Line characterization and evaluation of genetic parameters of serum cholesterol levels, activity, feed intake, growth and body moisture in selected and unselected lines of laboratory mice
Feed intake, growth, efficiency, and serum cholesterol levels (SCL) were recorded for 102 male mice, and voluntary physical activity and SCL were recorded for 113 male mice from lines selected for 22 generations for maximum 21- to 42-day gain (H), minimum 21- to 42-day gain (L), and a random-bred control (C). Heritability (h²), phenotypic and genetic correlations of SCL, activity, growth, and body moisture content were estimated for 466 sire-son pairs of mice from an unselected line. Blood samples were obtained by sinus orbital bleeding at 35 and 70 days of age in the line characterization study and at 62 days of age in the genetic parameters study and were analyzed for SCL by gas chromatography. Voluntary physical activity was recorded as revolutions of an exercise wheel every sixth day from 21 to 70 days of age in the line characterization study and at 28, 49, and 70 days of age in the genetic parameters study. Feed intake (of an 11% fat, 9% fat, and 4-1/2% fat diet) was recorded for several days each week and extrapolated to obtain weekly intake data. A least-squares analysis of variance from a model including lines, diets, and line x diet interactions indicated highly significant differences in the main effects but few significant interactions. Total SCL, growth, and efficiency were higher, and intake lower in mice on the higher fat diet. SCL (mg/100 ml) at 10 weeks of age was 220.3, 178.1, and 180.4 for animals fed an 11% fat diet and 143.3, 124.1, and 132.2 for animals fed a 4.5% fat diet. Activity scores (revolutions) for the H, C, and L lines were 79234, 107987, and 124409. Activity generally increased in all lines from 21 to 56 days of age, then declined slightly. Heritability estimates of SCL and body moisture 2 content were .31 ± .07 and .20 ± .11, and h² estimates for activity ranged from .27 ± .14 to .54 ± .12. Negative genetic correlations occurred between body moisture content and SCL and between body moisture content and weight gains.