High levels of dietary phytase improves broiler performance

The objective of this study was to evaluate the effects of dietary phytase on broilers from 1 to 42 days of age. Five treatments were distributed in a completely randomized design, with eight replicates of 23 birds per experimental unit (per averages). The treatments consisted of a positive control diet (PC), a negative control diet (NC); and the NC diet + 1000, 2000 and 3000 FYT kg−1 phytase. The effects of dietary treatments on performance, bone quality and blood minerals were determined. From 1 to 21 days of age, WG, FI and FCR increased with increasing levels of phytase (P < 0.05), and from 1 to 42 days, body weight peaked with 2000 FTY kg−1 (P < 0.05). The best results for WG, FI and FCRC were obtained using 2051, 1992 and 2101 FTY kg−1, respectively. At 42 days of age, the Seedor Index (SI) and bone-dry matter (DM) were maximized at lower levels of phytase than for WG or FCR. The highest SI and DM values were obtained with 1553 and 1765 FTY kg−1, respectively. At 21 days of age, blood Ca content decreased with increasing phytase levels. Blood P exhibited quadratic behavior, with the maximum recorded at 1680 FYT kg−1 phytase. Tibia Ca increased with increasing phytase at 21 days of age (P < 0.05). Blood P at 42 days of age was lower than at 21 days, but did not vary between treatments. The apparent ileal digestibility coefficients of dry matter, mineral matter, crude protein and crude energy showed quadratic responses, with the highest coefficients obtained for the inclusion of 1164, 1592, 1085 and 1342 FYT kg−1 phytase, respectively. It is concluded that phytase improves broiler performance based on regression analyses. A high dose of 2973 FYT kg−1 had the best weight gain from 1 to 21 days of age. From 21 to 42 days, 2051 FYT kg−1 and 2101 FYT kg−1 showed the best weight gain and feed conversion ratio, respectively. These recommendations did not negatively affect the parameters evaluated.