Polymorphism in GH and GHR loci and its association with phenotypic and breeding values of body weight traits in breeder hens of Mazandarn native fowls breeding station

The chicken growth hormone gene is considered as one of the most important candidate genes that can influence chicken performance traits because of its crucial function in growth and metabolism. In order to detect polymorphism in GH and GHR loci 160 blood samples were collected randomly from breeder hens of Mazandaran native fowls breeding station. DNA was extracted using modified salting out procedures and polymerase chain reaction (PCR) were used for amplification of fragments with the length of 1050 bp at GH and 718 bp at GHR loci. The treatment of fragments at GH and GHR loci with SacI and HindIII restriction enzymes were revealed +، - and A and B alleles، respectively. The frequencies of alleles at GH locus were + (0. 7981)، - (0. 2019) and for GHR were A (0. 9937) and B (0. 0063). The genotype frequencies were +/+ (0. 6153)، +/- (0. 3653) and -/- (0. 0192) for GH locus and AA (0. 9937) and BB (0. 0063) for GHR locus. Low heterozigosity of GH gene could be due to closed and small effective number size of flock. Phenotypic analysis showed that GH genotypes were significantly affected body weight (BW) at 12 weeks of age (P≤0. 03). Comparison of means indicated that +/+ genotypes had higher BW at 12 weeks than the other genotypes. The relationships between GHR and other GH genotypes with phenotypic data or breeding values traits were not significant (P>0. 05).