Relationship between STAT5B Candidate Gene Polymorphism with Growth Related Traits and Ascites Index in Commercial Chicken Line

Ascites syndrome, also called pulmonary hypertension syndrome is a major concern of the poultry industry for decades. There have been a numerous reports regarding the underlying genetic variability of different breeds/strains in resistance against ascites. This scenario indicates gaining deep insight into the genomes of chicken pure lines, in order to find the favorable alleles within candidate genes controlling the variation of resistance/susceptibility to ascites. In this context, the aim of the present work to study the polymorphisms within STAT5B gene in the B line of Arian strain and to investigate the potential association of the confirmed polymorphism with body weight and growth rate traits at different ages as well as with carcass-related traits and ascites indicator traits. For this purpose, in overall, 166 birds, which their health status has previously been confirmed via clinical trials was chosen for genotyping the STAT5B gene in a polymorphic site using PCR-RFLP and MspI restriction enzyme. Enzymatic digestion results identified three AA, AG and GG genotypes with 0.46, 0.44 and 0.1 frequencies, respectively. Birds carried GG genotype were significantly (P<0.01) heavier in body weight (8-10%) or faster in growth rate (12-13%) than other genotypes all over of the rearing practice, particularly at 14-21 days of age. Furthermore, this genotype group was affected the heart weight considerably (P<0.10). However, there were no significant differences between the least square means of the remaining carcass related traits of the three genotypes. Moreover, the obtained outputs verified that there is no significant difference between the STAT5B genotype and allele frequencies between the healthy and ascites birds. Finally, it can be concluded that, the mutation of adenine to guanine substitution improves body weight and growth rate, but this polymorphism has nothing to do with ascites. This finding may emphasis to the fact that, despite the previous thoughts about the direct relationship of the genes controlling the ascites and growth, genes improving the body weight or growth rate do not have a direct influence in increasing the incidence of ascites. Further research is needed in order to be able to propose a general conclusion about the association of genes affecting the ascites and growth.