Effect of varying levels of dietary vitamin C (ascorbic acid) on growth, survival and hematology of juvenile tilapia, Oreochromis karongae (Trewavas 1941) reared in aquaria

Vitamin C (ascorbic acid) requirement of juvenile Oreochromis karongae was studied by incorporating varying levels of ascorbyl-2-polyphosphate in a 40% crude protein diet to obtain 0, 20, 40, 60 and 80 mg ascorbic acid equivalent kg-1 diet. Juvenile fish of 3.7g ± 0.02g initial body weight were used for the study. After 84 days of the experiment, the fish fed AA- supplemented diets had significantly (P < 0.05) higher specific growth rate protein conversion efficiency and protein efficiency ratio; and significantly (P < 0.05) better feed conversion ratios than non supplemented fish. Fish fed non supplemented diet recorded a 33 % rate of mortality, where as those fed with a diet supplemented with 60 mg ascorbic acid kg-1 had mortality as low as 4.4 %. Hematological indices showed a significant increase (P < 0.05) with dietary AA level. Diet containing 60 mg kg-1 of AA showed the maximum growth performance, while the broken line model gave 51 mg ascorbic acid kg-1 diet as the optimal level required by juvenile O. karongae. Our data show that ascorbic acid is essential for O. karongae growth performance.