Abstract A trial was conducted to evaluate phosphorus release capacity in different commercial phytases throught performance and bone characteristics of broilers. A total of 2,400-day-old male Cobb 500® chicks were assigned in a completely randomized design with 12 dietary treatments ((1 to 5: with increasing levels of non-phytate phosphorus (NPP) (0.20; 0.25; 0.30; 0.35 and 0.40%) without phytase); and 6 to 12: with 0.20% supplemented with different commercial phytases), 8 replicates and 25 birds per pen. There was a linear increase (P<0.05) in the feed intake and body weight gain and a linear improvement (P<0.05) in the feed conversion ratio of broilers fed increasing NPP. The tested phytases did not release similar amounts of phytic phosphorus. Based on body weight gain response, 500 FTU/kg of diet releases a minimum and maximum of 0.074 to 0.152%, 0.062 to 0.157 and 0.059 to 0.169% of PP among the studied phytases in the periods from 1 to 21, 1 to 35 and 1 to 42 days, respectively. In conclusion, the commercial phytases released different concentrations of phytate phosphorus from the diets. Thus, is necessary to have a better method to evaluate phytase activity in order to avoid subnormal levels of available P in diets.

Abstract The trial was conducted to evaluate the supplementation of E. coli phytase on performance, weight and ash of bones, as well as to determine the bioavailability of P and cost/benefit of its use in diets. A total 1,890 Cobb male day old chicks were assigned to six treatments and seven replicates with 45 birds each, distributed in a completely randomized design. The treatments were: Positive Control; Negative Control (NC1) - reduction of 0.06% avP; Negative Control 2 (NC2) - reduction of 0.12% avP; NC2 + Phytase (120 OTU); NC2 + Phytase (180 OTU); NC2 + Phytase (240 OTU), being 1 OTU equivalent to approximately 2 FTU. With different phytase inclusions, it was possible to verify a gradual increase on body weight gain, feed intake, feed conversion ratio, viability and even the bone characteristics of broilers fed diets containing reduction of P. The closest levels to the highest studied (240 OTU) showed the best results. The replacement of dicalcium phosphate by phytase supplementation is economically viable when the cost per OTU does not exceed US$ 1.4 × 10-5, US$1.2 × 10-5 and US$ 1.0 × 10-5 for the concentrations of 120, 180 and 240 OTU, respectively.