PROTEIN AND ENERGY-REQUIREMENTS OF NILE TILAPIA, OREOCHROMIS-NILOTICUS, FRY

The dietary protein and energy requirements of Nile tilapia, Oreochromis niloticus, fry were determined. Fifteen practical diets containing five protein (30, 35, 40, 45 and 50%) and three energy (300, 400 and 500 kcal GE/100 g) levels were prepared. The diets were fed to swim-up fry (12 mg) to satiation, three times a day, for 4 weeks. At all protein levels, groups of fry fed low-energy diets (300 kcal/100 g) exhibited extremely poor growth and feed conversion efficiency concomitant with high mortality rates, compared to those fed moderate- (400 kcal/100 g) and high-energy (500 kcal/100 g) diets. At dietary protein levels from 30 to 40%, fish growth and survival rates were significantly improved by increasing dietary energy from 300 to 500 kcal GE/100 g. At 45% protein, the best growth and feed utilization were achieved at 400 kcal/100 g diet with a protein-to-energy (P/E) ratio of 110 mg protein/kcal GE. At 50% protein, no further improvement in fish growth and feed conversion was evident at any energy level. Body composition was significantly affected by both dietary protein and energy levels. At each protein level, body protein and lipid content were positively correlated, while water and ash content were negatively correlated with dietary energy. The present study demonstrated that O. niloticus fry require 45% protein and 400 kcal/100 g for maximum growth when reared under laboratory conditions.