ANALYSIS OF PIG CHROMOSOME-7 GENETIC-MARKERS FOR GROWTH AND CARCASS PERFORMANCE TRAITS

The successful identification and mapping of a large number of genes a nd anonymous genetic markers have made it possible to identify quantit ative trait loci (QTL) in the pig. Previous research, both in our labo ratory and other laboratories, had identified the association of the s wine major histocompatibility complex (SLA) with birth weight, weanin g weight, growth rate, and backfat. The purpose of this project was to further investigate these past associations. Using our ISU reference families consisting of crosses of the Chinese breeds, Meishan and Minz hu, with the US breeds, Duroc, Landrace, and Hampshire, the associatio n of five chromosome 7 genetic markers with birth weight, weaning weig ht, average daily gain, backfat, loin eye size, colour, marbling, and firmness was examined. The genetic markers along chromosome 7 were S00 64, TNF alpha, S0102, S0066, and S0101, and they spanned approximately 90 centimorgans of chromosome 7. There were two alleles for TNF alpha and from four to 13 alleles for the microsacellites' markers. Gene-su bstitution models were used to analyse the data. Results demonstrated that a QTL for birth weight is located near the SLA complex. Using all the data combined, TNF alpha (p < 0.05) and S0102 (p ( 0.01) alleles were associated with differences in level of backfat. In some families other markers were significantly associated with average daily gain a nd loin eye area. These results demonstrate the care that is needed in interpreting possible QTL effects when several traits and markers are used.