A 3 x 3 factorial feeding trial was conducted to evaluate the effects of microbial phytase
(MP) supplementation fed with Ca/P ratio on growth, digestibility, vertebral mineralization and
some blood parameters in Nile tilapia Oreochromis niloticus. Three levels of phytase (0, 500 and
1000 U kg1 diet) were combined with three Ca/P ratios (0.3:1, 0.6:1 and 0.9:1), respectively.