Evaluation of novel protease enzymes on growth performance and nutrient digestibility of poultry: enzyme dose response.

Two experiments were conducted to evaluate 3 novel proteases in broilers. In experiment 1, 600 male, Cobb 500 broilers were allocated to 1 of 12 experimental diets (5 birds/pen and 10 replicates/diet). A control (C) diet was formulated to be adequate in all nutrients. Proteases 1, 2, or 3 were added to this diet at 3 doses (1x, 3x, or 9x) in a 3 × 3 factorial arrangement of treatments. The factorial was augmented with 2 treatments of phytase at 500 or 1,500 FTU/kg added to the C diet. In experiment 2, 2,050 male Ross 308 broilers were allocated to 1 of 10 experimental diets (25 birds/pen and 9 replicates/diet). A C diet was formulated to be adequate in all nutrients. Protease 1, 2, or 3 was then added to the C diet at 3 doses (1x, 2x, or 4x) in a 3 × 3 factorial arrangement of treatments plus the C. In experiment 1, birds fed phytase gained more (P < 0.05) than birds fed protease, but neither were different than birds fed the C. Supplementation of 9x dose of any protease resulted in a reduction (P < 0.05) in BWG when compared with birds fed 1x dose of protease or phytase at 500 or 1,500 FTU/kg. Feed conversion ratio was improved (P < 0.05) in birds fed phytase compared with birds fed the C diet. Nitrogen digestibility was greater (P < 0.05) in birds fed protease 1 when compared with birds fed protease 2. Birds fed the 1x dose of protease or 500 FTU/kg of phytase had a greater (P < 0.05) N digestibility than birds fed 3x dose of protease. In experiment 2, protease supplementation significantly reduced (P < 0.05) BWG when compared with birds fed the C from hatch to 35 D post-hatch. Protease supplementation did not improve broiler growth performance or N digestibility above that of a nutrient adequate control diet or a diet supplemented with 500 FTU/kg of phytase.