined to have allele frequencies of 47%, 37%, and 16%, respectively, indicating that allele A and the homozygous AA genotype occurred the most frequently. Analysis of the meat productivity of sheep, with respect to the MC4R genotype, showed a higher slaughter yield in sheep with the AA genotype compared to those with either the GG or AG genotypes. The variability at these loci provides a basis for controlling the meat productivity of sheep in the Karachai sheep population; therefore, this polymorphism should be monitored and melanocortin-4 receptor (MC4R) gene selection considered in pedigree farms.

Aim. The study of the genetic structure of sheep of the Volgograd and Edilbaevsky breeds according to the GDF9, GH genes. Materials and Methods. The research was carried out in herds of sheep from leading breeding plants, on the basis of Don State Agrarian University and Volga Region Research Institute of Manufacture and Processing of Meat-and-Milk Production. Biosamples of skin and cartilage tissue from the auricles were taken from sheep by plucking an area of 1 cm² for molecular genetic studies. Evaluation was performed by PCR-RFLP method. Endonucleases BstHH HaeIII were used to restrict the amplified regions of the GDF9 and GH genes. The presence and frequency of alleles and genotypes for the GDF9, GH genes were determined based on the results of a molecular genetic study. Results. The article is devoted to the study of the genetic structure of sheep of the Volgograd and Edilbaevsky breeds. One of the important resources for creating highly productive animals is the use of marker selection as an additional criterion for the selection and selection of breeding animals. The use of DNA markers for the selection of animals containing desirable alleles of genes of economically valuable traits is one of the new scientific approaches to solve this problem. The development of sheep breeding in our country will allow using the available natural and human resources in rural areas, as well as obtaining high-quality lamb through the use of resource-saving technologies. The aim of the work was to study the genetic structure of sheep of the Volgograd and Edilbaevsky breeds according to the GDF9, GH genes. To perform molecular genetic studies, samples of ear plucks (tissue from the auricle) with an area of 1 cm2 were taken from sheep. The assessment was carried out by PCR-PDRF. In all the studied groups of sheep, A and B allelic variants of the GDF9 gene, alleles A and B of the GH gene were established. The analysis of the data revealed a breed aspect in the distribution of the frequency of alleles and genotypes of the GDF9, GH genes in the populations under consideration. Conclusion. The results of the study of the genetic structure of the populations of sheep of the Volgograd and Edilbaevsky breeds showed that the frequency distribution of alleles and genotypes of the growth hormone (GH) and differential growth factor (GDF9) genes have some features associated with the breed affiliation of the studied sheep.

The scientific publication presents the results of studies of CAST polymorphism in sheep of the Volgograd breed. Against the background of the limited application of the results of genetic studies when working with the Volgograd breed, the search for polymorphic variants of the calpastatin gene, which is a potential marker of meat quality during maturation after slaughter, and also, according to some data, the live weight of sheep, is an urgent task. Calpastatin is an enzyme belonging to the calpain family of enzymes. CAST gene polymorphism was determined by PCR-RFLP analysis. To carry out molecular genetic studies in sheep of the Volgograd breed (n = 131), tissue samples were taken from the auricle with an area of 1 cm² (ear pinches). In sheep of the Volgograd breed, the presence of two genotypes MM, MN was established with a frequency of 88 and 12%, respectively. The M allele and the homozygous MM genotype had the highest frequency. The analysis of the materials obtained as a result of the control slaughter shows that the Volgograd sheep of the MN/CAST genotype exceeded their peers with the MM/CAST genotypes by 3.7 kg in pre-slaughter weight. The presence of variability at these loci provides a basis for controlling meat productivity in sheep of the Volgograd sheep population, therefore, in breeding farms, monitoring of polymorphism and selection for the calpastatin gene should be carried out.

The aim of this study was to identify genetic variants and pathways associated with the total number of piglets born and to investigate the potential negative consequences of the intensive selection for reproductive traits, particularly the formation of bumps on the legs of pigs. We used genome-wide association analysis and methods for identifying selection signatures. As a result, 47 SNPs were identified, localized in genes that play a significant role during sow pregnancy. These genes are involved in follicle growth and development (SGC), early embryonic development (CCDC3, LRRC8C, LRFN3, TNFRSF19), endometrial receptivity and implantation (NEBL), placentation, and embryonic development (ESRRG, GHRHR, TUSC3, NBAS). Several genes are associated with disorders of the nervous system and brain development (BCL11B, CDNF, ULK4, CC2D2A, KCNK2). Additionally, six SNPs are associated with the formation of bumps on the legs of pigs. These variants include intronic variants in the CCDC3, ULK4, and MINDY4 genes, as well as intergenic variants, regulatory region variants, and variants in the exons of non-coding transcripts. The results suggest important biological pathways and genetic variants associated with sow fertility and highlight the potential negative impacts on the health and physical condition of pigs.