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Two experiments were conducted to determine the effect of adding an exogenous protease to corn-, soybean meal-, and meat and bone meal-based broiler diets. In the first experiment, 1,764 male Ross 308 broiler chicks were placed in 63 floor pens, with 28 birds per pen. There were 7 treatments, with 9 replicates each, fed in the starter (d 1 to 21) and grower (d 22 to 40) phases. The dietary treatments were a positive control, formulated with 3,050 and 3,150 kcal of ME/kg and 22.5 and 20% CP in the starter and grower phases, respectively, and a negative control, formulated with a 4.4% reduction in ME and CP 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, 400, 800, and 1,600 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. Protease supplementation had no effect on BW; however, FE was improved in a quadratic manner as protease was increased. In experiment 2, a factorial arrangement of 2 protein (7% difference in CP), 2 energy (3% difference in ME), and 2 protease (0 and 200 ppm) concentrations was used, resulting in 8 treatments replicated 11 times (22 male Cobb 500 broilers per replicate). No 3-way interactions were observed for live performance measures. Broilers fed the high-protein and high-energy diets performed better (P ≤ 0.01) than those fed the low-protein and low-energy diets. Protease supplementation improved FE as well as digestibilities of fat and CP (P ≤ 0.01), regardless of dietary protein or energy concentration. The protease used in these studies improved FE and dietary determined AME values as well as dietary CP and fat digestibility values.
Freitas et al. (Thu,) studied this question.