The apparent and standardized ileal digestibility (AID and SID) of AA and CP and the apparent total tract digestibility (ATTD) of toasted soybean meal (SBM) and untoasted soybean meal (USM) extruded at 86°C (USM86), 120°C (USM120) and 149°C (USM149) were evaluated. USM was extruded mixed with corn starch (396.5g/kg USM and 603.5g/kg corn starch) in a single-screw extruder (MEX 250, Manzoni, Campinas, Brazil). Thirty-six barrows (7.69±0.89 kg BW) were fed a N-free diet, or four diets composed of 30% of each ingredient, as the only source of N, substituting for starch in N-free diet. Pigs were fed at 2.8 x maintenance (2.8 x 106 kcal digestible energy/kg BW0.75) for 10 days (5 d adaptation, 5 d feces collection), and on day 11 piglets were euthanized for ileal digesta collection. A randomized block design was used, with 8 replicates, using the pig as the experimental unit. ANOVA was performed and means were separated using Tukey test (5%). Increasing extrusion temperatures reduced trypsin inhibitors concentrations from 28.24 in USM to 3.51, 1.37, and 1.12 mg/g CP in USM86, USM122, and USM137, respectively, and 2.37 mg/g CP was found in SBM. USM86 showed lower (P < 0.05) ATTD of DM (8-13%), GE (2-4%), and CP (12-16%) compared to SBM, USM120 and USM149, which did not differ (P >0.05). The ATTD of EE of SBM was 17-19% higher (P < 0.05) than of USM86 and USM120, which were similar (P > 0.05) to each other and greater (P < 0.05) than that of USM149. Extrusion at 86°C was insufficient to inactivate anti-nutritional factors and resulted in reductions (P < 0.05) of 25-29% and 27-31% in CP and AA AID and SID compared to SBM, USM120, and USM149, which were, in general, similar (P > 0.05).
Soybean meal extruded at 120° and 139°C presented a similar nutritional value to toasted soybean meal.