ENDOGENOUS RECOVERIES AND TRUE ILEAL DIGESTIBILITIES OF AMINO-ACIDS IN NEWLY WEANED PIGS FED DIETS WITH PROTEASE-TREATED SOYBEAN-MEAL

Endogenous recoveries and true ileal digestibilities of amino acids we re determined in pigs fed cornstarch-based diets with untreated or pro tease-treated soybean meal. as protein sources. Twelve pigs, fitted wi th a modified post valve T-cecum cannula on d 14, 15, and 16 after bir th, were weaned on d 20 and assigned to one of four diets according to a two-period balanced change-over design. Diets consisted of soybean meal a) untreated (SBM), 2) incubated (1:2 wt/vol in distilled water a djusted to pH 4.5, for 16 h at 50 degrees C; CI-SBM), 3) sprayed with protease (1 mu L/g of soybean meal; PS-SBM), and 4) incubated, as far CI-SBM, with protease in the water (PI-SBM) at the same application ra te as that for PS-SBM. Each period consisted of 5 d of adaptation to d iets followed by collection of ileal digesta on d 6 and 7 to determine the apparent ileal amino acid digestibilities of the diets. On d 9, g uanidinated meals were fed, followed by a 24-h continuous collection o f digesta. Recoveries of chromic oxide and dysprosium from the guanidi nated meals were 96.0 +/- .5 and 94.5 +/- 1.1%, respectively. Endogeno us amino acid recoveries were similar (P > .05) for SBM, CI-SBM, and P S-SBM but less(P < .05) for PI-SBM. True digestibilities were also les s (P < .05) for PI-SBM than for the other meals. Recoveries of endogen ous branched-chain and aromatic amino acids were less (P < .05) during Period 2 than during Period 1, suggesting dietary change-and(or) age- dependent adaptive increases in the secretions of pepsin and pancreati c proteases. In conclusion, protease treatment did not improve the tru e digestibilities of amino acids in soybean meal fed to newly weaned p igs.