Vitamin C (ascorbic acid) requirements of Heterobranchus longifilis fingerlings

A feeding experiment was conducted to quantify the minimum dietary vitamin C requirement of Heterobranchus longifilis fingerlings. Fish were fed a basal diet with 42.5% crude protein for a conditioning period of 2 weeks. Following conditioning, fingerlings with initial mean weight, 2.3 ± 0.3 g were stocked as groups of 20 fingerlings into 30 litre tanks in a mini-flow through experimental system. Graded levels (0, 50, 100, 150, 200 and 250) mg of L-ascorbic acid kg-1 diet was included into the basal diet by replacing part of the silica component and fed to triplicate groups for 20 weeks. Fish fed the control (0 mg vitamin C kg-1) diet exhibited deficiency signs including lordosis, caudal fin deformity, skin erosion and significantly (P < 0.05) suppressed weight gain and higher condition factor. Protein efficiency ratio and specific growth rate were significantly (P < 0.05) improved with increasing levels of vitamin C up to 200 mg kg-1 diets. Tissues (liver, kidney, gills and muscle) ascorbate concentration generally reflected dietary inclusion levels with significant (P < 0.05) lowest level occurring in the control groups. The dietary requirement based on least mean squares error regression analysis of weight gain and specific growth rate data on inclusion level of vitamin C was 82.2 ± 0.2 mg vitamin C kg- 1 diet which corresponds to 100 mg of vitamin C kg-1 diet.