Nutrient digestibility of broiler chickens fed on a low-protein diet supplemented with mono-component proteases

The study was conducted to investigate the effects of microbial enzymes (serine proteases) on apparent ileal energy, crude protein and amino acids digestibility of broilers fed on low-protein diets. A total of 96 male broiler chicks were used in a 2x3 factorial design arrangement. Treatments were two levels of crude protein (CP16% and CP19%), and three levels of exogenous enzyme supplementation (0 mg/kg, 500 mg/kg enzyme A = EA, and 200 mg/kg enzyme B = EB) during the finisher stage. On day 27, ileal contents were collected from all birds for determination of apparent ileal digestible energy (AIDE), crude protein (CP) and amino acids (AA). The results showed that CP19 diets had significantly higher AIDE and CP and AA digestibility than CP16 diets. The digestibility coefficients of energy, CP and a majority of AA (His, Leu, Lys, Met, Phe, Thr, Val, Gly, Ala, Asp, Pro, Ser and Tyr) were improved (P<0.01) with supplementation of EA compared to those of EB or control. Enzyme supplementation had no effect (P>0.05) on the digestibility of Arg, Ileu, Cys and Glu. Except for Lys and Met, the digestibility of all other remaining essential and non-essential AA were influenced significantly by dietary protein level. Only the Arg and His digestibility were influenced (P<0.05) by diet x enzyme interactions. In conclusion, the beneficial effects of exogenous protease supplementation appeared to be dependent on the enzyme source and not dependent on the dietary level of protein.