Vitamin C supplementation to optimize growth, health and stress resistance in aquatic animals

Vitamins are organic compounds that can be synthesized from other essential nutrients; however, they are required in trace amounts from an exogenous source for normal growth, reproduction and health. Vitamin C (ascorbic acid, AA) is an essential micronutrient for normal growth and physiological function of most aquatic animals. In terrestrial animal nutrition, vitamin C has recently spurred scientific interest because of the increasing knowledge on vitamin C involvement in gene expression, cell cycle and reproduction in mammals; in addition, recent advances in molecular biology techniques allow the more effective estimation of the effect of vitamin C on metabolism and physiology. In contrast, this information is scarce in aquatic animal nutrition, as studies have essentially focused on the estimation of minimum vitamin C requirement for maximum growth and immune response as well as for the formulation of least-cost diet. This scarcity of information is also due to the lack of well-established indicators of vitamin C status in aquatic organisms. The present review summarizes and discusses information about vitamin C sources, bioavailability, deficiency and requirement in aquatic animals to plan further studies. In the future, vitamin C nutrition studies in aquaculture should also include immune responses, histopathology of the gills, liver, gonad development, gamete quality and quantity, fecundity, larvae survival and gene expression. Dietary vitamin C requirements should be estimated at every life-history stage of cultured species. All this information will allow a better understanding of the essentiality of vitamin C in aquatic animal growth, development, reproduction and health.