The effect of phytase enzyme on apparent digestibility of four plant feedstuffs fed to rainbow trout (Oncorhynchus mykiss)

This study was conducted to determine the effect of phytase enzyme on phosphorus, protein, fat, dry matter and energy digestibility of four practical plant feed stuffs wheat meal (WM), corn meal (CM), wheat bran (WB), rice bran (RB) in rainbow trout feeding. Five diets containing of one reference diet include of fish meal, soybean meal and meat flour, were prepared. Feed stuffs were mixing 75% of base diet with 25% of WM or CM and 85% of based diet with 15% of WB or RB with similar gross energy. Chromic oxide was added at 0.5% of the diet and used as an indigestible marker. A phytase solution was sprayed post pelleting on the all diets at minimum concentration of fat 1000 phytase units per Kg (FTU/Kg) dry diets. Experiment was done in two cubic metric tanks that were filled with 500 liters water. Maximum and minimum temperature, oxygen and pH were 15 and 18 degree C, 8 and 6.8 mg/l and 7.7 and 7.5 respectively. Results showed that phytase had not significantly effect on amount of bone phosphorus and protein digestibility (p>0.05), but the amount of these indexes were increased with phytase supplementation. Moreover phytase significantly improved digestibility of dry matter. Results also showed that kind of diets had different effects on the nutrition digestibility. diets had not significantly effects (p>0.05) on the amount of bone phosphorus and protein digestibility but totally diets containing of WM, CM, WB and RB had better nutrition digestibility respectively that can use them in Rainbow trout diet due to their availability