Ascorbic acid biosynthesis by 3 species of Acipenceriformes and its role on quantitative growth parameters

Many vertebrates have L-gulonolactone oxidase (GLO) in liver or kidney, the enzyme catalyzing the last step in ascorbic acid biosynthesis; they can synthesize this vitamin as de novo, which is necessary for growth, health, bone formation, and reproduction. Due to this fact, 3 species of acipenserids were considered for effects of different levels of vitamin C. Results showed that in juvenile Siberian sturgeon, there were no significant differences in final weight after 16 weeks treated by 0 or 300 mg kg-1 ascorbic acid (P≥0.05). Also, there were no significant differences in growth and survival among groups of lake sturgeon after 38 days supplemented with 0, 50, 250, and 1250 mg kg-1 ascorbic acid (P≥0.05). Supplemented diets with 0, 100, 200, 400, 800, and 1600 mg kg-1 of ascorbic acid in great sturgeon also showed no significant differences in growth rate and final weight, however, survival showed enhancement in some treatments. Results obtained from this study showed that due to presence of GLO in this specimens, acipenserids do not require this vitamin in normal conditions, since rearing conditions such as high density, stressors, and pathogens, the need for this vitamin might increase in these fish, and it seems that, it is reasonable to use this vitamin in sturgeon diet in artificial rearing condition. In addition to tissue concentration, vitamin C can play a role as a peroxidant against free radicals.