Submitted to: Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/21/1999
Publication Date: 1/30/2000
Citation: LIM, C.E., KLESIUS, P.H., LI, M.H., ROBINSON, E.H. INTERACTION BETWEEN DIETARY LEVELS OF IRON AND VITAMIN C ON GROWTH, HEMATOLOGY, IMMUNE RESPONSE AND RESISTANCE OF CHANNEL CATFISH (ICTALURUS PUNCTATUS) TO EDWARDSIELLA ICTALURI CHALLENGE. AQUACULTURE.185: 313-327, 2000. Interpretive Summary: Both iron and vitamin C are dietary essential for fish. The requirements of these compound for optimum growth and prevention of deficiency signs have been determined. Earlier research has also shown that iron and vitamin C are also important in the diets of fish in terms of their effect on immune system functions and host defense against infections. However, no studies have been conducted on the combined effect of dietary levels of iron and vitamin C on the response of fish. Thus, this study was conducted to evaluate the interactions between dietary levels of iron and vitamin C on growth, hematology, immune response and resistance of channel catfish to Edwardsiella ictaluri challenge. Results show that iron deficiency resulted in microcytic anemia as has been previously reported. Adding vitamin C in the absence of dietary iron accelerate iron deficiency as can be seen by rapid reduction in weight gain, survival and blood parameter values. Liver iron content was directly related to dietary level of iron. At high level of dietary iron (300 mg/kg), adding high level of vitamin C (3,000 mg/kg) further increased iron storage in the liver. Vitamin C at 3,000 mg/kg was needed to increase the number of a white blood cell (macrophage) migration. However, neither dietary iron nor vitamin C protect juvenile channel catfish from E. ictaluri infection although iron deficiency accelerate the onset of mortality. Thus, in the absence of clear cut information because nutrient deficiency predisposes fish to infection, adequate levels of iron and vitamin C to meet the requirements for growth and prevent deficiency signs are recommended.
Technical Abstract: Nine purified diets supplemented with three levels of vitamin C (0, 50 and 3,000 mg/kg) for each of the three levels of iron (0, 30 and 300 mg/kg) were each fed to juvenile channel catfish in triplicate aquaria twice daily to apparent satiation for 14 weeks. Fish fed iron-deficient diets had decreased weight gain, feed conversion and survival. Supplementation of ascorbic acid to the iron-deficient diets further decreased weight gain and survival. Feed conversion was not affected by dietary level of vitamin C or iron and vitamin C interaction. No gross signs of vitamin C deficiency were observed. Total cell count (TCC), red blood cell count (RBC), hematocrit (HCT) and hemoglobin (Hb) were significantly lower for fish fed the iron-deficient diet. TCC and RBC significantly increased when 3,000 mg of vitamin C/kg was added. However, in the absence of dietary iron, supplementation of ascorbic acid resulted in significant decrease in HCT and Hb. Liver iron content increased with increasing dietary levels of iron. Supplementation of high levels of ascorbic acid to the diet containing 300 mg iron/kg significantly increased the liver iron content. Liver ascorbate increased with increasing dietary level of ascorbic acid. Dietary level of iron and the interaction between iron and vitamin C had no effect on liver content of vitamin C. Mean macrophage migration was significantly higher for fish fed the iron supplemented diets. The significant effect of vitamin C was obtained only when 3,000 mg/kg was used. Neither dietary levels of iron nor vitamin C and their interaction influenced survival of fish against E. ictaluri 14-day post challenge. However, the onset of mortality was earlier for fish fed the iron-deficient diet.