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Efficacy of a mono-component protease is affected by trypsin inhibitor concentration in soybean meal

Wedekind, K., J. Chen, F. Yan, J. Escobar and M. Vazquez-Anon

Three experiments were conducted to quantify the efficacy of exogenous protease in poultry diets containing soybeans with varying trypsin inhibitor (TI) concentrations. Test diets contained 4 g/kg of TiO2 as a digestibility marker and protease (CIBENZA® DP100 at 300 U/g diet, Novus International). A randomized complete block design was analyzed using ANOVA with LSD multiple pair-wise comparison used to compare treatment means. For Exp 2 and 3, a common starter diet was fed to broiler chickens until d 16 of life and then switched to test diets. Exp 1 was a 2×6 factorial arrangement of 2 protease levels (0 and 300 U/g) and 6 dietary TI levels (0.72, 1.16, 1.61, 2.06, 2.50, and 2.95 mg/g) with 6 replicates/treatment; 8 chicks/pen. In Exp 2 (12 replicates/treatment; 8 chicks/pen), apparent ileal AA digestibility (AIAAD) was evaluated in diets containing 250 g/kg full fat extruded soybeans (FFES)+SBM (negative control; 5.8 mg/g TI) with or without protease or SBM (positive control; 3.1 mg/g TI). Test diets were fed from d 16–21 of age, AIAAD and relative pancreas weight was measured on d 21. In Exp. 3, broilers were allocated to a 2×2 factorial arrangement of treatments with 9 replicates/treatment and 8 chicks/pen. The dietary factors were SBM inclusion (420 or 960 g/kg; SBM TI = 3.85 mg/g), or protease inclusion (0 or 300 U/g). Test diets were fed from d 22–30, ileal digesta was collected on d 30. With increasing TI, pancreas weight increased (P<0.05; Exp 1 and 2), and AIAAD decreased (P<0.05; Exp 1–3). Protease decreased pancreas weight (P<0.05) and improved AIAAD in Exp 2 (P<0.05; average AIAAD increase was 3 %). In Exp 3, protease increased (P<0.05) AIAAD only in diets containing high TI (average AIAAD improvement was 3.6 %).

In conclusion, protease could be effective in mitigating high TI in SBM by increasing AIAAD digestibility.