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Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/15/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Typically, the three factors affecting a market hog's value are fatness, musculature and dressing percentage. Studies have been reported which identified regions of the genome which affect fat deposition in pigs; however, no studies have been conducted for measures of musculature or dressing percentage. Therefore, we decided to study these economically important traits in the MARC swine resource population of Meishan x White composite pigs. In addition, measures of trimmed wholesale product yield and carcass length were evaluated. Significant associations with trimmed wholesale product yield were detected on chromosome 1 and X. Loineye area was also associated with chromosome 1. A region on chromosome 7 was associated with carcass length and dressing percentage. Each of these chromosomal regions were significantly associated with backfat depth in a different study indicating that the genes detected may affect more than one trait. Our understanding of the inheritance of musculature and trimmed wholesale product yield has been enhanced by the results of this study. Identification of different traits also affected by these chromosomal regions will help determine the biological processes altered by the gene causing the observed effect. Further testing of these regions in other populations to characterize allelic variation is warranted to determine their utility for marker assisted selection to improve carcass composition. Technical Abstract: A genomic scan was conducted on 540 reciprocal backcross Meishan by White composite pigs for hot carcass weight (HCWT), loineye area (LOIN), carcass length (CRCL), belly weight (BELLY) and weight of trimmed ham, loin, picnic and boston butt adjusted to a constant live (TWPLWT) or carcass (TWPCWT) weight. Genetic markers spanned the entire porcine linkage map and were spaced at interval less than 20 cM when possible. Grandparental breed of origin for all chromosomal segments was determined using multipoint linkage procedures and a least-squares regression analysis was conducted. Nominal p-values were converted to a genome wide level of significance to adjust for the numerous number of tests actually conducted. A total of seven associations were significant at the genome-wide level relating to chromosomes 1 (SSC 1), 7 (SSC 7) and X (SSC X). SSC 1 affected LOIN, TWPLWT and TWPCWT, SSC 7 affected HWCT and CRCL and SSC X affected TWPLWT and TWPCWT. Seventeen associations relating to 8 chromosomal regions (including SSC 1 and X) presented suggestive evidence for QTL and many of these regions are likely to contain QTL. Chromosomes 8 and 14 had 4 and 3 traits with suggestive evidence for QTL, respectively. Many pleiotropic effects were detected for regions on SSC 1, 7, 14 and X in this study and a previous study looking for fat deposition QTL in the same population. In addition, SSC 4 was nearly significant for CRCL in the same region identified as affecting backfat in a wild boar by Large White population. These results expand our knowledge of the inheritance of quantitative traits and will be directly relevant to composite populations containing Meishan germplasm. |
