Genetic Diversity of the Growth Hormone Gene and its Association with Reproductive Function in Jersey Cattle

Abstract

Introduction. The reproduction efficiency is critically important for the profitability of cattle breeding. The growth hormone gene (bGH) represents a promising candidate for investigating associations with economically important traits.
Aim. To examine the genetic diversity of the C/G polymorphism in the bGH gene and its associations with body weight, age and number of inseminations required for first successful conception in Jersey breed cows.
Materials and methods. The study was conducted on 361 Jersey breed cows. Zootechnical records of reproductive traits were analyzed in relation to genotyping results for the C/G polymorphism in the bGH gene (using PCR-RFLP). We calculated allele and genotype frequencies, tested for Hardy-Weinberg equilibrium and compared mean trait values between genotypes.
Results. The G allele was predominant in the population (0.59). Genotype frequencies were: C/C - 19.9%, C/G - 42.9%, G/G - 37.2%. A deviation from Hardy-Weinberg equilibrium (p < 0.05) with heterozygote deficiency was observed. Cows with the G/G genotype showed a tendency toward greater body weight but demonstrated significantly later age at first conception (p < 0.1) and required more inseminations to achieve conception (p < 0.05) compared to other genotypes.
Conclusions. The C/G polymorphism in the bGH gene is associated with early reproductive performance indicators in Jersey breed cows. The G/G genotype correlates with increased age at first conception and reduced fertility. The C/C and C/G genotypes may be preferable for selection based on early reproductive characteristics.