Heterotic and maternal effects on body composition of LL and SS rats and their reciprocals at two ages.

A diallel cross between two genetically similar growth strain lines of rats, varying greatly in body size was made in order to evaluate the differences in carcass composition at 15 and 25 weeks of age. Traits assessed were percentages of dry matter, ash, fat, and protein of empty body weight. Analysis of variance of the components in the model indicated no significant differences in carcass constituents at age 15 weeks except dry matter. Rat carcasses at 25 weeks of age showed an increase in fat per cent (p less than .05) from 15 to 25 weeks of age. A significant maternal influence was expressed for fat per cent in favor of the LL dam and for protein per cent favoring the SS female. Heterosis was more evident (p less than .05) at 25 weeks than 15 weeks for ash, fat, and protein percentages.