REALIZED HERITABILITY ESTIMATES IN BOARS DIVERGENTLY SELECTED FOR TESTOSTERONE LEVELS

Data were collected from 1982 through 1992 from 100 sires and 891 Duroc boars. Testosterone production was measured from peripheral blood samples before (PRE) and after (POST) GnRH challenge. Additionally, data were collected on testes volume at 168 d (TVOL), days to 104 kg (DAYS104), number born alive (NBA) and backfat adjusted to 104 kg body weight (FAT). Realized heritabilities were estimated from the regression of response on cumulative selection differentials. Heritabilities for POST were .15 +/- .18 and .24 +/- .08 in the low and high lines, respectively. This compares with the estimate of .26 +/- .21 from son-sire regressions. The regression of other traits on cumulative selection differentials can be viewed as realized correlated responses to selection. After 10 generations, the high line was approximately three times greater than the low line for both PRE and POST levels of testosterone. Although not significant, high line pigs required fewer days to reach 104 kg, had more backfat and larger testes than low line pigs. Litter size was significantly larger for high line than for low line.