Genome-wide Association Study Of Back Fat Thicknesses At Four Locations On Carcass In Laiwu And Erhuaiian Populations

Backfat thickness is an index to reflecting the fat deposit ability and is also a measurement of lean meat rate. Therefore, decoding the genetic architecture of backfat thickness has economic importance. Backfat is different between foreign commercial breeds and Chinese native breeds. Large White, Landrace, Duroc and so on are lean pigs with thin backfat, while Laiwu, Erhualian and other Chinese native breeds belong to lard-type pigs with thick backfat. With the development of biological technology and application of the pig 60 K SNP chip, the researchers have identified a lot of QTLs, SNPs and candidate genes for the backfat thickness. However, most of the researches have focused on resource populations or commercial breeds, and few studies have performed in Chinese local breeds.This study measured the backfat thicknesses at shoulder, 6-7 rib, waist and hip in 316 Laiwu pigs and 334 Erhualian pigs. All of the backfats in two populations are thicker than 25 mm, and the backfats at shoulder and waist are the thickest and thinnest. All of the backfats are higher in Laiwu pigs than in Erhualian pigs. There is no difference between sexes in Laiwu population, but castrated males’ backfat is thicker than intact females. The correlation coefficients between backfat and the weights of abdominal, leaf and veil fats are significantly positive. The correlation coefficient between average backfat and the backfat at 6-7 rib is strongest(r ≥ 0.9) in both populations. Then, we used the porcine 60 K SNP chip to genotype the 650 animals, and genome-wide association analyses were performed separately and jointly. Two regions, each on chromosome 4 and 7, were detected in Erhualian pigs. One and two SNPs were associated with backfat on SSC11 and SSC12 respectively in the Laiwu population. Four loci were identified by the meta analysis, which locate on SSC4, 7, 12 and X respectively. As expected, the meta analysis has more power. It not only detected all of the loci except one on SSC11, but also identified a new locus on SSCX. These findings consistent with previous reports, and paved the basis for further study.