Genetic Analysis Of Main Meat-Producing Traits And Industrialization Application In Shanxia Black Pigs

Pigs are important livestock,as they are a main source of animal protein for many people in the world.Breeding for fast growing and excellent meat production performance while maintaining high meat quality has been the major challenge for modern swine selective breeding.The growth rate and meat production performance mainly include body length,backfat thickness,eye area and daily weight gain,and uncovering the genetic mechanism of these traits is helpful to their genetic improvement.In this study,genome-wide association analyses of 20 traits were carried out in five genetic related populations(including Shanxia black pig)using the Chinese Chip-1 Porcine SNP50 K Bead Chip,which was designed and created by our laboratory.Then,haplotypes were constructed by Beagle3.0,and linkage disequilibrium blocks were inferred by Haploview4.2.The functional candidate genes were screened in the linkage disequilibrium blocks,and the effects of few candidate genes were verified in Shanxia black pig.Because the positioning of Shanxia black pig is the first paternal strain in Chinese,this study tested the combining ability and heterosis rate between Shanxia black pig and Duroc(a terminal paternal line)or Lulai black pig(a maternal strain),and provided reference for the industrial application of Shanxia black pig.The results are as follows:(1)Genome-wide association study identified 11 genome-wide loci on nine chromoso-mes and 22 suggestive regions on 15 chromosomes.For the 11 genome-wide loci,eight were detected in at least two populations,and the rest were population-specific and only mapped in Shanxia black pig.After screening the genes within 50 kb of the top SNP for each genome-wide locus,and combining with previous studies,NR6A1 and VRTN were chosen as candidate genes for vertebra number;PLAG1 and BMP2 were identified as candidate genes for body size and backfat thickness;and MC4 R was chosen as a strong candidate gene for body weight.VRTN has effects on thoracic vertebra number,carcass length and body length have been verified in Shanxia black pig.(2)The matching experiment of Shanxia black pig carried out in this project showed that: Shanxia black pig had favorable growth,fattening and body size traits,while Lulai black pig had good reproductive and meat quality traits,and the reciprocal crosses were between them.The reproductive performance of Shanxia black pig × Lulai black pig was better than that of Lulai black pig × Shanxia black pig,but the growth and fertility performance was on the contrary.Because the sows of the four populations were pure breeds,there was no obvious heterosis in reproductive traits.Except fat thickness,eye muscle area and skin thickness having the heterosis,most carcass traits together with meat quality traits had obvious hybrid weaknesses.The heteroses of growth and fattening traits were not consistent in the reciprocal populations,the cross of Lulai black pig × Shanxia black pig showed significant heterosis,while the other cross had no obvious heterosis.The cross of Duroc × Shanxia black pig grows faster and carries more meat than Shanxia black pig,but the meat of quality of the latter is better than the former.Except p H at 45 min and marbling score,all of the meat quality traits of Shanxia black pig are better than or equal to the same trait of the cross.The research of this project shows that: The effects of VRTN have been verified in Shanxia black pig;therefore,it could be used to improve the body size and carcass traits in Shanxia black pig;the cross of Shanxia black pig × Lulai black pig is better than Shanxia black pig in meat quality and reproduction performance,so the cross could be used to product good quality pork;the cross of Duroc × Shanxia black pig products more meat than Shanxia black pig,and also has better economic effect.