Growth performance, feed efficiency and digestibility were studied for Sarotherodon galilaeus (Tilapia galilae) reared with two different initial weights of 20 and 50 g in concrete ponds (8 m2 area for each). The fish were stocked at a rate of 10 fish /m2 for small size and 5 fish / m2 for large one. They were fed on nine artificial diets containing different rates of protein (20, 25 and 30%) and energy (2500, 3000 and 3500 kcal/kg diet). At the end of experimental period (180 days) it was noticed that, fish fed on diet containing 25 % protein with 3000 kcal energy showed highest values of final body weight (130 and 204g), total weight gain (110 and 154g) and specific growth rate (1.04 and 0.79%) for the two initial weights respectively. With respect to feed efficiency, the feed conversion ratio had its optimum value was (1.88) at diet composed of 30 % protein and 2500 kcal, while highest protein efficiency ratio (2.15) and protein productive value (44.00) was observed at lowest dietary protein and highest energy for initial weight of 20 g . At initial weight of 50g, the best FCR (2.42) was obtained from fish fed diet containing 25 % protein with 3000kcal, but highest PER and PPV (1.73 and 39.20) were recorded at diets containing 20 % protein with 3500 kcal and 30 % protein with 3500 kcal respectively.Results of nutrients digestibility of two fish initial weights recorded the highest percent of dry matter digestibility (56.50 %) for fish fed on diet with 20 % protein and 3000 kcal. The maximum digestibility percent for crude protein and fats (85.00% and 88.50 %) were observed at diet containing 25 % protein with 2500 kcal. While the highest digestibility percent for carbohydrates (70.00 %) at diet containing 20 % protein with 3000 kcal and the highest energy digestibility (77.50 %) at 30 % dietary protein with 3500 kcal.
Key words: Growth performance, feed efficiency and digestibility, tilapia (Sarotherodon galilaeus).
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