Evaluation of Nonuniform Application of Phytase (Simulated) on Growth Performance and Bone Quality in Broiler Chicks

Abstract

The postpellet application of phytase can be variable and can lead to high coefficients of variation (CV). Two trials were conducted to evaluate the effects of high CV of phytase application (simulated by feeding 2 to 4 times the recommended level of phytase fed every second, third, or fourth day), when added to a standard broiler diet deficient in nonphytate phosphorus (NPP) and fed to 0- to 21-d-old male broilers. A standard curve of graded levels of NPP was included in both trials to determine the NPP requirement. Weight gain, feed efficiency, tibia breaking strength, and percentage tibia ash were assessed in both trials. Trial 1 was designed to evaluate the effect of a high variation (103% CV; 23,000 phytase units (PTU)/kg fed every other day) of added phytase fed on alternate days compared with low variation of added phytase fed daily (0% CV; 11,500 PTU/kg fed daily) and to determine the optimal phytase inclusion level and the NPP requirement. Trial 2 was conducted to determine the maximum variation of phytase addition fed alternate days and reevaluate the NPP requirement. When tibia ash was used as the response criterion, the NPP requirement was determined to be 0.42% in both experiments, and the optimal phytase level was determined to be 14,630 PTU/kg feed. The results of these studies also suggest that feeding a high variation diet of added phytase (103% CV) was not detrimental to the parameters evaluated. Only when the CV exceeded 103% was bone quality negatively affected.