Effect of a serine protease on the energy content of soybean meals of different origins in 22-d-old broilers

A total of 1,152 one-day-old straight-run Ross 308 broilers were used to study the effect of using a mono component serine protease (PRO; Ronozyme ProAct, DSM Nutritional Products) on the AMEn of soybean meals (SBM) from USA, Brazil (BRA), and Argentina (ARG). The design was a 3 × 2 factorial arrangement of 3 SBM of different origin (USA, BRA, and ARG) and 2 levels of PRO (0 and 200 mg/kg to give 0 to 15,000 PROT units/kg feed) resulting in 6 treatments. Each of the 6 treatments was replicated 24 times and the experimental unit was a cage with 8 broilers. Birds were fed a commercial corn-soybean meal diet from 1 to 18 d of age followed by the experimental diets that resulted from the combination of 42.6% SBM and 57.4% of a nitrogen free diet to 22 d of age. The AMEn of the diet was 1.4% and 3.8% higher in chicks fed USA SBM than in chicks fed BRA or ARG SBM (2,921 vs. 2,880 vs. 2,814 kcal/kg, respectively; P < 0.001). PRO supplementation increased the AMEn of the diet by an average of 1.1% (2,888 vs. 2,856 kcal/kg; P < 0.001). An interaction between SBM origin and protease supplementation was detected (P < 0.01); addition of PRO increased AMEn diet with USA or ARG SBM but not those with BRA SBM. In conclusion, AMEn of the diet based on USA SBM was higher than that of diets with BRA SBM, and was lowest for diets with ARG SBM ARG meals. PRO supplementation increased the AMEn of diets, an improvement that varied depending on the origin of the SBM