Further processing of soybean meal using thermomechanical and enzyme-facilitation modified secondary protein...

Further processing of protein feedstuffs, such as conventional soybean meal (CSBM), may improve their nutritive value. This study evaluated chemical attributes, in-vitro protein digestion kinetics, apparent (AID) and standardized (SID) ileal digestibility of amino acids (AA), and apparent metabolizable energy (AME) in CSBM subjected to thermomechanical and enzyme-facilitated processing (PSBM). For the in vitro digestion, samples were sequentially incubated in triplicate, with pepsin at pH 2.5 for 0 and 0.5 h (gizzard phase), then with pancreatin and bile extract for 0, 0.5, 1, 1.5, 2, 2.5 and 3 h (intestinal phase, pH 6.5). A total of 180 one-day-old Ross 708 male chicks were fed a commercial starter diet until day 13 (n = 6). On day 14, birds were assigned to one of three diets: a nitrogen-free diet (NFD), or test ingredients containing 20 % crude protein (CP) from either CSBM or PSBM as the sole source of AA. Titanium dioxide (0.5 %) was included as an indigestible marker. Excreta were collected between days 17 and 20, and ileal digesta on day 21. Fourier-transform infrared spectroscopy revealed structural shifts (P < 0.05) in PSBM compared to SBM, including increased β-sheets, emergence of 3_10-helix, and reduced random coils and intramolecular aggregates. Compared to CSBM, PSBM had a higher proportion of fast-digestible protein (P < 0.001), representing a 21 % increase, and lower proportions of both slow-digestible (P = 0.001) and resistant protein fractions (P = 0.002). Compared to CSBM, PSBM had greater AID of CP, Lys, Met, and Thr (P = 0.001). The SID of Lys, His, and Val and total AA were greater in PSBM (P < 0.05) than CSBM. The PSBM tended to have greater AME than CSBM (P = 0.079). In conclusion, PSBM had modified secondary protein structure resulting in enhanced in vitro protein digestion kinetics profile, and improved digestibility of nutrients in broiler chickens.