Nutrient utilization of Nile tilapia Oreochromis niloticus fed plant based low phosphorus diets supplemented with graded levels of different sources of microbial phytase

Experimental results regarding nutrient and phosphorus (P) utilization due to different sources of microbial phytase in tilapia nutrition are very scarce. An experiment was conducted with plant based diets (24.5% soybean meal; 11.5% wheat gluten; 22.5% corn; 32.5% wheat) containing moderate native phytase activity (< 300 FTU/kg). For comparison, a negative control diet (0.41% total P; 0.15% non-phytate P; no phytase added) and a positive control diet (0.88% total P; 0.62% non-phytate P; no phytase added) were used. Experimental diets with graded levels (500, 750, 1000, 1250 FTU/kg) of two different sources of microbial phytase (experimental phytase SP 1002; Ronozyme®P) were assigned in four repetition tanks and fed to juvenile all male Nile tilapia (average body weight 13.50 g) for 60 days. The efficiency of phytase supplementation was evaluated based on parameters of growth response, body composition, nutrient deposition and nutrient utilization following submission to ANOVA (P < 0.01) and Tukey-test. Significant improvements due to phytase addition (P < 0.01) were found for growth, feed conversion ratio, protein efficiency ratio, specific growth rate and nutrient deposition. Phytase supplementation increased energy-, protein- and phosphorus utilization significantly. In addition, the mineral composition of scale and vertebra was significantly affected. Ash content of scale and vertebra as well as P content in the ash of scale and vertebra were significantly increased due to improved P availability in the diet. Based on ingredients and composition of the diet under study, the experimental phytase SP1002 expressed superior performance data compared to Ronozyme®P. Supplementation of 750 FTU/kg from phytase SP1002 was similar to an inorganic P supplementation.