Effects of dietary protein level on growth and body composition in mice divergently selected for fat content

Abstract

A study was conducted to examine the effects of dietary protein percentage and selection for divergence in fat content on growth and body composition in mice. The three lines used had been selected as follows: high epididymal fat pad weight as a percentage of body weight (HF), low epididymal fat pad weight as a percentage of body weight (LF) and a randomly selected control (RC). Mice from each line were allotted at weaning (3 wk of age) to one of four dietary protein percentages: 12, 16, 20, and 24%. Growth and efficiency of feed conversion were measured at 2-wk intervals and mice were killed and body composition was measured at 9-wk of age. Overall, HF mice grew faster were more efficient at converting feed to body weight gain, and had empty carcasses with a higher percentage of tat (P < 0.05) and a lower percentage of protein than LF mice. However, fat-free empty-body protein and ash percentages, protein gain, protein gain:protein intake, and protein gain:energy intake ratios were not different among genotypes. As dietary protein percentage increased, gain:feed ratio increased quadratically (P < 0.05) in all genotypes and was maximized m mice consuming 16% protein. Protein gain was maximized in mice consuming 16% protein. Feeding diets providing protein percentages above or below 16% depressed protein gain and protein gain:energy intake ratio. Genetic line-by-dietary-protein-level interactions were generally not significant for growth, feed efficiency and body composition traits. Key words: Mice, dietary protein, growth, body composition, fat deposition