The present workwas designed to verify the effect of the use of phytase and xylanase upon theperformance and bone deposition of minerals in broiler diets containing 15%of rice bran, low available phosphorus and without supplementation of iron,zinc, copper and manganese. The phytase utilized was the Natuphos 5000 and thexylanase Avizyme 1300. The experimental design was the completely randomizedand the analysis of variance in a 4x2+1 factorial scheme. The control diet wasmade up of adequate levels of all nutrients without rice bran and without enzymes.The diets of the other treatments were formulated with 15% of rice bran withlow available phosphorus (40% of the recommended) and without inorganic supplementationof Fe, Cu, Zn and Mn with four levels of phytase (0, 400, 800 and 1,200 units/kg)with or without xylanase (1kg/t). The variables analyzed at 21 and 42 days ofage were performance and ash, P, Zn, Fe, Mn and Cu in the tibia. Live weightand feed intake increased significantly with supplementation of phytase whereasfeed conversion was not affected both at 21 and 42 days. The best level of phytaseof 1.105 and 1.023 FTU/kg for better performance was reached at 21 and 42 days,respectively. The xylanase did not affect significantly live weight and feedintake. Therefore the data shown a significant improvement in feed conversionat the two ages evaluated provided by lower feed intake by the birds fed dietssupplemented with xylanase. The phytase levels shown a linear increase in thecontents of ash and phosphorus in the tibia and did not affect the depositionof Zn, Fe, Mn and Cu in the two studied ages. The xylanase did not have anyeffect on the parameters evaluated in the tibia.
