REALIZED HERITABILITY ESTIMATES IN BOARS DIVERGENTLY SELECTED FOR TESTOSTERONE LEVELS

Data were collected from 1982 through 1992 from 100 sires and 891 Duro c boars. Testosterone production was measured from peripheral blood sa mples before (PRE) and after (POST) GnRH challenge. Additionally, data were collected on testes volume at 168 d (TVOL), days to 104 kg (DAYS 104), number born alive (NBA) and backfat adjusted to 104 kg body weig ht (FAT). Realized heritabilities were estimated from the regression o f response on cumulative selection differentials. Heritabilities for P OST were .15 +/- .18 and .24 +/- .08 in the low and high lines, respec tively. This compares with the estimate of .26 +/- .21 from son-sire r egressions. The regression of other traits on cumulative selection dif ferentials can be viewed as realized correlated responses to selection . After 10 generations, the high line was approximately three times gr eater 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.