Polymorphism of the genes associated with the formation of productive traits of animals is studied in order to increase the breeding efficiency. The article presents the results of DNA genotyping and live weight indices of replacements of the Dagestan mountain sheep in the age dynamics. The animals carrying the desirable breeding-relevant allele GHB and having heterozygous genotype GHAB surpassed their peers carrying homozygous genotype GHAA in live weight by 2.9 % at the age of 2 months, by 3.5 % at the age of 4 months, and by 5.4 % at the age of 8 months. The index of live weight of the animals carrying the desirable breeding-relevant allele GDF9A with heterozygous genotype GDF9AG and homozygous genotype GDF9AA was several times higher than the one of their peers carrying homozygous genotype GDF9GG; they differed by 5.0 and 10.1% at the age of 2 months, by 2.0 and 5.7% at the age of 4 months, and by 2.4 and 6.1% at the age of 8 months, respectively. The study revealed complex genotypes with the allelic profile represented by one (GHAAGDF9AG), two (GHAAGDF9AA), and three (GHABGDF9AA) selection-relevant marker alleles. It was noted that greater values of live weight were in the animals carrying complex genotypes GHAAGDF9AA, GHAAGDF9AG and GHABGDF9AA, amounting to 14.8, 14.5, 15.3 kg at the age of 2 months, 26.4, 26.2 and 26.9 kg at the age of 4 months, and 33.6, 33.8 and 34.9 kg at the age of 8 months, respectively, against the peers carrying complex genotype GHAAGDF9GG, amounting to 14.3, 25.8 and 32.8 kg, respectively.

The article presents the results of DNA genotyping of sheep of different breeds. It is the first time polymorphism of genes GH-HaeIII and CAST-MspI of replacement sheep of different breeds has been studied and analyzed. The testing results identified specific features of the allele spectrum of the studied genes associated with meat production, expressed in different frequencies of occurrence of both genotypes and alleles. Carrier animals with desirable alleles for breeding were identified in the gene loci under study. Genetic and statistical analysis allows to conclude that the specific weight in the studied populations of sheep of different breeds of particularly valuable genotypes is relatively low. In order to accumulate selection-significant genetic markers in the breeding herds of sheep of different breeds, bred under conditions of the Stavropol Krai and the Republic of Dagestan, regular screening will create conditions for identifying desirable alleles and genotypes, as well as their wide inclusion in the breeding process.

Line breeding is often used in purebred animal husbandry, although the combination of lines may affect undesirable result. Therefore, it is very important for animal breeders to know which lines of animals can be combined to produce highly productive offspring with high meat and wool properties. This article studies the influence of interline selection of Russian meat merino breed on wool productivity, quality and skin histostructure. We found that the highest clipping was in the animals of group III obtained from ME-50 line rams and AS-30 line ewes. Ewes exceeded their peers of group II from the intraline AC-30 selection and peers of group IV from AS-30 line rams and ME-50 line queens. At the same time, ewes of group III insignificantly exceeded peers of group I from intraline selection of ME-50 line animals by 2.0% (P>0.05). Animals of group III had rather high fleece indices in terms of the wool condition due to the influence of ME-50 rams. Moreover, they had the highest ratio of “fat:sweat” (0.84), which confirms the high technological wool properties of this genotype. The quality of sheepskins depends on the nature of the connection of collagen fibers in the reticular layer. In terms of the thickness of the skin reticular layer young ewes of the group III exceeded their peers in groups I, II and IV by 5.3% (P> 0.05), 21.9% ( P<0.01) and 12.0% (P<0.05) respectively.

This article presents the results of a study on the search and development of the most optimal breed for beef production and growing technology using fattening and fattening in the conditions of the Karachay-Cherkess Republic. An experiment was conducted at Hammer LLC, the object of which was the bulls of the Aberdeen-Angus, Swiss and Kalmyk breeds bred in the region. From birth to 18 months of age, bull-calves of all breeds were distinguished by high payment for feed by increments. They spent 5.4-6 feed units per kilogram of growth. The feed fed to one bull for 18 months of rearing contained 2918-3235 feed. units and 295-325 kg of digestible protein. Live weight at the age of 18 months in bulls of the Aberdeen-Angus breed was 589.4 kg, which is more by 28.4 and 68.4 kg than in bulls of Swiss and Kalmyk breeds, respectively. The slaughter yield in young animals of all breeds was high from 60.1 to 61.6%. However, heavier carcasses were obtained from bulls of the Aberdeen-Angus breed, which is higher than that of Swiss and Kalmyk bulls by 6% and 12.9% at 18 months, respectively. The calorie content of carcass pulp in animals of all breeds was quite high (2274-2346 kcal at the age of 15.5 months and 2470-2700 kcal at 18 months).When determining the economic efficiency of growing bulls up to 15.5 and 18 months of age, it was revealed that the highest payment for feed was shown by animals of the Aberdeen Angus breed, which spent 11.1 per 1 kg of live weight gain for 15.5 and 18 months of growing, respectively.and 10.7 feed units. At the same time, the Aberdeen Angus breed had the minimum production costs per unit of production. In bulls at the age of 15.5 months, they were 5.3 and 17.0% lower than in Swiss and Kalmyk cattle, and at the age of 18 months, they were 11.1 and 20.3% lower, respectively.