ESTIMATION OF DOMINANCE VARIANCE IN PUREBRED YORKSHIRE SWINE

We used 179,485 Yorkshire reproductive and 239,354 Yorkshire growth re cords to estimate additive and dominance variances by Method Fraktur R . Estimates were obtained for number born alive (NBA), 21-d litter wei ght (LWT), days to 104.5 kg (DAYS), and backfat at 104.5 kg (BF). The single-trait models for NBA and LWT included the fixed effects of cont emporary group and regression on inbreeding percentage and the random effects mate within contemporary group, animal permanent environment, animal additive, and parental dominance. The single-trait models for D AYS and BF included the fixed effects of contemporary group, sex, and regression on inbreeding percentage and the random effects litter of b irth, dam permanent environment, animal additive, and parental dominan ce. Final estimates were obtained from six samples for each trait. Reg ression coefficients for 10% inbreeding were found to be -.23 for NBA, -.52 kg for LWT, 2.1 d for DAYS, and 0 mm for BF. Estimates of additi ve and dominance variances expressed as a percentage of phenotypic var iances were, respectively, 8.8 +/- .5 and 2.2 +/- .7 for NBA, 8.1 +/- 1.1 and 6.3 +/- .9 for LWT, 33.2 +/- .4 and 10.3 +/- 1.5 for DAYS, and 43.6 +/- .9 and 4.8 +/- .7 for BF. The ratio of dominance to additive variances ranged from .78 to .11.