Selection for components related to body composition in mice: direct responses.

Replicated within full-sib family single-trait selection was conducted for 10 generations in mice for (1) high or low 12-week epididymal fat pad percentage (100 x epididymal fat pad weight/body weight) or (2) high or low 12-week hind carcass percentage (100 x hind carcass weight/body weight). Pooled realized heritabilities based on high, low and divergent selection were 0.66±0.09, 0.65±0.13 and 0.66±0.05 for epididymal fat pad percentage and 0.48±0.08, 0.33±0.08 and 0.40±0.04 for hind carcass percentage. The pooled realized genetic correlation (rG R) between epididymal fat pad percentage and hind carcass percentage based on divergence was -0.67±0.04. Other estimates of (rG R) were: epididymal fat pad percentage with body weight (0.57±0.05); epididymal fat pad percentage with epididymal fat pad weight (1.17±0.05); hind carcass percentage with body weight (-0.61±0.09); hind carcass percentage with hind carcass weight (-0.05±0.11). Indirect measures of fat and lean tissue percentages were highly heritable, and (rG R) between them would be desirable from the standpoint of analogous types of traits in livestock. In the same context, undesirable (rG R)'s were found between epididymal fat pad percentage and body weight and between hind carcass percentage and body weight.