Meat productivity of sheep of the Altai Mountain breed of different genotypes according to the CAST and GDF9 genes

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%, GDF- 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.