Effect of Overprocessing on Availability of Amino Acids and Energy in Soybean Meal

Abstract

Commercial, dehulled, solvent-extracted soybean meal (DSBM) was overprocessed by autoclaving at 121 C and 105 kPa for 0, 20, 40, or 60 min. Analyzed concentrations (acid hydrolysis followed by ion-exchange chromatography) of lysine and cystine, and to a lesser extent arginine, in DSBM were reduced by increased autoclaving time. Autoclaving time had little or no effect on levels of other amino acids. Performance of chicks fed 40-min autoclaved DSBM as the sole source of dietary protein was inferior to that of chicks fed unautoclaved DSBM. True digestibilities of several amino acids in DSBM decreased (P<.05) as autoclaving time increased, with the largest decreases being observed for lysine, cystine, histidine, and aspartic acid. The effect of autoclaving on lysine was due both to reduced concentration of analyzed lysine and reduced digestibility of the lysine remaining after autoclaving. True digestibilities of most amino acids determined in conventional cockerels were higher (P<.05) than those determined in cecectomized cockerels. Bioavailabilities determined by chick growth assay of lysine in unautoclaved DSBM and DSBM autoclaved for 40 min were 82 and 70%, respectively. Autoclaving had no significant effect on TMEn of DSBM.