Abstract
Two digestion trials with two collection periods were conducted to determine the digestibilities of various nutritive components of soybean hulls (mill feed or mill run) by swine. A total of 24 crossbred gestating sows (initial weight 150.5 kg) were used. Hulls were substituted at levels of 7.5, 15 and 30% for a 13% crude protein fortified diet containing 64.4% corn, 20% oats, 5% dehydrated alfalfa meal and 8.4% soybean meal. By analysis, soybean hulls contained (as a percentage of dry matter): 11.8% crude protein, 57.9% cell walls, 42.1% cell content, 43.1% acid detergent fiber (ADF), 38.2% cellulose, 14.7% hemicellulose, 4.8% lignin (KMn04 method) and .11% ADF N. Gross energy of hulls was 4.22 kcal/g. The amino acid content of soybean hulls as a percentage of total amino acids was similar to that reported for soybean meal. As soybean hulls were substituted for the basal diet, digestion coefficients for dry matter, energy, crude protein, cell content and ADF N decreased, while digestion coefficients for cell walls, ADF, cellulose and lignin increased. Hemicellulose digestibility was similar for 0, 7.5 and 15% hulls, but was increased for 30% hulls. The predicted digestibilities for soybean hulls, calculated by difference from the percentage of that nutrient that was from hulls, were: dry matter, 69.4%; energy, 67.4%; crude protein, 47.7%; cell content, 65.0%; cell walls, 72.0%; ADF, 76.9%; hemicellulose, 58.9%; cellulose, 82.1%; lignin, 49.0% and ADF N, -18.6%. The inclusion of soybean hulls in growing and finishing diets was evaluated with 256 crossbred pigs (initial weight was 24 kg) fed fortified corn-dehulled soybean meal diets containing 0, 7.5, 15 and 22.5% hulls. All diets were isonitro-genous and were fed ad libitum. A 16% protein diet was fed to 46 kg, and a 14% diet for the remainder of the test. Average daily gain and daily feed intake did not differ significantly between levels of hulls, although daily gain was reduced when the 22.5% hull diet was fed. Metabolizable energy intake decreased linearly as the level of hulls increased. Feed per unit of gain was greatest for pigs fed the highest level of hulls, with little difference between those fed the other levels. Metabolizable energy per unit of gain favored pigs fed the 15% hull diet. These results suggest that soybean hulls may be used in swine diets at levels up to 15% without adverse effects. Copyright © 1981. American Society of Animal Science . Copyright 1981 by American Society of Animal Science.