Abstract
Abstract. Kazakh meat–wool sheep are of great interest because of the intrabreed multifetal type's high productivity of 140 %–160 %. Genes encoding growth differentiation factor-9 (GDF9) and bone morphogenetic protein 15 (BMP15) are promising candidates for studying sheep productivity, as they affect fertility in mammals, including sheep. Thus, the purpose of this study was to assess the fertility of the Kazakh meat–wool sheep breed based on GDF9 and BMP15 candidate genes of fecundity for the selection of animals with valuable genotypes. We selected 300 heads of the Kazakh meat–wool sheep breed from two populations for PCR-RFLP (polymerase chain reaction–restriction fragment length polymorphism) analysis, 15 of which were subsequently used for sequencing of exon regions of the GDF9 and BMP15 genes. The sheep populations were tested for G1 and G8 mutations of the GDF9 gene and B2 and B4 mutations of the BMP15 gene. The PCR-RFLP analysis revealed that 59 (19.7 %) of the 300 Kazakh meat–wool breed sheep were heterozygous carriers of the G1 mutation (genotype AG) of the GDF9 gene, and sequencing analysis supported these results. The comparative phylogenetic analysis showed a clear separation of Kazakh meat–wool sheep wild types and carriers of the G1 mutation. This mutation was reported to have a relationship with the animals' litter size in other sheep breeds. For this reason, similar relationships should be investigated in Kazakh meat–wool sheep. However, G8, B2, and B4 mutations were not detected among the studied animal populations, showing that these mutations are not characteristic of the Kazakh meat–wool sheep breed.