ILEAL DIGESTIBILITIES AND URINARY LOSSES OF AMINO-ACIDS IN PIGS FED HEAT-PROCESSED SOYBEAN PRODUCTS

Twelve crossbred gilts fitted with simple T-cannulas at the distal ile um were fed four soybean products in a replicated 4 x 4 Latin square, Treatments were soybean meal (SBM), extruded (Ex), full-fat soybeans ( FFSB), roasted FFSB processed under normal conditions (RoN) and under conditions used to increase rumen bypass protein (RoB). The recovery o f endogenous lysine at the distal ileum was determined with the homoar ginine technique. Apparent ileal digestibilities of crude protein (CP) and all essential amino acids, with the exception of isoleucine and l ysine, were higher (P < 0.001) in SBM as compared to extruded FFSB but digestibilities in the latter were superior (P < 0.001) to those in e ither form of roasted FFSB. Apparent ileal digestibilities of isoleuci ne and lysine and true digestibility of lysine were similar (P > 0.05) in SBM and extruded FFSB, but lower (P < 0.001) in either form of roa sted EFSB. When compared to pigs fed extruded FFSB or SBM feeding eith er form of roasted FFSB resulted in a higher (P < 0.001) endogenous as well as exogenous flow of lysine. Compared to feeding any other soybe an product, RoB FFSB increased (P < 0.05) urinary losses of lysine whe n expressed as a percentage of ileal digestible lysine. The present st udy demonstrated that reductions in apparent ileal lysine digestibilit ies resulted from higher recoveries of endogenous as well as exogenous lysine.