Studies On Effects Of IGF-â…¡ Gene On Partial Growth And Carcass Traits In Pigs

Using IGF- II gene as the main effect candidate gene of growth and carcass traits in pigs, adopting Polymerase Chain Reaction-Restrain Fragment Length Polymorphism (PCR-RFLP) to check the genotype in Nci I restriction locus, the genetic variation of IGF- H gene were detected in 528 pigs including 7 groups(Duroc YY, Landrace, Yorkshire XT, Yorkshire ZH, Ningxiang, Daweizi, Taoyuan), then the genotype frequencies and gene frequencies were counted according to the PCR-RFLP and the difference of genotype frequencies between groups were analyzed by Chi Square Test. At the same time, the effect on growth traits and carcass traits of IGF- II gene were estimated according to their growth and slaughter data. The main results are showed as follows:1. There were three Nci I restriction loci(locus A,B and C), locus A and B hadn't polymorphism in the testing population, locus C had polymorphism and the exhibition was three genotype: IGF- IIAA(900bp+400bp),IGF- IIBB(800bp + 400bp), IGF-IIAB (900bp+ 800bp+400bp) .2. The distribution of IGF- II genotype is different among 7 groups. No genetic variation was found in Yorkshire XT, the genotype was only IGF-IIBB, but in the Ningxiang and Daweizi, IGF-IIBB has't found. There is a significant difference among the breeds, and allele A is the superiority gene in locality breed, allele B is the superiority gene in foreign breed. The frequencies of Allele A in Daweizi Pig, Ningxiang Pig and Taoyuan Pig are 0.7549, 0.9062 and 0.7307; the frequencies of Allele B in Duroc YY, Landrace and Yorkshire ZH are 0.7445,0.6085 and 0.5761.3. IGF-IIAA is faster than IGF- IIBB on the growth traits in Duroc YY, Landrace and Yorkshire ZH, it's effect was 4.06%~8.31 %, allele A has the positive effect ongrowth speed. At the same time IGF- IIAA is thicker than IGF- IIBB on the back fat thickness traits, it's effect was 7.72 %~ 14.60%, allele B has the positive effect on meat percentage. Synthetically analyzing indicated that IGF- IT gene could regard as the main effect candidate gene of meat percentage traits in pigs.4. It can infer from the experiment that when IGF-IIAA pig's genome structure was change in the Nci I restriction locus as G-A, it can induce the IGF- II excessively expressing, and the quantity of IGF-II in the blood is rise. As IGF-II rising, the pig's fat sediment became fast correspondingly. As a result IGF-IIAA is thicker than IGF-IIBB on the back fat thickness traits, faster on the growth traits.The research reveals that genotype IGF-IIBB could be used as molecular marker on the back fat thickness traits.