Effect of vitamin C on immune and stress responses in striped catfish, Pangasianodon hypophthalmus juveniles under pre- and post-challenge with Aeromonas hydrophila

A 60-day feeding experiment was conducted to evaluate the dietary effect of vitamin C on non-specific immunity and stress responses in striped catfish, Pangasianodon hypophthalmus juveniles with the average body weight of 3.23 +/- 0.01 g to 3.38 +/- 0.01 g. Seven graded levels of diets supplemented with 0, 17.5, 35, 70, 175, 350 and 700 mg vitamin C/kg diet as L-ascorbyl-2-polyphosphate were fed to fish in triplicates group. At the end of the experiment, fish fed vitamin C diet had significantly higher responses for nitroblue tetrazolium (NBT), serum lysozyme, phagocytic activities and lowest activities for superoxide dismutase (SOD) and catalase (p<0.05) under both pre- and post-challenge conditions with Aeromonas hydrophila. After a challenge, the percentage survival of fish fed vitamin C diet was improved than those of fish fed vitamin C-deficient diet. The overall results of the present study indicated that dietary vitamin C had a significant influence on immunity and stress mitigation in P. hypophthalmus juveniles. However, the highest positive response values obtained for immune and stress parameters in fish lies within the range of 350 to 700 mg ascorbic acid (AA) kg(-1) of the diet. From the present experiment, it may be concluded that the dietary vitamin C supplementation at the level of 350 to 700 mg AA kg(-1) of the diet would be optimal for influencing the immunity and stress responses in P. hypophthalmus juveniles.