Influence of Processing Method on Ileal Digestibility of Nutrients from Soybeans in Growing and Finishing Pigs

Abstract

Eight crossbred barrows (four growing and four finishing pigs with average initial BW of 40 and 82 kg, respectively) were fitted with T-cannulas at the distal ileum and used in a 36 d metabolism experiment (4 × 4 Latin squares) to determine the effects of roasting and extruding full-fat soybeans on nutrient utilization. Treatments were: 1) soybean meal; 2) roasted soybeans; 3) extruded soybeans; and 4) soybeans extruded with an extrusion enhancer (sodium sulfite). The control diet was corn starch-based with 0.90% lysine, 0.65% Ca and 0.55% P for the growing pigs and 0.75% lysine, 0.55% Ca and 0.45% P for the finishing pigs. For the growing pigs, apparent total tract digestibilities of DM (p<0.04) and GE (p<0.008) were greater for soybean meal than full-fat soy products. However, ileal digestibilities of DM, GE, N and most amino acids were, in general, greatest for extruded soybeans and lowest for roasted soybeans, with soybean meal intermediate. For finishing pigs, trends in digestibilities of nutrients were very similar to those for the growing pigs. Total tract digestibilities of DM (p<0.03) and GE (p<0.001) for soybean meal were greater than for the full-fat soy products and ileal digestibilities of DM, GE, N and most amino acids were greater for the extruded soybeans than for the roasted soybeans. In conclusion, nutrient digestibilities and availabilities of indispensable amino acids tended to be greatest in extruded soybeans, intermediate in soybean meal and lowest in roasted soybeans for growing and finishing pigs.