Association of Leptin Gene (LEP) Polymorphism with Growth Rates and Milk Production in Holstein First-Calf Heifers

The objective of the work is to study the polymorphic leptin gene variants and their influence on growth, development, and milk production of Holstein first-calf heifers, whose 172 blood samples were analyzed. Genotyping the leptin gene locus was performed with the PCR-RFLP method. The frequencies of occurrence of the C and T alleles comprised 0.62 and 0.38, respectively; the values for genotypes CC, TC, and TT comprised 35.5% (61 animals), 53.3% (90 animals), and 12.2% (21 animals), respectively. It was ascertained that the analyzed animal population is in the genetic balanced equilibrium state according to the Hardy–Weinberg law. Under similar conditions of feeding and nutritional supplement, the animals having genotype CC were significantly superior to their peers with the other genotypes in all the parameters characterizing the live weight at different ages. However, the milk yield, the fat mass fraction, the milk fat yield, and the milk protein yield in the specimens having the TT genotype were higher by 8.9% ( P ≤ 0.01; 673.4 kg), 0.20, 12.9% ( P ≤ 0.05; 38.4 kg), and 9.0% ( P ≤ 0.05; 22.7 KG), respectively, than that in the genotype TC carriers. The coefficient of milkability was 142.1 kg higher in all the first-calf heifers when compared to the lower value for the entire herd, therefore, indicating the specific dairy type of the analyzed animal population. The obtained data can prove the associations between the different genotypes of the leptin gene and the growth rates, the physical development, and the milk production in Holstein cattle.