Potential amelioration of waterborne iron toxicity in channel catfish (Ictalurus punctatus) through dietary supplementation of vitamin C.

Iron overload in water is a problem in many areas of the world, which could exert toxic effects on fish. To achieve maximum growth and overall fitness, iron induced toxicity must be alleviated. Therefore, this research was undertaken to investigate the potential mitigation of iron toxicity by dietary vitamin C supplementation in channel catfish (Ictalurus punctatus). Two doses of vitamin C (143 and 573 mg/kg diet) were tested against high environmental iron (HEI, 9.5 mg/L representing 25% of 96 h LC). Fish were randomly divided into six groups with four replicated tanks. The groups were Control (vitamin C deficient feed), LVc (143 mg vitamin C supplemented per kg diet), HVc (573 mg vitamin C supplemented per kg diet), Con + Fe (control exposed to HEI), LVc + Fe (LVc exposed to HEI) and HVc + Fe (HVc exposed to HEI). Following an 8 week trial, there was a significant reduction in weight gain (WG%) in Con + Fe compared to the control, indicating a toxic effect of HEI on fish growth performance. Interestingly, WG% in both LVc + Fe and HVc + Fe groups were significantly higher than Cont + Fe, signifying that HEI inhibited growth, but this was alleviated by vitamin C. Both hemoglobin content and hematocrit were higher in LVc + Fe compared to the control and Con + Fe. In addition, exposure to HEI (Con + Fe) incited hepatic oxidative stress based on an over-accumulation of malondialdehyde (MDA) along with a significant inhibition in superoxide dismutase (SOD) and catalase (CAT) activities; whereas in LVc + Fe and HVc + Fe, the MDA content restored to basal level. A series of histopathological alterations were observed in the liver and gills, with the most severe lesions in Con + Fe, which was also complemented with a remarkable increase in hepatic iron accumulation. Vitamin C supplementations reduced the augmented concentrations of iron accumulation to that of the control. No effect, regardless of the treatments, was noted for fatty acid composition of muscle. Overall, our findings suggest that the vitamin C supplementation can be an effective therapeutic approach for boosting growth as well as alleviating iron toxicity in catfish.