Guanidinated protein test meals with higher concentration of soybean trypsin inhibitors increase ileal recoveries of endogenous amino acids in pigs

The amino acid concentrations of cornstarch-based guanidinated unprocessed (UGM) and autoclaved (AGM) Nutrisoy (defatted soy flour) protein test meals were compared with the respective unguanidinated Nutrisoy diets. Endogenous ileal recoveries and true digestibilities of amino acids were determined in six growing pigs, fitted with a simple T-cannula at the distal ileum, fed the guanidinated protein test meals. The UGM and AGM contained 13.4 (high) and 3.0 (low) g/kg dry matter of soybean trypsin inhibitors (SBTI), respectively. The experiment was a two-period cross-over design with each period lasting 15 d. On d 14 of each period, the pigs were fed the guanidinated test meals followed by 24 h continuous collection of digesta. Concentrations of crude protein and most of the amino acids in the test meals were higher than in the respective diets. Apparent ileal amino acid digestibilities of the test meals did not differ (P > 0.05) from reported values for the respective diets and were higher (P < 0.05) by 22.7 (cysteine) to 61.3 (tyrosine) percentage units for AGM compared with UGM. The ileal recoveries of endogenous amino acids in AGM-fed pigs were lower (P < 0.05) than UGM-fed pigs. Values ranged from -0.10 (arginine) to 0.64 (aspartate + asparagine) and from 0.84 (histidine) to 2.61 (tyrosine) g/kg dry matter intake for AGM-and UGM-fed pigs, respectively. True ileal amino acid digestibilities for AGM were higher (P < 0.05) than UGM with differences ranging from 12.7 (tyrosine) to 38.3 (leucine) percentage units. In conclusion, ileal recoveries of endogenous amino acids were increased in pigs fed guanidinated protein test meals with the higher concentration of SBTI.