The experiment was conducted to determine the effect of adding an exogenous protease enzyme to corn, soybean meal-base broiler diets. 350 male Ross 308 broiler chicks were placed in floor pens, with 10 birds per pen. There were 7 treatments, with 5 replicates each, fed in starter (d 1 to 21) and grower (d 22 to 42) phases. The dietary treatments were a positive control, formulated with 3,050 and 3,150 kcal of ME/kg and 1.27 and 1.12 % digestible lysine in the starter and grower phase, respectively, and a negative control, formulated with 3% reduction in ME and 5% reduction in digestible lysine as compared with the positive control diets. A mono-component protease (75,000 protease / g) was added to the negative control diets at 0,100,200,300,400 and 500 ppm of feed. Broilers fed the positive control diet grew better and had a better feed-to-gain ratio (FE) than did those fed the negative control diets, regardless of enzyme supplementation on protease supplementation had no effect on BWG and FI. FE was improved (p<0.05) as protease was increased. The result of this study shown that protease supplementation had a beneficial effect on FE but no effect on other performance measures as well as no adverse effect on carcass compositions.

 Keywords: Protease enzyme, metabolizable energy, digestible lysine, broiler diets