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.

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The aim of the study was to assess the genetic potential in Canadian Hereford sires using DNA markers, identify complex genotypes and assess their impact on the growth, development and meat productivity of its offspring. Groups of sons were formed taking into account the complex genotypes of sires: group 1 (n = 28) – sons of bulls carrying in their genome a complex of genotypes with desired alleles; group 2 (n = 30) – sons of bulls with a complex of genotypes that lack the desired alleles. The offspring from bulls-carriers of the “desirable” alleles in complex CAPN1, GH, Lep, TG5 genes that meet the exterior requirements exceeded their peers in live weight (P < 0.05), carcass weight (P < 0.05) and muscle tissue (P < 0.05). The maximum conversion rate of feed protein into product protein was also established in the group of sons from selected bulls. Thus, animal selection for body conformation type is advisable to combine with the herd genotyping for a complex of genotypes associated with different economically useful traits when creating highly efficient population of beef cattle.

The article presents the results of the analysis of the fatty acid composition of the lipids of the muscle tissue of sheep of diff erent genotypes of the Stavropol breed at the age of 8 months. The polymorphism of the calpastatin CAST gene was determined using PCR-PDRF.

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