The effect of varying steam conditioning temperature and time on pellet manufacture variables, true amino acid digestibility, and feed enzyme recovery

Increasing conditioning temperature and conditioning time has been considered a feed manufacture strategy to improve feed hygienics that may also affect feed production and nutritional quality. The objective of the study was to assess how varying steam conditioning temperatures and conditioning times interacted to affect pellet manufacture variables, true amino acid digestibility, and exogenous mixer-added enzyme recovery. Corn and SBM diets that included dried distillers ' grains with solubles and meat and bone meal were conditioned at either 77 degrees C, or 82 degrees C, or 88 degrees C with conditioning times of either 30 or 60 s. Treatments were arranged in a three (steam conditioning temperature) X 2 (conditioning time) factorial in a randomized complete block design. Digestible amino acid concentration was estimated using cecectomized roosters in a Latin Square with crossover design. Motor load decreased for 30-s conditioning compared to 60-s conditioning when diets were subjected to 77 degrees C and 82 degrees C, but the time effect was lost at 88 degrees C. Pellet quality increased incrementally with increased steam conditioning temperature (P < 0.05). Exogenous mixer-added enzyme ac-tivity decreased at 88 degrees C (P = 0.0001) and was not significantly affected by conditioning time. Conditioning temperature and time interacted to influence digestible amino acid con-centrations of methionine, lysine, threonine, alanine, aspartic acid, glutamic acid, isoleucine, leucine, proline, and valine (P < 0.05). Higher temperatures at 30-s conditioning increased digestible amino acid concentrations; however, conditioning at the highest 88 degrees C for 60 s decreased concentrations. These data demonstrate bene fits of increased temperature and time conditioning to a threshold where enzyme activity and digestible amino acid concentration decreased.