The successful development of sheep farming in the meat sector is largely determined by the use of molecular genetic methods and modern genotypes. The Altai Mountain breed of sheep optimally combines high wool and meat with unsurpassed adaptability to grazing in the highlands of the Altai Republic throughout the year. The genes of calpastatin (CAST) and differential growth factor (GDF9) are considered as promising markers of quantitative and qualitative signs of sheep meat productivity. It was established that in the Altai Mountain breed the polymorphism of the CAST and GDF9 genes is represented by three genotypes MM, MN, and NN; AA, AG and GG with a frequency of occurrence of 0.23; 0.72 and 0.05; 0.10; 0.35 and 0.55, respectively. The level of homozygosity (Ca) in the CAST gene was 73.1%, GDF9 – 60.6%. The level of effective alleles (Na) was higher in the GDF9 gene (1.65) compared with CAST (1.44). The level of factual (Ho) and theoretical (He) expected heterozygosity for the GDF9 gene was 0.538 and 0.651, respectively, for the CAST gene – 0.290 and 0.368, which indicates a certain lack of heterozygotes in both genes. The analysis of slaughter qualities established the superiority of carriers of the NN genotype over the MM genotype in the CAS gene in terms of pre-slaughter and carcass weight, meat ratio by 4.96 and 2.83 kg, respectively (P<0.05), 0.26 units (P<0.05). In the GDF9 gene, the AA-type sheep exceeded the peers of AG and GG-genotypes in the pre-slaughter weight, carcass weight and its output, meat ratio by 1.62 and 7.01 kg, respectively; 1.34 and 3.98 kg (P<0.05); 1.21 and 1.86 abs. percent; 0.16 and 0.39 (P<0.05) units.

A large number of works are devoted to the development of the skin and hair cover of sheep, depending on their breed affiliation, age, feeding conditions and housing. The authors point out that along with other conditions the quality of wool and wool clip is greatly influenced by the conditions of the feeding of animals. A high level of feeding increases the wool clip and improves the quality of the wool and vice versa a low level reduces, causes thinning and worsens other physical properties of the wool. As is known, one of the significant factors that determine the increase in wool clip is the size of the animal and, consequently, the total area of the skin. The purpose of the research was to investigate the morphological traits of the development of the skin and wool cover in sheep of Prikatunsky meat and wool type. The research material was wool samples from four topographic areas of the animal’s body (side/thigh/back/belly) and skin (side) of different sex and age groups, selected from the animals of the studied groups. In the course of research, the quality of wool and indicators of the histostructure of the skin of Prikatunsky meat and wool type of sheep have been investigated. In terms of thick-haired of wool, replacement rams and gimbers of Prikatunsky meat and wool type of sheep were superior by 4,82 pcs. per mm² or 19,0 % and 4,41 pcs. per mm² or 15,8 % of adult animals, respectively. Balance secondary follicles/primary follicles in young animals were higher by 10,3 and 17,3 % compared to breeding rams and ewes. The wool of the replacement young animals was thinner by 7,28 and 4,78 microns and they were more thick-haired. The obtained data will be used in the mating campaign when mating program rams in order to improve the sheep of Prikatunsky meat and wool type.

In recent decades in many countries of the world the development of sheep farming is determined by the efficiency of mutton production. One of the promising areas of selection improvement of sheep breeds of meat and meat & wool productivity is an application of molecular-genetic methods. To obtain high-quality mutton it is advisable to use the Altai Mountains sheep breed, which features by high energy of growth of young animals and their adaptability to all-year-round pasture management. One of the candidate genes responsible for sheep meat productivity is the gene of growth differentiation factor -GDF9 (growth differentiation factor 9). The article presents the results of research of polymorphism of the gene GDF9 and its relation with the parameters of meat productivity in young sheep of Altai Mountains breed. It was found that the rams-carriers of AA genotype outperformed their peers of AG and GG genotypes in terms of pre-slaughter weight, carcass weight, meat yield and meat content ratio by 1.62 and 7.01 kg, 1.34 and 3.98 kg (P<0.05), 1.21 and 1.86 abs. percent, 0.16 and 0.39 units (P<0.05) accordingly. The muscle tissue of rams of the desired genotype featured the highest content of protein, fat and, accordingly, energy value in comparison with AG and GG genotypes. The animals of AA genotype had the largest area of a rib eye and diameter of muscle fibers. The superiority over other genotypes achieved 1.55 cm 2 and 1.98 microns in average. In addition the higher number of inter-fiber and inter-bundle inclusions of fat and lower content of connective tissue stipulated higher marbling score (MB)-higher by 3.32 points. The obtained data indicate that it is promising methods to increase the number of homozygotic animals in term of gene GDF9 by intended selection of parent animals whose genotype contains a desirable element for further improvement of quantitative and qualitative parameters of meat rate productivity in sheep of Altai Mountains breed.

The main number of sheep in the Russian Federation is currently concentrated in peasant (farmer) and personal farms, where the level of breeding work is often very low. Despite this, there is a huge reserve of mutton production in these categories of farms. The purpose of the work was to study the productive traits of sheep of Prikatun breeding type of Mountain Altai breed under the conditions of peasant (farmer) farms in the Altai Republic. The experimental part of the research was carried out on the basis of the farm “Usoltseva N. A.” in the Ust-Kansky area in the Altai Republic. The object of the study were the mature ewes sheep of Prikatun breeding type of Mountain Altai breed, their off spring aged from birth, 4 and 6 months, before slaughter, as well as carcasses obtained during slaughter. Under the conditions of the Altai Republic with year-round pasture content in sheep of Prikatun breeding type of Mountain Altai breed a complex study of milk productivity and the chemical composition of sheep’s milk was carried out. New data on the eff ect of age, live weight, prolifi cacy, polymastia, off spring sex and morphometric measurements of the udder on the milk production of sheep have been obtained. The infl uence of the level of milk content of sheep of Prikatun breeding type of Mountain Altai breed on the growth, development and meat productivity of lambs has been studied. It was found that lambs received from mothers with high milk capacity had a higher growth rate in all the studied age periods. The young animals of this group were characterized by better meat productivity and as a result had a higher level of profi tability, which amounted to 53,35 %. Taking into account the infl uence of the level of milk production of ewes of Prikatun breeding type on the growth and development of lambs, we recommend that peasant (farmer) farms of the Altai Republic, in order to increase the production of mutton, select ewes for the fi rst 20 days of lactation with a milk yield of at least 21 kg of milk.

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