POTENTIAL APPLICATION OF DIETARY SUPPLEMENTATION OF VITAMIN C IN ENHANCING GROWTH AND MITIGATING IRON TOXICITY IN CATFISH

Catfish is the leading and most successful aquaculture industry in the U.S., with channel catfish (Ictalurus punctatus) being the predominant species. The success of catfish aquaculture is highly dependent on the superior feed as well as the water quality of the production systems. In most parts of the U.S. the main source of water for fish culture is deep underground water which is high in iron content. However, when certain threshold levels of iron are exceeded in the water, it can exert toxic effects on fish. Nevertheless, for the profitable catfish aquaculture, it is important to find a solution that can have a dual benefit of -promoting growth as well as mitigating the toxic effect of waterborne iron.

Therefore, this work investigates the potential application of dietary supplementation of vitamin C in the diet of catfish. A total of 360 catfish juveniles (average weight: 42.72 ±0.42g) were distributed into 6 groups with three replicates (20 fish per tank). Fish fed three isonitrogenous (35% crude protein) and isolipidic (8% lipid) diets, and two different levels 143 ppm and 573 ppm of vit. C for 8 weeks. All groups were also exposed to elevated iron (9.5 mg/L Fe³⁺, representing 25% of the determined 96 h-LC₅₀ value). As such there were six groups viz (i) Control (Con; fed with commercial diet), (ii) diet supplemented with low vit. C (143 ppm; LVC), (iii) with high vit. C (573 ppm; HVC), (iv) Control exposed with elevated iron (Con+Fe), (v) LVC exposed with elevated iron (LVC+Fe), and (vi) HVC exposed with elevated iron (HVC+Fe). At the end of the feeding trial, production performance (weight gain %) of LVC+Fe group were significantly reduced compared to the control (Fig. 1), suggesting growth inhibiting effect of iron. Interestingly, fish fed with vit. C (LVC and HVC) had significantly higher weight gain (%) relative to control, signifying growth promoting effect of vit. C. Moreover, superior growth performance of LVC+Fe and HVC+Fe groups in comparison to Con+Fe (Fig. 1), indicate potentiality of vit. c in mitigating toxic effect of iron. Beside growth related parameters, blood chemistry (hemoglobin content, hematocrit), iron burden in the plasma and liver, oxidative status as well as histopathology examination of liver and gills were conducted to validate the potential benefit of dietary vit. C.  Conclusively, it can be stated that vit C supplementation can be an effective approach for boosting growth as well as alleviating iron toxicity in catfish.