Growth and physiological responses of broiler chickens to diets containing raw, full-fat soybean and supplemented with a high-impact microbial protease

Objective: This study evaluated the change and function of the pancreas, and small intestine in relation to growth performance of broilers on diets supplemented with raw soybean meal (RSBM) and protease. Samples of test ingredients and diets, after mixing and prior to being used were also assessed on contents of anti-nutritional factors. Methods: A $3{\times}3$ factorial study was used, with three levels of RSBM (commercial soybean meal [SBM] was replaced by RSBM at 0, 10%, or 20%) and protease (0.1, 0.2, or 0.3 g/kg). Each treatment was replicated six times with nine birds per replicate. Birds were housed in cages, in climate-controlled room and fed starter, grower and finisher diets. Results: Levels of trypsin inhibitors in the diets, containing varying levels of RSBM ranged between 1,730.5 and 9,913.2 trypsin inhibitor units/g DM. Neither RSBM nor protease supplementation in diets significantly affected (p>0.05) the body weight of broilers in the entire periods (0 to 35-d). Increasing the level of RSBM in diets increased the weight of the pancreas at d 10 (p<0.000), d 24 (p<0.001), and d 35 (p<0.05). Increasing levels of RSBM in the diets reduced the apparent ileal digestibility of crude protein (CP), and amino acid (AA) at d 24. Increasing level of RSBM in the diets decreased (p<0.01) pancreatic protein content, but this was increased (p<0.05) when protease was added to the diets (0 to 10-d). Increasing the level of protease improved the pancreatic digestive enzymes, including trypsin (p<0.05), chymotrypsin (p<0.01), and general proteolytic enzymes (p<0.05). Conclusion: The commercial SBM could be replaced at up to 20% by RSBM for broilers. Although protease supplementation slightly improved the digestive enzymes, and the ileal digestibilities of CP and AA, the CP and AA were negatively affected by increasing RSBM.