Phytase supplementation in diets with low content of phosphorus and its effect on performance of broilers during the growth phase

The ingredients of vegetable sources contain phytate that causes low availability of phosphorus (P). This issue encouraged studies with enzymes such as phytase, which allows reducing the feed cost by increasing the bioavailable of complexed P in phytate. Thus, this study aimed to evaluate the performance of broilers fed diets with low content of phytic phosphorus and determine the optimal inclusion level of phytase in feed. For this trial, 1920 male broilers (Cobb 500) from 15 to 21-days of age were used. The birds were distributed in a completely randomized design with eight treatments, eight replicates and 30 birds per experimental unit. The treatments were: positive control (PC), with fully attendance of nutritional requirements; negative control 1 (NC1), with reductions of 0.15% in available P (aP) and 0.13% in calcium (Ca) and without phytase addition; and negative control 2 (NC2) with reductions of 0.17% in aP and 0.16% in Ca and without phytase addition. The other treatments were obtained from NC2, with increasing levels of phytase of 500, 750, 1000, 1500 and 2000 FTU/kg. At the end of the trial, the broilers and feed leftovers were weighed to estimate body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR). Data were analyzed by orthogonal contrasts, adopting 5% of significance and, to evaluate the optimal level of phytase, the broken line model was adjusted. The results showed that the Ca and P reductions negatively affected the performance. Phytase supplementation in NC2 provided higher BWG and FI values in comparison to PC (P<=0.01). There was significant (p<=0.01) responses between NC2 and the treatments with phytase supplementation. The data was used to adjust the broken line model resulting in the following equations: BWG = 400.1 (? 3.45) - 0.1502 (? 0.02)*(571.9 (? 57.76) - PHY), FI = 371.9 (? 5.24) - 0.1269 (? 0.03)*(586.4 (? 106.3) - PHY), and FCR = 1.1413 (? 0.02) - 0.0003 (? 0.0001)*(665.1 (? 213.5) - PHY). Thus, the optimal inclusion levels of phytase to maximize the response were: 572 FTU/kg for BWG, 586 FTU/kg for FI, and 665 FTU/kg for FCR. The results demonstrated that the phytase supplementation in diets with Ca and P reductions is able to improve the animal productive performance.