Growth and Food Consumption in Relation to Dietary Levels of Protein and Fibrous Bulk

Abstract

Diets containing varying dietary levels of protein, cellu flour (wood-pulp cellulose) and glucose were employed to study their effects on the ad libitum food consumption and growth of 9-day-old chicks maintained for a 20-day experimental period. In one experiment, 4 protein levels (5.3, 10.7, 16.0 and 21.3%) were fed at each of 5 levels of cellu flour (0, 12, 24, 36 and 48%). Food consumption (and as a result of this, growth rate) was stimulated by replacing glucose with moderate amounts of cellu flour. Food intake increased to satisfy the energy needs; as a result, the protein intake also increased and more rapid growth resulted. At very high cellu flour levels the energy level was low and not enough food could be consumed to satisfy the need for energy. At the lower levels of cellu flour the growth rate was determined by protein intake. Growth could be increased either by raising the protein level of the diet or by decreasing the density of calculated metabolizable energy in the food (i.e., by increasing the bulk), which by increasing the food consumption resulted in an increased protein intake. At higher levels of bulk, the volume of food consumed was high but the growth rate was limited by an energy deficiency caused by the low energy level of the diet. Criteria of food utilization were also compared. With diets containing high levels of cellu flour, weight gain ÷ food consumed was not a satisfactory measure of food utilization. Estimation of nutrients consumed by subtraction of cellu flour content from food consumed allowed calculation of a ratio of gain in weight to energy consumed that was about constant for each protein level. Low protein diets produced carcasses of high fat content. Addition of cellu flour to the diet decreased the fat content. Levulinic acid and calcium gluconate, substances which have been observed by some investigators to stimulate growth, were without effect with these diets.