Effects of selection on growth, body composition, and food intake in mice: III. Correlated responses:growth, body composition, food intake and efficiency and catabolism

Abstract

SUMMARY: Weekly food intake and body weight were measured from 3 to 17 weeks of age on mice selected 14 generations for increased and decreased values of one of three criteria: appetite (A) as measured by 4- to 6-week food intake, adjusted by phenotypic regression to minimize change in 4-week body weight; fat percentage (F), using the ratio of gonadal fat pad weight to body weight at 10 weeks of age and total lean mass (protein, P), using the index body weight in 10-week males— (8 × gonadal fat pad weight). Carcass composition analyses were undertaken on the 17-week-old mice, and are presented along with composition data for younger mice from earlier generations. The high intake A line mice are larger, eat more, have higher maintenance requirements and are slightly leaner than the low intake A line mice, but are no more efficient. The increased lean mass P line mice are much larger, eat more and are more efficient than the decreased lean mass P line mice, but show little difference in maintenance or carcass composition. The (much) fatter F line mice are larger, more efficient and eat more during the rapid growth period than their leaner F line counterparts, but show no difference in lean mass or maintenance requirements. These results provide implications about the relationships between the input (intake) and output (maintenance and lean and fat deposition) components of growth.