Abstract:

【Objective】Ghrelin (GHRL) gene plays an important role in chicken growth and development and it is a candidate of great interest for growth and carcass traits. In this study, association analyses were carried out between polymorphisms of the GHRL gene and chicken growth and carcass traits.【Method】Six SNPs of the GHRL gene were genotyped in a F2 full sib chicken population and two commercial populations to investigate their associations with production traits, mRNA expression in glandular stomach and plasma GHRL level. Then the interaction between A-2220C in 5′ flanking region of the chicken GHRL gene and nuclear proteins was analyzed to confirm the effect of this DNA fragment on gene transcription by electrophoretic mobility shift assay (EMSA) method.【Result】Marker-trait linkage study showed that A-2220C was significantly associated with birth weight (P＜0.05). Moreover, A allele was positive for chicken birth weight as individuals with AA genotype had the highest value. C-2399Del was significantly associated with body weight (BW) at 56 days, daily gain from weeks 0 to 4, breast muscle weight (BMW), as well as wing weight (WW) (P＜0.05). Meanwhile, individuals with
CDel genotype had the highest value of these traits. On the other hand, haplotypes composed of these 6 polymorphisms were significantly associated with body weight at 42(BW42) and 70(BW70) days of age daily gain from weeks 0 to 4, daily gain from weeks 4 to 8, dressed weight, eviscerated weight, eviscerated weight with giblet, and BMW (P＜0.05), and they were also significantly associated with birth weight and body weight at 21(BW21), 28(BW28), 35(BW35), 49(BW49), 56(BW56) and 90(BW90) days of age (P＜0.01). Furthermore, individuals with haplotype H3H4（CCAAAC\CCAACDel）was positive for chicken growth compared to individuals with other haplotype combinations. The results of EMSA showed that fragment with A allele of A-2220C could bind the nucleic protein, whereas that with C allele was free of binding activity. And it suggested that this DNA fragment has some effect on the GHRL gene transcription.【Conclusion】The polymorphisms of the 5′ flanking region of GHRL gene are significant association with chicken growth and carcass traits.