Effect of different levels of L-ascorbic acid (0, 250, 500, 750, 1000, 1250 and 1500 mg/kg dry diet) on growth and physiological properties of Tilapia galilae (Sarotherodon galilaeus) were studied. Fish of an initial size of 12 cm for total length and 40 gm for body weight were stocked in concrete ponds (40 m2 area) at a rate of 5 fish / m2. At the end of experimental period, it was noticed that the final total length and body weight reached its highest values (27.5 cm and 186.5g) in fish fed diet containing 750 mg vitamin/kg diet. While, the specific growth rate and normalized biomass index give showed its maximum values (1.08 and 0.72) in case of fish fed diets containing 750 mg vitamin / kg diet. Similarly, the feed conversion ratio had its optimum value (2.85) and protein efficiency ratio reached its highest value (1.49) at the two pervious vitamin levels. The better biological indices of rearing fish (hepato, gonado and gastrosomatic indices) were recorded for fish fed with diets containing 750 mg vitamin / kg diet. The survival rate and total fish production had its maximum values (98% and 3.839 tons/feddan) for fish fed on the diet containing 750 mg vitamin / kg diet. It was also noticed that, the fish health was improved when fed on diets containing 750 and 1000 mg vitamin c, where the blood parameters and biochemical composition of muscles reached its highest values.
Key words: Vitamin c, growth rate, biological indices Sarotherodon galilaeus, feed utilization, survival rate, blood parameters, muscle analysis.
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