ARTICLE FEED & ADDITIVE MAGAZINE October 2022 73 known. Zinc is required for the metabolism of vitamin A. The strong redox potential of vitamin C may alter the valence of copper and iron and thus reduce or enhance absorption. Interactions between minerals usually have negative effects, but they can be beneficial (e.g. small copper supplements can enhance iron utilization) and may depend on the level of supplementation (e.g. large copper supplements can increase iron requirements). Mutual antagonisms between copper, cadmium and zinc lead to complex three-way interactions. Raising the level of one interactant can lower the status of the other two, as shown for Cd. MINERALS & FISH HEALTH Iron has been shown to affect immune system function and host defense against infection. Few studies have evaluated the effect of dietary iron on immune response and disease resistance in fish. Either a deficiency or an excess of iron can compromise the immune system (Beisel 1982; Bhaskaram 1988). Lall et al. (1985) observed that 4.5 mg of iodine/kg of diet was essential to protect Atlantic salmon from bacterial kidney disease infections. Selenium exerts the protective effects against the toxicity of heavy metals such as cadmium and mercury (Lall 1989). Supplementation of the diets with I, F, Fe, Cu, Co, Mn, and Zn resulted in a lower incidence of BKD infections. CONCLUSION Undoubtedly significant progress on the mineral requirements of aquatic animals has been made in the past two decades; overall developments in this field of fish nutrition have been relatively slow. Many gaps still exist in the knowledge of the quantitative requirements of inorganic elements and their physiological functions in most fish. In particular, limited information has been published on trace element metabolism of aquatic organisms. This creates great difficulties in the characterization of deficiency or toxicity symptoms even under controlled environmental conditions. Standard mineral mixtures used in warm-blooded animal experiments have not been effective in supporting optimum growth or preventing nutritional deficiencies in studies designed to investigate the nutrient requirements of finfish and crustaceans. Several pathological conditions and nutritional deficiency signs of unknown etiology have been observed in hatcheries, and aquaculture operations may in fact be due to a dietary mineral imbalance and either limited or excessive uptake of trace elements from the water. Wide differences exist among freshwater, euryhaline, and marine fish species in the absorption and utilization of certain dietary minerals. About Dr. Amit Ranjan Dr. Amit Ranjan is working as Assistant Professor in the Department of Fish Nutrition & Feed Technology at the Institute of Fisheries Post Graduate Studies of Tamil Nadu Dr. J. Jayalalithaa Fisheries University (TNJFU), India. He undertakes strategic and applied research in the field of fish and shrimp nutrition. He has good experience in commercial culture of shrimp and freshwater fish. He has published several research papers in international peer reviewed journals and serves as the reviewer of more than 30 international journals.
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