Soybean meal (SBM) is an ingredient with a high digestibility of protein, Lys, and Met. An optimal heating process of SBM is required to eliminate antinutritional components that negatively interfere with digestion, absorption, and metabolism of nutrients. The effect of 3 commercial SBM batches were subjected to different heat treatments to evaluate its effect on growth performance and intestinal integrity. A total of 1,860 male Cobb 500 broiler chicks were vaccinated at 1d of age with a commercial coccidia vaccine (Coccivac®-B52) via coarse spray. The 3 SBM batches were processed with different extruder temperatures of 182, 199, and 154 °C for normal-control, overcooked, and undercooked SBM, respectively. Increasing processing temperature ensured reduction of trypsin inhibitor, protein dispersibility index, and KOH solubility. Each treatment was fed to 10 pens of 62 birds from 0 to 35d of age. SBM was fed as a fixed inclusion in the diet, which notably SBM varied by CP by 49.2, 47.9, and 46.1 % amongst the control, overcooked, and undercooked SBM, respectively. Body weight gain (BWG), feed intake (FI), and feed-to-gain ratio (FCR) were recorded on d 0, 14, 28, and 35. The relative weights of the right pectoralis major (RPM) were determined from 5 birds per pen at 35d of age. The jejunal and ileal region of the small intestine was evaluated to calculate the villus to crypt length ratio on d14. Serum FITC-D concentrations was assessed in 1 bird per pen for gut permeability at d 16. Intestinal permeability increased in birds fed the overcooked SBM (P < 0.05). On d 14, 28, and 35, overcooked SBM depressed BWG, FI, and increased FCR (P < 0.05). The undercooked SBM decreased the villus height to crypt depth ratio in the jejunum on d14 and reduced BWG from 0-14 and 0-35d periods compared to the SBM control group. The relative weights of the RPM decreased significantly in 35 d-old birds fed overcooked SBM (P < 0.05). The adverse effects of overcooked SBM on BWG were driven by digestible amino acid (A.A) intake, which was lower (P< 0.05) for Lys, Met+Cys, and Thr in the overcooked treatment compared to the normal and the undercooked treatment groups. In conclusion, improper heat treatment of SBM affects bird performance and the intestinal integrity of broiler chickens. Key Words: Soybean meal, Heat treatment, Trypsin inhibitor, Protein dispersibility index, KOH solubility.
Key Words: Soybean meal, Heat treatment, Trypsin inhibitor, Protein dispersibility index, KOH solubility