Partial replacement of commercial soybean meal with raw, full-fat soybean meal supplemented with varying levels of protease in diets of broiler chickens

A 3 * 3 factorial study was used to evaluate the feed intake (FI), body weight gain (BWG), and feed conversion ratio (FCR) of broilers fed on the test diets. The commercial soybean meal (SBM) was replaced by raw, full-fat soybean meal (RSBM) at 0, 10 or 20%, equivalent to 0, 30 and 60 g/kg of diet, respectively, and the microbial protease was also supplemented in diets at 0.1, 0.2 or 0.3 g/kg, equivalent to ~7500, 15000 and ~22500 PROT/kg of diet, respectively. Microbial phytase (1000 FYT/kg) was uniformly added to each diet, which was fed to six replicate groups, with nine birds per replicate. Samples of test-ingredients and test-diets, after mixing, were also subjected to chemical analysis, prior to being used, to assess the nutritional compositions, particularly anti-nutritional factors. As the result of this study, the analysed concentrations of trypsin inhibitors (TI) in the diets ranging between 1730.5 and 9913.2 TIU/g. Increasing the levels of RSBM in the diets reduced the FI, during 1 to 35 d of age. Except in the starter phase, increasing the level of RSBM had no significant effect on BWG. When protease was added to the diets, the BWG was significantly improved during the periods of 1 - 10 d, 1 - 24 d and 1 - 35 d. Feed efficiency was decreased by increasing the level of RSBM (1-10 d). Neither increasing levels of RSBM nor protease affected the yield of any meat part at d 35. The relative weight of the small intestine at d 10 increased with rising levels of RSBM, but was reduced when protease was added to the diets. In conclusion, commercial SBM could be replaced by RSBM up to 20% in diets for broilers when the test microbial protease is supplemented.Keywords: Anti-nutritional factors, broiler chickens, carcass, growth performance, microbial protease, raw-full-fat soybean meal, trypsin inhibitors