Influence of Fat and Carbohydrate Source on Rate of Food Passage of Semipurified Diets for Laying Hens

Abstract

An experiment was conducted with White Leghorn hens to determine the influence of supplemental yellow grease and carbohydrate source on rate of food passage (ROP). Two levels of yellow grease (0 and 7%) and two carbohydrate sources (sucrose and starch) were tested in a complete 2 × 2 arrangement. The ROP was determined by utilizing either Cr2 O3 or 144Ce as nonabsorbable markers. First appearance of the markers in the excreta and percentages of the markers ingested that were recovered in feces 9.5 to 11.5 hr after feeding were criteria used to determine ROP. The ROP varied with the composition of the diet. Diets containing starch had a slower ROP than diets containing sucrose (first appearance time was 156 vs. 127 min, respectively). Also, yellow grease supplementation decreased ROP from 150 to 133 min. The ROP of sucrose-containing diets was decreased more by fat supplementation than the ROP of starch-containing diets (32 vs. 3 min, respectively). Similar trends were observed when ROP was measured as percentage of marker recovered in feces 9.5 to 11.5 hr after feeding. The results show that supplemental fat decreased ROP in chickens. This observation may help in understanding the nature of the extrametabolic or extracaloric effect of fat in poultry diets. With decreased ROP, the diet will be more thoroughly digested and absorbed and, thereby, more energy may be derived from a diet if fat is added than if not.