A STUDY ON IGF-1 AND IGFBP-3 GENES POLYMORPHISMS AND THEIR LINKED TO GROWTH TRAITS IN BARKI LAMBS

This study aimed to identify polymorphisms in the IGF-I and IGFBP-3 genes and to examine the associations between their SNPs and growth performance traits in Barki lambs. A total of 89 lambs were used to assess growth traits including body weights at birth, weaning six months, nine months, and one year. Average daily gain (ADG) was calculated over four intervals: from birth to weaning (ADG1), from birth to six months (ADG2), from birth to nine months (ADG3), and from birth to yearling (ADG4). The PCR-RFLP technique was employed to identify IGF-1 polymorphisms in the 5′ regulatory region and IGFBP-3 polymorphisms in exon 2. At the IGF-I locus, two genotypes (AA and BB) were identified; the allele frequencies were 0.70 for A and 0.30 for B, while the genotype frequencies were 0.70 for AA and 0.30 for BB. At the IGFBP-3 locus, three genotypes (CC, CG, and GG) were observed, with allele frequencies of 0.32 for allele C and 0.68 for allele G, with genotype frequencies of 0.09 (CC), 0.39 (CG), and 0.52 (GG). Association analysis indicated that both IGF-I and IGFBP-3 polymorphisms had a highly significant effect (P < 0.01) on growth traits. Lambs with the AA genotype of IGF-I showed higher weaning weights and superior ADG1 and ADG2 compared to those with BB genotype. For IGFBP-3, lambs with GG and CG genotypes exhibited higher body weights while both GG and CC genotypes showed better ADG compared to CC. These findings suggest that the polymorphisms of IGF-1 and IGFBP-3 could serve as molecular markers for breeding programs aimed the improving the growth traits of Barki sheep.