Study On The Polymorphisms Of IGF-â…  Gene And Correlative Analysis With Weight Traits Of Liangshan Semi-wool Sheep

Insulin like growth factor I stimulate the growth of animal in embryo period and the developing of post birth period with mediating the neuroendocrine function of chondrotropic hormone.It is vital physiological effectiveness which are regulating carbohydrate metabolism,fat metabolism,protein synthesis,liver function and linear growth of all livestock.The polymorphisms of IGF-I gene were detected by PCR-SSCP method among 587 Liangshan semi-wool sheep from 8 populations developed by Liangshan prefecture.Based on the detection of polymorphisms,the effects of different genotypes on weight traits were analyzed.The results were as follows:The results showed that the effect of family,year and genotype influenced the weight traits on different degree.The effect of family of primer 1 influenced the Birth weight,the Weaning weight,the Weaning daily weight and the 30-month weight in very significantly (P＜0.01) and had the significant influence to the 18-month weight(P＜0.05).The effect of year influenced the Birth weight,the Weaning weight and the Weaning daily weight in very significantly(P＜0.01).The effect of genotype influenced the Birth weight in very significantly(P＜0.01).The effect of family of primer 2 influenced the Birth weight,the Weaning weight,the Weaning daily weight and the 30-month weight in very significantly (P＜0.01).The effect of year influenced the Birth weight,the Weaning weight and the Weaning daily weight in very significantly(P＜0.01).The effect of genotype influenced the Weaning weight and the Weaning daily weight in very significantly(P＜0.01).The effect of sex had the significant influence to the Weaning weight and the Weaning daily weight (P＜0.05).There are two SNP sites in the Pre-district and the third exon region of IGF-I gene, they are C900G and A2054G.The genetic parameters were calculated,and the results showed:IGF-I-900SNP site had intermediate Polymorphism Information Content (0.25＜PIC＜0.5).IGF-I-2054SNP site had low PIC.IGF-I-900SNP PIC=0.2756,IGF-I -2054 PIC=0.2368,which was suitable for the weight traits associated with the production of statistical analysis.The x~2 agreement test showed that the SNP1 site was strayed off the Hardy-Weinberg equilibrium(P＜0.01),but the SNP2 site was in Hardy-Weinberg equilibrium(P＞0.05).The SNP1 site influenced the Birth weight in significantly(P＜0.05),and the AA genotype had the addictive effects to the weight traits.It had no significant influence to the Weaning weight,the Weaning daily weight,the 18-month weight and the 30-month weight.The SNP2 site influenced the Weaning weight and the Weaning daily weight in significantly(P＜0.05).The CC genotype had significant higher difference than CD (P＜0.05),and mainly had the positive additive effect of increasing 1.7400,23.7350 and 29.3350.Through the haplotype analyzed,the frequence of H1(AC) is 74.31%,the frequence of H2(AD) is 4.74%,the frequence of H3(BC) is 11.70%,the frequence of H4(BD) is 9.25%.The haplotype H1 and H3 have the advantage.The frequence of H1 and H3 are higher than the haplotype H2 and H4.The distribution of IGF-I genotype in M1 strain strayed off the Hardy-Weinberg equilibrium(0.01＜P＜0.05),but all the other populations were in Hardy-Weinberg equilibrium(P＞0.05).The results by LSM(least square means) analysis and significant test showed that the haplotype combinationthe of the IGF-I gene influenced the Birth weight,the Weaning weight and the Weaning daily weight in significantly(P＜0.05),but had no significant influence to the 18-month weight and the 30-month weight(P＞0.05).