Nutrient Digestibility of Soybean Meal Products Based on In Vitro Procedures for Pigs

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The present work aimed to assess the nutrient digestibility of soybean meal (SBM) products based on in vitro procedures. Two-step and three-step in vitro assays were performed to mimic the digestion and absorption of nutrients in the digestive tracts of growing swine. The two-step in vitro method was modified to reflect the digesta retention time and digestive enzymes of nursery piglets by decreasing incubation periods and digestive enzymes to half of those in the procedure for growing pigs and was used to determine the crude protein (CP) digestibility of nursery piglets. The seven ingredients included conventional SBM, thermo-mechanically processed SBM (TSBM), and five sources of fermented SBM (FSBM). The five sources of FSBM were produced using different microorganisms for fermentation, namely: (1) Pediococcus pentosaceus and Bacillus subtilis, (2) Enterococcus faecium (FSBM-EF), (3) Aspergillus oryzae and Bacillus subtilis, (4) Aspergillus oryzae, and (5) Bacillus licheniformis. Based on the conventional procedure, the in vitro ileal disappearance of CP in TSBM was greater (p < 0.05) compared with that in FSBM sources. Based on the in vitro assays for total tract digestibility, organic matter in TSBM was better digested (p < 0.05) compared with that in FSBM except for FSBM-EF. Based on the in vitro procedure for nursery piglets, the ileal disappearance of CP in TSBM was greater (p < 0.05) than that in the other SBM products. Taken together, thermo-mechanical processing rather than microbial fermentation of SBM improves the nutrient digestibility of SBM, particularly in nursery pigs.