Studies On Polymorphisms Of PGC-1, MC4R Genes And Their Relarionships With Main Economic Traits In Pigs

In this experiment,SNPs of PGC-1 and MC4R genes were detected in Yorkshire,Landrace, Duroc,Minpig and hybrid sows by Sequencing,PCR-SSCP and PCR-RFLP,in the meantime,the distribution for genotypes frequencies and alleles frequencies of these SNPs in six populations and their effects on growth,carcass and meat quality traits were studied in different populations.The study analyzed the relationship between reproductive performance and backfat thickness of sows during breeding,parturition or weaning and the affection of backfat loss during lactation on reproductive performance next parity for gaining the best backfat thickness during breeding and lactation.The results are as follows:(1) The PGC-1 Exon8 was detected.There was one polymorphic site in the(T→A) site.A T→A mutation that caused the amino acid Cys to Set.The polymorphism in exon8 of PGC-1 gene was associated with Average daily gain and backfat thickness concentration in Yorkshire and Landrace populations(p＜0.05).The sows of AA genotype had higher Average daily gain than the sows of BB.A allele gene was superiority.But the sows of BB genotype had lower backfat thickness than the sows of AA.B allele gene was superiority.Meanwhile,the polymorphism in exon8 of PGC-1 gene was associated with ante partum backfat thickness concentration in Yorkshire and Landrace populations(p＜0.05).B allele gene may lead to the excessive deposition of backfat of primiparous sows during gestational period.(2)The PGC-1 Exon9 was detected.There was one polymorphic site in the(A→C) site.An A→C mutation that caused the amino acid Pro to Thr.The polymorphism in exon9 of PGC-1 gene was associated with carcass length and Water-Holding Capacity concentration in DLY populations (p＜0.05).The sows of AA genotype had lower carcass length and Water-Holding Capacity than the sows of BB.A allele gene was superiority.(3)There was One polymorphism locus of StyI in the(A→G) site.The mutation is silent mutation.The polymorphism locus of StyI was associated with the backfat loss during lactation concentration in Yorkshire populations(p＜0.05).The sows of BB genotype had higher backfat loss during lactation for high lactation.It was not conducive to estrus-service interval and reproductive performance of next parity.(4)One polymorphism locus of BanⅢ(G117A) which resulted in a change of amino acid,i.e. lle→Met was detected in partial coding sequence of MC4R gene.The polylnorphism locus of HindⅢwas associated with the measured backfat thickness concentration in DLY populations(p＜0.05). The sows of AA genotype had lower measured backfat thickness than the sows of BB.A allele gene was superiority.(5)One polymorphism locus of BanⅢ(A892G) which resulted in a change of amino acid,i.e. Asn→Asp was detected in partial coding sequence of MC4R gene.The polymorphism locus of BanⅢwas associated with the Average daily gain and backfat thickness concentration in Yorkshire and Landrace populations(p＜0.05).The sows of BB genotype had higher Average daily gain than the sows of AA.B allele gene was superiority.But the sows of AA genotype had lower backfat thickness than the sows of BB.A allele gene was superiority.The polymorphism locus of BanⅢwas associated with the intramuscular fat content concentration in DLY populations(p＜0.05).The sows of BB genotype had higher intramuscular fat content than the sows of AA.So B allele gene was superiority.(6) The phenotypic correlations estimates for the corrected backfat thickness and average backfat thickness of gilts during breeding with number born alive were 0.204 and 0.210 for first parity,they had a high and positive correlation with number born alive.The phenotypic correlations estimates for the corrected age with number born alive was-0.105 for first parity,they had a high and negative correlation with number born alive.It showed that gilts which had fast growing and backfat deposition during breeding were conducive to number born alive and litfer weight of piglets on day 21.The high backfat thickness of primiparous and multiparous sows during parturition was not conducive to number born alive,but it was conducive to litter weight of piglets on day 21.The average backfat loss during lactation had negative phenotypic correlation with subsequent total number of piglets born alive-0.346 and positive phenotypic correlation with litter weight of piglets on day 21 0.201.Because of its impact on other reproductive traits,backfat loss during lactation should receive attention in pig breeding.(7) When the backfat thickness of gilts was 15.5-20.0 mm during breeding,it was conducive to number born alive and litter weight of piglets born.When the backfat thickness of primiparous and multiparous sows was higher than 25 mm during parturition,the reproductive performance had an adverse impact.When the backfat thickness of sows was 17.5-22.5mm during parturition,it was conducive to estrus-service interval and reproductive performance of next parity.When the backfat loss of sows was higher than 5.5mm during lactation,the empathema after weaning and reproductive performance of next parity of sows may be affected.