Effect of varying ratios of fat and protein in fiber-free semisynthetic diets on fecal output of pig-tailed monkeys (Macaca nemestrina)

Abstract

The effect of varying the ratios of dietary fat, protein and carbohydrate on the amount and composition of fecal output was studied in adult, male pig-tailed monkeys (Macaca nemestrina) fed liquid, fiber-free semisynthetic diets. The dietary nitrogen was supplied as an enzymatic protein hydrolyzate (biological value = 86%), the fat as corn oil, and the carbohydrate as corn syrup solids. Vitamins and minerals were added to meet the nutritional requirements of this monkey. Nine diets were fed for 2 weeks, and fecal excreta collected daily after 4-day adaptation to a new diet. The levels of protein/day were 40, 80, and 160 kcal/animal and the levels of fat/day were 4.5, 22.5, and 112.5 kcal/animal. Carbohydrates were adjusted to maintain the diets isocaloric (700 kcal/day per monkey). The assumption was made that a) there was no time trend, and b) that the preceding diet had no carry-over effect on the next diet being tested. Results suggest that total fecal output was greater on the high protein diets, especially when fat levels were either 4.5 or 112.5 kcal. The 22.5 kcal fat and 160 kcal protein did not show an increase in fecal output. These fecal output differences were related to changes in fecal moisture but not in dry fecal matter. Increased nitrogen loss in the feces was noted for all 160 kcal protein diets, and especially so when the fat level was 4.5 kcal. The 112.5 kcal fat diet produced feces higher in total lipids. If a fiber-free formula diet is designed to induce a minimum of fecal bulk, the most satisfactory formulation appears to be one with a moderate amount of dietary fat, and a protein content in the general range of the recommended daily allowance.