Evaluation of insulin-like growth factor-I gene polymorphism on growth traits and yearling fleece weight in goats

The PCR-SSCP analysis of the 5′ flanking region of the goat insulin-like growth factor-I gene (gIGF-I) was used to screen polymorphisms in a total of 296 goats belonging to two breeds of goats (Markhoz and Kurdi) reared in the Kurdistan province in Iran. The PCR products of different electrophoresis patterns were sequenced and aligned. Sequencing revealed a novel G to A transition at position 422 bp upstream from the ATG codon (g.1617 G > A), according to the GenBank sequence D26119.2. PCR-RFLP analysis of part of intron 4 and exon 4 of the goat IGF-I gene was used to identify associations between the intron 4/HaeIII polymorphism and economic traits. Results of fixed model analysis revealed that the intron 4/HaeIII polymorphism was significantly associated with yearling weight (YW), post-weaning average daily gain from 3-months to 12-months (ADG4), 6-months to 12-months (ADG6), 9-months to 12-months (ADG7), and first shearing fleece weight (FSFW) (P ≤ 0.05). Animals that possessed the GG genotype for the intron 4/HaeIII mutation appeared potentially more favorable for all mentioned traits. These results suggest that variation in the caprine IGF-I gene is associated with growth traits and yearling fleece weight in Markhoz goats.