Evaluation of candidate genotype of GH gene associated with growth, production and reproduction traits in Dairy Cows.

Growth hormone (GH) is a major regulator of postnatal growth and metabolism in mammals and plays a critical role in growth, production and fertility in cattle. The present study was conducted in dairy cattle to find the association of g.48769565 C > T mutation with growth, production and reproduction traits in Sahiwal and Hardhenu cattle. PCR-RFLP was performed to genotype g.48769565 C > T mutation using the MspI restriction enzyme in our resource cattle population. In Hardhenu cattle, the frequencies of C and T alleles were 0.59 and 0.41, respectively, while genotypic frequencies were 0.33, 0.53 and 0.14 for CC, CT and TT respectively. The frequencies of the C and T alleles were 0.24 and 0.76, respectively, in Sahiwal cattle and it was observed that the highest frequency was for the TT genotype (0.58) and the lowest was for the CC genotype (0.06). Chi-square analysis showed that g.48769565C>T SNP loci meet with the Hardy-Weinberg equilibrium in Sahiwal and Hardhenu cattle. From the least-squares analysis, it was observed that CC genotype was significantly associated with total milk yield (TMY), 300 days milk yield (300D MY), lactation length (LL), dry period (DP) and artificial insemination (AI)/conception (p < .05). We also observed a significant association (p < .05) of genotype CT with 3-month calves body weight. Cows with TT genotype revealed comparatively favourable service period (SP) and calving interval (CI) in our resource population. These observed differences in their allelic and genotypic frequencies in association with the traits underlying production and fertility can be utilized for genetic improvement in dairy cattle.