The aim of this study was to investigate the association of five single nucleotide polymorphisms (SNPs) in GHR (growth hormone receptor), LEP (leptin), IGF1 (insulin-like growth factor 1), and IGF1R (insulin-like growth factor 1 receptor) genes with body weight at day 1, 33 and 90 of age and average weight gain at 1-33, 33-90 and 1-90 days of age in Pomeranian Coarsewool sheep. Blood samples were collected from 100 ewes derived from the only flock of this breed in Poland, and after DNA isolation, five selected loci were genotyped with use of appropriately designed PCR-RFLP assays. The g.122A>G in the GHR gene and the g.251G>A in the LEP gene were monomorphic, so only the effects of g.367G>T in the LEP gene, g.271C>T in IGF1 gene, and g.195C>T in IGF1R gene were investigated. The statistical analysis showed no association of the g.367G>A in LEP gene and g.271C >T in IGF1 gene with the selected growth parameters. In contrast, the g.195C>T polymorphism in IGF1R gene was significantly associated (P<0.001) with body weight and average daily weight gain. The TT genotype was linked to the highest values, while the CC genotype was linked to the lowest values, of the all analyzed traits. Thus, this study indicated the g.195C>T SNP as a potential genetic marker for growth traits. Nevertheless that effect should be investigated in other sheep breeds in order to confirm if that SNP can be used for marker-assisted selection.

Key words: Growth traits, IGF1R gene, Polymorphism, Sheep