Polymorphism of the Growth Hormone Gene (G.2141C>G) in Cattle Populations: Analysis of Reproductive Traits

A polymorphism (g.2141C>G) of the growth hormone (GH) gene was studied in the populations of cows of the Ukrainian red-spotted dairy, Montbeliard breeds, and crossbreeds obtained from the crossing of Ukrainian red-spotted dairy cows with Montbeliard bulls, and the analysis of reproductive traits of individuals with different genotypes was conducted. Genotyping of the growth hormone gene was carried out using a PCR–RFLP method. Both L and V alleles were detected in the experimental cow populations. The ratio of the frequencies of LL/LV/VV genotypes did not differ from the theoretically expected one for each of the experimental groups (χ² = 0.91, p < 0.05; χ² = 1.41, p < 0.05; χ² = 1.66, p < 0.05, respectively). In the experimental populations of the Montbeliard breed and crossbred animals, the VV genotype frequency was 0.03 and 0.06, respectively; no VV genotype was detected in the population of the Ukrainian red-spotted breed. According to the traits of reproductive function, the cows of the experimental groups with the LL genotype variant had better indices as compared with their peers with the LV genotype: an earlier age of first insemination, lower index of insemination, and shorter intercalving period. According to the live weight at birth and growth dynamics in each experimental group of cows, the carriers of the LV genotype had an advantage. Regardless of the genotype, higher indices of live weight at birth and average daily growths were established in animals of the crossbred origin as compared with purebreds. The established polymorphism of the growth hormone gene (SNP g.2141C>G) indicates a feasibility of further studies and prospect of using it as a genetic marker of reproductive ability in marker-assisted selection of dairy cattle direction of productivity.