Two series of experiments were performed to determine the effect of an indigestible substance (silica gel) and of dietary fiber, supplied by dehydrated alfalfa meal, on the amount of fecal metabolic energy (FMe) and endogenous urinary energy (UEe) excreted by roosters and laying hens. A third series of experiments was performed to measure the additivity of independently determined true metabolizable energies of specific feed ingredients for laying hens;In the first series (3 experiments), the energy excreted by roosters that were force-fed silica gel (SG), corn or SG-corn mixtures was determined and these data were used to calculate the true metabolizable energy (TME) of corn. The regression coefficient, obtained from multiple regression analysis, indicated that each gram of SG caused the excretion of an extra .47 kcal of FMe+UEe per rooster in 24 hr. The TME of corn was 4.05 kcal per g dry matter when the corn was force-fed alone. The energy excreted by roosters force-fed SG-corn mixtures was corrected for the effect of SG on FMe and UEe excretion. The average corrected TME of corn was 3.97 per g dry matter when this grain was fed in combination with SG;In the second series of experiments, the FMe+UEe energy excreted by pullets fed diets containing 2.70, 3.40, 4.10, 5.00 and 5.70% dietary acid detergent fiber (ADF) were determined. Dehydrated alfalfa meal was used to achieve the dietary ADF levels. The average FMe+UEe energy values among diet treatments and across trials varied from 5.79 to 7.25 kcal per kg body weight during this period. Dietary ADF had no significant effect (P > .05) on FMe+UEe energy excretions and the amounts of FMe+UEe were not related to body weight of pullets;In a third series of experiments, the TME values of seven feedstuffs corn, soybean meal (SBM), animal-vegetable fat blend (A-Vfat), wheat shorts, meat and bone meal (MBM), dehydrated alfalfa meal, and hydrolyzed feather meal (HFM) and selected mixtures prepared therefrom were determined by using laying hens. TMEs of ingredient mixtures determined experimentally (observed TMEs) were compared with those expected on the basis of the additive contribution of individual TMEs of each ingredient in the mixture. The results showed that in most instances, the observed TMEs of mixtures of corn and SBM, wheat shorts and MBM, and dehydrated alfalfa meal and HFM did not differ significantly from expected TMEs.