Evaluation of Phytase, Xylanase, and Protease in Reduced Nutrient Diets Fed to Broilers

Two experiments were conducted to evaluate phytase, phytase + xylanase, or phytase + xylanase + protease in diets deficient in Ca, available phosphorus (avP), energy, and amino acids. Lohman Indian River, straight-run broilers (n = 2,304 and 4,752 in experiments 1 and 2, respectively) were fed one of eight diets: (1) nutrient adequate control (PC), (2) negative control (NC) 1 with reduced Ca and avP, (3) NC1 + 1,500 FTU/kg phytase, (4) NC2 with reduced Ca, avP and energy, (5) NC2 + 1,500 FTU/kg phytase + 16,000 BXU/kg xylanase, (6) NC3 with reduced Ca, avP, energy, and amino acids, (7) NC3 + 1,500 FTU/kg phytase + 16,000 BXU/kg xylanase, (8) NC3 + 1,500 FTU/kg phytase + 16,000 BXU/kg xylanase + 15,000 U/kg protease. Reducing Ca, avP, energy, and amino acids significantly reduced body weight gain (BWG) and feed efficiency in a sequential fashion, with birds fed NC3 having a significantly higher FCR compared with birds fed NC1 or the PC. In both experiments, supplementation with phytase, phytase + xylanase, or the combination of phytase + xylanase + protease significantly improved BWG and FCR comparable to the PC. However, there was no difference in BWG or FCR between birds fed phytase + xylanase or phytase + xylanase + protease. Results indicate that supplementation of phytase + xylanase restored the BWG and FCR of the birds fed reduced Ca, avP, energy, and amino acid diets, and supplementation of protease to diets containing phytase and xylanase needs further investigation.