Relationship Between GHRL Gene Polymorphisms and Growth Traits in Pigs

Ghrelin (GHRL) is a gastric endocrine hormone, which has biological functions of regulation of appetite, body weight, gastrointestinal motility and growth hormone secretion. The aim of this study was to investigate the novel single nucleotide polymorphisms (SNPs) at GHRL gene in three different pig breeds, including Duroc, Yorkshire and Landrace, and the association of the novel SNPs with growth traits. PCR-SSCP and sequencing were used to detect the GHRL gene polymorphisms in the present study. Three SNPs were detected, one in the exon 1 (g.3734 G>T), which was synonymous, and two SNPs in intron 4 (g.7691 A>C and g.8523 T>C). The sites g.3734 G>T and g.7691 A>C had significantly impact on body weight at 21 days (BW21) and body weight at 70 days (BW70), the days when the pigs reached the target weights of 30 kg(D30) and 100 kg(D100), average daily gain between 30 kg and 100 kg (ADG), and backfat thickness of 100kg body weight (BFT) (P < 0.05 or P < 0.01), while did not contribute birth weight and days to 50 kg body weight(D50) (P > 0.05). At g.8523 T>C site, compared to TC genotype, the individuals with TT genotype in Duroc had greater D100 and BFT (P < 0.05 or P < 0.01), which had lower ADG between 30 kg and 100 kg (P < 0.01). In Yorkshire and Landrace, the polymorphism g.8523 T>C had no effect on the tested traits (P > 0.05). Our findings suggested that the 3 sites (g.3734 G>T, g.7691 A>C and g.8523 T>C) polymorphism in porcine GHRL gene might be one of the useful genetic marker in pig breeding and which needed to be further studied.