Influence of Graded Levels of Fat on Utilization of Pure Carbohydrate by the Laying Hen

An experiment involving 140 SCWL laying hens was conducted to investigate the influence of graded levels of supplemental fat on the nitrogen-corrected metabolizable energy (ME) of diets containing different carbohydrates. Twenty-four diets with the same ME: protein ratio were arranged in a 4 × 6 factorial composed of four levels of yellow grease (0, 3, 6 and 9%) and six carbohydrate sources (sucrose, starch, maltose, glucose, fructose, and glucose + fructose). Four additional diets in which the specific carbohydrate was not included, were formulated to facilitate the determination of the MEn of the carbohydrates. The ME of each carbohydrate increased with each increment of supplemental fat. When yellow grease constituted 0 or 9% of the diet, the respective ME values of the carbohydrates (kcal/kg), expressed in a relative index form with the ME of sucrose in diets without added fat set equal to 100, were 100 and 110 for sucrose, 96 and 103 for starch, 93 and 100 for maltose, 92 and 101 for glucose, 90 and 98 for fructose and 89 and 98 for the glucose + fructose mixture. The data indicate that supplemental fat enhanced the utilization of energy from nonlipid dietary constituents. The mechanism by which fat exerts this influence on utilization of dietary energy is not known, but the possible relationship between decreased rate of food passage resulting from supplemental fat and energy utilization is discussed.