Abstract
Modern cattle breeding is characterised by the need to select specific animals with extraordinary meat performance, as well as an ability to adapt to the natural environment in order to develop new, improved breeds. As Auliekol and Kazakh white-head races are especially interesting to farmers in Kazakhstan, we chose to study three polymorphs of somatotropic cascade genes: bPit-1, bGH and bGHR in the whole blood of such animals, which are known to have an impact on meatiness and good health. The following polymorphic variations were revealed: bPit-1-HinFI and bPit1-HinF1; bGH-AluIV and bGH-AluIL, as well as bGHR-SspIY and bGHR-SspIF. The agreement of the observed frequencies of genotypes with those theoretically expected according to the Hardy-Weinberg law of balance was also assessed. The final task was to compare the frequency of appearance of polymorphic genes alleles’ with somatotropic cascade distribution in the examined animals. Our studies have shown that the frequency of the genotypes’ occurrence in both races is in compliance with the frequency based on the law of balance. We suggest that the polymorphisms of the cascade network may result from the breeding progress achieved by directional selection, therefore conditioning high values of meat and health characteristics in the examined cattle.