Organ and skeletal growth in mice with a major gene for rapid postweaning growth

Growth of liver, heart, kidney and femur in mice with a major gene for rapid postweaning growth (hg/hg, line Ch) was compared to that of their normal controls (Hg/-, line CH). Male mice of both lines were sacrificed at 7 day intervals from 21 to 56 days of age. By day 56 mice of line Ch weighed 40.1 g and individuals of line CH weighed 30.2 g. At sacrifice, individuals were weighed, the naso-anal length and tail length measured and the liver, heart and kidney were removed and weighed. The left femur was also removed and its length measured. Significant differences between lines were detected for all traits observed when examined on an uncorrected basis. This significance disappeared when organ weights were adjusted by body weight at sacrifice through covariance analysis. Similarly, there was no significant in femur length across lines when bone lengths were adjusted for naso-anal length. Only differences in tail length remained significant after adjustment for body length. These results suggest that the impact of the hg allele is of a fundamental and general nature, with little impact on specific tissues or functions of growth.