Influences of calcium/phosphorus ratio on supplemental microbial phytase efficiency for Nile tilapia (Oreochromis niloticus)

A 3 × 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 kg−1 diet) were combined with three Ca/P ratios (0.3:1, 0.6:1 and 0.9:1), respectively. The Ca/P ratios were achieved by supplementing calcium propionate at (0, 5 and 10 g kg−1 diet). After a 84-day feeding trial, tilapia fish fed 500 and 1000 U kg−1 diet at Ca/P ratio (0.6:1) had significantly higher growth rate, feed intake (FI) crud protein, vertebrae ash and phosphorus than other groups. Interaction between Ca/P and MP are significantly (p < 0.001) affected by all parameters of digestibility and blood parameters. The highest apparent digestibility recorded by fish fed diet supplemented with 1000 U kg−1 with 0.6:1 Ca/P ratio. The highest triglyceride was found in fish fed MP 500 or 1000 U kg−1 and combined with 0.6:1 Ca/P ratio, while, fish fed MP 500 U kg−1 with Ca/P 0.6:1 showed the highest value of cholesterol and serum. No significant differences were found in serum aspartate aminotransferase (AST) and alanine aminotransferase ALT of fish fed experimental diet.