Effects of Phytase Superdosing on Digestibility and Bone Integrity of Broilers

The effects of phytase superdosing on digestibility and bone development of broilers from 1 to 21 d of age were evaluated. Ninety-six male broilers of the Cobb Slow lineage were housed in metaboilic cages, distributed in a completely randomized design with 4 treatments and 8 replicates. The treatments were positive control without phytase, negative control with phytase (500 FTU), negative control with phytase (1000 FTU), and negative control with phytase (2000 FTU). From 16 to 21 d of age, total excreta samples were collected for digestibility analyses. To evaluate bone quality at 21 d of age, 2 broilers per experimental unit were slaughtered and the femur and tibia were collected. Data were analyzed by regression test. A quadratic effect of phytase inclusion for the diameter and percentage of Ca and P of the femur was observed, in which the inclusion of 1,494 and 1,220 FTU, respectively, showed the best results. For the evaluation of the tibia, the diameter, length and weight linearly increased with the inclusion of phytase, and for resistance a quadratic effect was observed, in which 1265 FTU was the best inclusion. Regarding digestibility, a quadratic effect for EEDC (Ether extract digestibility coefficient), MMDC (mineral matter digestibility coefficient), AME (Apparent metabolizable energy), and AMEn (Nitrogen-corrected apparent metabolizable energy) was observed, in which the inclusion of 1,734; 788; 1,204; and 1,255 FTU resulted in the highest values, respectively. Phytase superdosing improved bone development and broiler digestibility at 21 d.