GENETIC-PARAMETERS OF PORK QUALITY AND PRODUCTION TRAITS IN YORKSHIREPOPULATIONS

Parameters of pork quality traits and relationships with production tr aits were studied in 7 halothane-negative Dutch Yorkshire populations. (Go) variances due to genotype and batch (day of slaughter) were esti mated using a REML procedure fitting an animal model. High heritabilit ies (0.52 and 0.41) and a rather strong negative genetic relationship (-0.37) were found between carcass lean% and intramuscular fat%. Growt h rate and feed intake showed less important relationships with intram uscular fat% (r(G)'s -0.09 and 0.22, respectively). Traits related to waterholding capacity and colour (pH, drip loss, reflectance, etc.) we re measured at the slaughterhouse as well as in the laboratory. The ge netic variance of these traits was of the same magnitude as the varian ce due to batch effects (about 20%). In a principal Component (PC) ana lysis with 10 quality traits, the first two PCs explained a large prop ortion of the variance (66%). After rotation, these two PCs could be w ell interpreted as representing the DFD or the PSE characteristics. He ritabilities of both PCs were close to 0.20. Genetic relationships bet ween laboratory and slaughterhouse traits (r(G)'s up to -0.79) demonst rated good opportunities for genetic improvement of waterholding capac ity and colour, using relatively inexpensive measurements like pH and reflectance at 45 min and 20 h post mortem. Carcass lean% and growth r ate had no unfavourable correlations with waterholding capacity or col our traits. (Residual) daily feed intake, however, showed moderate to strong associations, especially with colour (r(G)'s up to -0.58), indi cating an increased risk of the DFD aberration in pigs with a high fee d intake and/or indicating a change in muscle fibre type distribution.