GENETIC-PARAMETERS FOR GROWTH-RATE AND BACKFAT IN CANADIAN YORKSHIRE,LANDRACE, DUROC, AND HAMPSHIRE PIGS

Records on 47,360 Yorkshire, 28,762 Landrace, 14,020 Duroc, and 9,983 Hampshire pigs for backfat depth and days to 100 kg made between 1989 and 1992 in herds on the Ontario Swine Improvement Program (OSIP) were used to estimate additive genetic (animal), common environmental (lit ter), and residual variances and covariances of the two traits. Analys is was by the DFREML program of K. Meyer using a multiple-trait indivi dual animal model with fixed effects of genetic groups and herd-year-s eason-sex and random effects of animal, litter, and residual. A comple te relationship matrix was used. Heritabilities were .51, .53, .55, an d .50 for backfat and .31, .30, .26, and .32 for days to 100 kg in Yor kshire, Landrace, Duroc, and Hampshire, respectively. Genetic correlat ions between backfat and days to 100 kg were -.16, -.06, -.17, and -.1 0 for Yorkshire, Landrace, Duroc, and Hampshire. Respective phenotypic correlations were -.08, -.04, -.12, and -.09. Litter effects were lar ge, particularly for days to 100 kg. Resulting common environmental (c (2)) effects were .11, .10, .10, and .11 for backfat and .26, .27, .29 , and .22 for days to 100 kg for Yorkshire, Landrace, Duroc, and Hamps hire. Estimates were highly consistent across breeds and average herit abilities of backfat and days to 100 kg were .52 and .30. Correspondin g average c(2) effects were .10 and .26. Average genetic and phenotypi c correlations between backfat and days to 100 kg were -.13 and -.08.