Effects of phytase on enhancement of phosphorus utilization for feeds with plant materials in sex-reversed red tilapia (Oreochromis niloticus Linn.)

Sex-reversed red tilapia of initial weight 4.85-4.90 g were experimented for 10-wk in 235-l glass tanks filled with 180 l water. This experiment was conducted in closed-recirculating water system with 0.8 l/min flow rate. The 5x2 factorial experiment was employed in the study in which there were a total of ten treatments with three replications each. Twenty fingerlings were stocked in each replication. Two factors were studied the first of which was the animal:plant protein ratios 1:1, 1:2, 1:3, 1:4 and 1:5 were tested. For the second factor, the efficiency of phytase was studied for each animal to plant protein ratio by supplementing of 1,000 unit phytase/kg feed. The results showed that 1:3 animal to plant protein ratio was the most effective for sex-reversed red tilapia. Supplementation of 1,000 unit phytase/kg feed for all animal to plant ratios resulted in improvement of growth performance (weight gain and specific growth rate) feed efficiency (FCR, PER and ANPU), rate of feed intake and digestibility coefficient.