Nutrient digestibility in food waste ingredients for Pekin and Muscovy ducks

Food wastes are valuable resources to be recycled into new added-value products through animal production. The determination of energy and digestibility values of these wastes is essential for feed formulation. Corn, soybean meal (SBM), and a total of nine industrial food waste ingredients were tested in a comparative metabolic study in Pekin and Muscovy ducklings at two different ages during growth. The "precision-feeding" technique was employed to establish DM, fat, and fiber digestibility as well as retention of N and energy (AME, AMEn in Pekins; and AME, AMEn, TME, TMEn in Muscovies) for the 11 ingredients. For Pekin at 3 wk of age, the AMEn of peanuts, tofu, pogo, granola, waste diet, bread, corn, SBM, okara, and brewers grains were 5,141, 4,019, 3,971, 3,908, 3,141, 2,279, 1,572, and 1,442 kcal/kg, respectively. For Pekin at 6 wk of age, the AMEn of peanuts, pogo, tofu, granola, waste diet, bread, corn, SBM, and okara were 5,340, 4,327, 4,254, 4,079, 3,567, 3,302, 3,201, 2,416, and 1,562 kcal/kg, respectively. For Muscovy at 7 wk of age, the TMEn of peanuts, pogo, granola, waste diet, corn, tofu, bread, SBM, okara, and peanut skin were 5,207, 4,321, 4,057, 3,733, 3,233, 3,180, 3,084, 2,236, 1,575, and 904 kcal/kg, respectively. For Muscovy at 11 wk of age, the TMEn of peanuts, pogo, granola, tofu, waste diet, corn, bread, SBM, okara, and brewers grains were 5,077, 4,137, 4,025, 3,921, 3,586, 3,254, 3,123, 2,245, 2,007, and 1,392 kcal/kg, respectively. Nitrogen retention was significantly (P < 0.05) higher for SBM, tofu, okara, pogo, peanuts, and the food waste diet and lower for bread, corn, granola, brewers grains, and peanut skin. Dry matter digestibility was high for granola, pogo, corn, bread, and the food waste diet. Fat digestibility was generally the same for all the ingredients and was consistently over 97%. Bread neutral detergent fiber (NDF) was significantly (P < 0.05) the most digestible (88.92% NDF digestibility), as it consisted of 96.29% hemicellulose, whereas okara NDF was significantly (P < 0.05) the least digestible (26.94% NDF digestibility) and contained only 14.38% hemicellulose. Peanut skins and SBM with 30% hemicellulose showed only slightly higher digestibilities of NDF. The results of this study establish reliable data for formulation of duck diets using the tested industrial food waste ingredients as well as corn and SBM in both Pekin and Muscovy ducklings at two different ages during growth to market weight.