New correlations between IGF1 gene polymorphisms and some production and physiological traits in broiler chicken

This study investigated the association between SNP in 5’UTR region of insulin-like growth factor-1 gene and phenotypic productive and physiological traits in Cobb and Hubbard broiler breeds. The study was conducted in poultry farm – Animal resources department – College of Agriculture – University of Baghdad during a period from 1 September 2014 to 1 February 2015. Three hundred broiler chicks at one-day old (150 Cobb and 150 Hubbard) were wing-banded and reared under optimal conditions according to the guide and fed ad libitum. Live body weights and body weight gains were recorded weekly. A sample of broilers at 49 days of age were slaughtered for carcass cuts analysis and blood collection was done to obtain fresh blood for analysis of RBCs, Hb, PCV, WBCs and differential count; and serum for biochemical and hormonal analysis. DNA was extracted from fresh blood samples. Polymerase chain reaction (PCR)- restriction fragment length polymorphism (RFLP) method was used for detection the polymorphism in the 5’UTR region of insulin-like growth factor-1 gene. Then the results were confirmed by sequencing. All parameters studied herein were compared according to the TT, TC and CC genotypes. Cobb broilers with TT genotype had significantly (p˂0.05) higher heterophil values and serum triglyceride concentrations than those of other genotypes. Cobb broilers with TC genotype had significantly (p˂0.05) higher breast, gizzard and back weights and body lengths than those of other genotypes. Cobb broilers with TC genotype had significantly (p˂0.05) lower serum IGF-1 concentrations than those of other genotypes. In Cobb breed, male and female broilers with CC genotype had significantly (p˂0.05) lower AST concentrations than other genotypes. Hubbard broilers with TT genotype had significantly (p˂0.05) higher values of wing weights, WBCs, eosinophil and LDL concentrations than those of other genotypes. Hubbard broilers with TC genotype had significantly (p˂0.05) higher breast weights, breast circumferences and ALT concentrations and lower AST concentrations than those of other genotypes. In Hubbard breed, the increase in the concentrations of serum total protein and serum thyroxine was associated with C allele. Male broilers with TC genotype had significantly (p˂0.05) higher breast weights, heart weights, RBCs and heterophil values and lower drumstick and giblet weights than those of other genotypes. Male broilers with CC genotype had significantly (p˂0.05) higher WBCs and sternum bone lengths than those of other genotypes. In male broilers, the increase in serum albumin concentrations was associated with C allele. Female broilers with TT genotype had significantly (p˂0.05) higher LDL concentrations and liver weights than those of other genotypes. Female broilers with TC genotype had significantly (p˂0.05) higher weights of breast, gizzard, heart and neck, also, body lengths, breast circumferences and serum total protein than those of other genotypes. Female broilers with CC genotype had significantly (p˂0.05) higher carcass weight, RBCs, Hb and PCV values than those of other genotypes. In female broilers, the increase in back weight and dressing percentage was associated with C allele. In this study, 21.4, 23.8, 26.2 and 40.5% of parameters studied herein were affected by IGF-1 polymorphism in Cobb, Hubbard, male and female broilers, respectively. In addition, the majority of the improvement in economic traits was associated with C allele.