True metabolizable energy (TME) bioassays of waterfowl foods typically use birds not provided with grit, and foods are fed in an intact, natural state. To determine if the use of grit-free birds provides accurate estimates of the TME of intact foods, we fed corn (Zea mays), milo (Sorghum vulgare), wild millet (Echinochloa crusgalli), and largeseed smartweed (Polygonum pensylvanicum) to giant Canada geese (Branta canadensis maxima) supplied with grit ad libitum and denied grit for the duration of TME bioassays. In a second experiment, the 4 test foods were ground and fed to grit-free geese to determine if this procedure provides results that approximate the energy extracted from intact foods by geese having access to grit. For TME bioassays of intact foods, we detected no difference in the ability of the 2 groups of geese to digest either corn (P = 0.064) or millet (P = 0.606); however, grit-free birds digested smartweed (P < 0.001) and milo (P < 0.034) more efficiently than geese supplied with grit. We attribute the results for smartweed and milo to the retention of these food items in the gizzards of grit-free geese, because birds frequently substitute hard seeds for grit when mineral particles are unavailable. In the second experiment, grit-free geese digested smartweed (P < 0.001) and milo (P = 0.037) more efficiently than geese supplied with grit and fed these 2 foods intact. Grit-free geese also digested ground millet more efficiently than geese provided with grit and fed millet intact, however, this difference was only marginally significant (P = 0.056). Corn was digested more efficiently when fed intact to geese supplied with grit, (P = 0.027), although the difference in digestive efficiency was less than 5% between these 2 treatments. Feeding birds ground food appears to overestimate TME for some foods because grinding may eliminate the fraction of food that normally passes through the digestive tract intact. We recommend researchers provide experimental birds with grit and feed foods intact for accurate estimates of TME.