Effect of Prolactin Gene Polymorphisms on Egg Weight of White Leghorn and Hy-line Brown Laying Hen Strains

Abstract

This study was conducted at Poultry farm and Poultry Physiology laboratory /Animal Resources Department / College of Agriculture / The University of Baghdad during a period from 26/September/2013 to 1/June/2014 to find out the association of prolactin (PRL) gene polymorphisms with egg weight of laying hens. Two strains of laying hens, White Leghorn (n=100) and Hy-line Brown (n=60) were used in this study and reared in individual cages .Blood samples were collected from a brachial vein at 41 weeks of age. The PRL gene polymorphisms were determined using PCR-RFLP technique and AluI restriction enzyme. Two alleles C and T and three genotypes wild type CC (homozygous), heterozygous CT and mutant TT (homozygous) have been got. The size of the target gene fragment was 439 bp. A significant (p < 0.05) difference was showed in the Brown strain between genotypes CC and TT, the genotype CC was higher than TT in egg weight ( EW) at 34 week of age, in White strain there was a significant (p < 0.05) differences between CC and CT, also, CC with TT genotypes in EW at 30 week of age. The T allele frequency was 0.66, whereas, C allele frequency was 0.34 for Brown strain. In White strain, the C allele frequency was 0.98, whereas T allele frequency was 0.02. The distribution percentage of polymorphism of PRL gene in Brown strain were 56.60, 37.74 and 5.66 % for CT, TT and CC genotype respectively, whereas, the distribution percentage of polymorphism of PRL gene in White strain were 97.75, 1.12 and 1.12 % for CC, CT and TT genotype respectively, and the differences among percentages was significant (p <0.01). The allele frequency and distribution percentage of polymorphism for PRL gene was measured according to Hardy-Weinberg equilibrium.