The Effect of Dietary Phytase Supplementation and Incubation in Soy Protein Concentrate based diet Fed to Nile Tilapia

Aquatic feed require high quality, low cost nutrients with increasing aquaculture production. Tilapia has become the third most important cultured fish species in the world, just after salmonids and carps. Soybean and its products are the most popular source of plant protein in compound aquatic feeds. In the existing plant protein sources phytate-P absorption and digestion is low in Nile Tilapia. This experiment aimed to investigate the different effects on retention and utilization of minerals and growth performance between phytase supplemented feeds in the SPC-base diets and without phytase SPC-base diet for three different size groups of Nile tilapia. Three diets for Nile tilapia were prepared with 100% plant protein concentrate. Diet 1 was made without phytase as control group. In Diet 2, 500mg phytase was added per kilogram of soy protein concentrate in the feed. Incubated Phytase was added in Diet 3. Each diet contained 100 mg Y2O3 kg-1 for determining apparent digestibility. In this experiment three different sizes of Nile tilapia with different numbers and same biomass in each tank were reared. Diet 3, with incubated phytase had not shown significant difference in growth performance, weight gain, feed intake and minerals retention except Zinc. Pretreated phytase decreased the mineral concentration in the fish body, plasma and feces. Pretreated Phytase increased the utilization and retention of minerals in Nile Tilapia during digestion and enhanced the apparent digestibility of minerals. The optimum dose of phytase in Nile tilapia feed is not determined. There are many factors which can affect the availability of phytase in Nile tilapia in the feed processing and production.M-F