Evaluation of Polymorphism in IGF-I and IGFB-3 Genes and their Relationship tith Twinning Rate and Growth Traits in Markhoz Goats

Growth rate and twinning rate are economic traits that can be used in goat breeding objectives. The aim of this study was to investigate polymorphisms in the insulin-like growth factor 1(IGF-I) and insulin-like growth factor binding protein (IGFBP-3) genes and their relationship with growth traits and twinning in Markhoz goats. Two sets of specific primers were used to amplify a 249bp fragment of IGF-I gene and a 316bp fragment of IGFBP-3 gene. PCR-SSCP analysis revealed three banding patterns for each gene that confirmed presence of a mutation in position 1617 of the IGF-I gene and a mutation in position 58 of IGFBP-3 gene. The genotype frequencies of IGF-I gene were 0.81 (GG), 0.16 (GA) and 0.03 (AA). Also, the genotype frequencies of IGFBP-3 gene were 0.79 (TT), 0.17 (TC) and 0.04 (CC). The Odds Ratio estimated for twinning rate was 1.11 for second on first parity, 0.19 for third on first parity and 5.71 for second on third parity. The chi-square statistics were 6.46 for IGF-I gene and 3.32 for IGFBP-3 gene. The results also indicated that different genotypes of these genes had no significant effect on birth weight, weight at 6 months, at 9 months and at 12 months but the interactions between different genotypes of IGF-I and IGFBP-3 genes were significant for weaning weight and average daily gain from birth to weaning. These results suggest that twinning rate in Markhoz breed is statistically affected by these genes and can be considered in breeding programs.