Analysis of Growth Hormone Gene Polymorphism and Its Association with Growth Traits in Kenguri Sheep

Abstract— The present study investigated polymorphisms of the growth hormone (GH) gene and their association with morphometric traits in Kenguri sheep, an important meat-type breed of Karnataka, India. A total of 60 adult sheep (16 males and 44 females) were sampled for genomic DNA isolation using a modified high-salt method. The GH gene fragment (422 bp) spanning exon 2–3 was amplified through polymerase chain reaction (PCR) and genotyped by PCR–restriction fragment length polymorphism (PCR-RFLP) using the HaeIII enzyme. Two genotypes, AA and AB, were detected, while BB was absent. The frequencies of AA and AB genotypes were 0.417 and 0.583, respectively, with allele frequencies of 0.708 (A) and 0.292 (B). Chi-square analysis indicated significant deviation from Hardy–Weinberg equilibrium (χ²=10.29, p<0.05). Morphometric traits including body weight, body length, height at wither, and chest girth were recorded. Males showed significantly (p<0.05) higher body weight and chest girth than females, while other traits were comparable. Within genotypes, no significant association (p>0.05) was found between GH polymorphisms and body measurements in either sex. The findings confirm the presence of GH gene variability in Kenguri sheep, with predominance of heterozygotes, although no strong phenotypic association was evident. This suggests that while the GH gene harbours genetic variability, additional markers or larger populations may be required to elucidate its role in growth performance. The study provides baseline molecular information that could support marker-assisted selection (MAS) strategies for sheep improvement programs in India.