Effect of nonphytate phosphorus and phytase levels on broiler femur

This experiment was carried out to evaluate the effect of nonphytate phosphorus (NPP) and phytase levels on the weight, morphometry and weight/length index (WLI) of broiler femurs at 21 and 42 days of age. One thousand, two hundred chicks were allocated in a completely randomized design and 4 x 3 factorial arrangement (NPP x phytase levels), with four replicates. The NPP levels, at each phase were of 0.45, 0.37, 0.29 and 0.21% in the initial phase, 0.41, 0.33, 0.25 and 0.17% in the growth phase, and of 0.37, 0.29, 0.21 and 0.13% in the final phase. The phytase levels used were 0, 500 and 1000U/kg of diet. At 21 and 42 days of age, 48 birds were sacrificed for femur collection. At 21 days, there was no effect (P > 0.05) of NPP x phytase interaction on bone parameters, but the NPP reduction decreased (P < 0.05) the weight, length and WLI of the femurs, and the inclusion of 500U/kg of phytase improved (P < 0.05) the weight and WLI of the bones. At 42 days of age, NPP x phytase interaction was significant (P < 0.05) for the weight and length, and birds fed diets with no phytase had femurs that were lighter and shorter when the lowest NPP levels were evaluated. However, the inclusion of 500 or 1000U/kg of phytase produced weights and lengths similar to those produced by treatment with recommended NPP levels, and the lower NPP levels evaluated caused a reduction (P < 0.05) in the diameter and WLI of femurs. It was concluded that diets with 0.29, 0.25 or 0.21% of NPP, with 500 U/kg of phytase, could be used with no negative effect on the femur quality in broilers from one to 42 days of age.