Growth response and carcass composition of red tilapia fry fed diets with varying protein levels and protein to energy ratios

An 8-week feeding experiment was conducted with red tilapia (Oreochromis ) fry of 0.160 plus or minus 0.035 g initial weight. Twelve diets of 4 protein levels (25, 30, 35 and 40%) and 3 protein to energy (P/E) ratios (111, 100 and 80 mg protein/kcal) at each protein level were used. The highest growth was attained by fry fed a 40% protein diet with a P/E ratio of 111 mg/kcal. A lower but not a significantly different growth response was attained by fry on a 35% protein diet with a P/E ratio of 111 mg/kcal and a 30% protein diet with a P/E ratio of 100. Protein efficiency ratio was affected by the dietary protein level. Feed conversion ratio was not significantly influenced by the dietary protein level nor the P/E ratio. Carcass moisture content (%) was affected only by the P/E ratio. Carcass moisture content was directly related to the P/E ratio of the diets and was inversely related to the digestible energy (DE) level. Both protein level and P/E ratio significantly influenced carcass lipid content (%) on a dry matter basis but not the ash content. Carcass lipid (5) increased with increasing dietary protein and increasing DE levels of the diet, but decreased with increasing P/E ratio. Carcass protein content decreased significantly with the decrease of P/E ratio and increase of DE level of the diet