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 ofvitamin 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 thecontrol 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