A Review on the Effect of Ascorbic Acid on the Immune Response in Salmon

Due to the lack of L-gulonolactone oxidase enzyme, most fish species are unable to synthesize vitamin C (ascorbic acid) in sufficient quantity to meet metabolic needs, and thus have a requirement for this vitamin. Deficiency symptoms reported arestructural deformities, impaired collagen synthesis, decreased alkaline phosphatase activity, anemia, low tissue level of ascorbic acid, anorexia, growth retardation; poor feed efficiency, and delayed wound healing. The requirement of vitamin C by fish toprevent these deficiency signs rangs from 11 to about 100 mg/Kg of diet. Vitamin C has also been shown to influence immunity and disease resistance in fish. The immune system consists of innate (natural) and acquired (specific) immune mechanisms as have beenreported for terrestrial animals. Published information appears to indicate that a deficiency in ascorbic acid in immuno suppressive, and animals fed ascorbic acid-deficient diets are more susceptible to infectious disease than those fed vitamin C replete diets. However,evidence on the role of ascorbic acid in improving the immune response and disease resistance in fish is not consistent, although numerous studies have indicated that feeding fish ascorbic acid at levels higher than those required for normal growth and preventionof deficiency signs enhanced their immune response and resistanceagainst bacterial infection. Without clear evidence on the beneficial effect of high levels of ascorbic acid on the immune response and disease resistance, feeding fish vitamin C at a level sufficient tomeet their requirement for growth and prevention of deficiency signs is suggested.