Nano zinc oxide stimulates growth, increases immunity and disease resistance in catfish

Zinc (Zn) is an important trace element in fish diets, essential for growth, immunity and antioxidant defense mechanisms. The present study evaluated the effects of both organic zinc oxide and nano zinc oxide (ZnO and ZnO-NPs, respectively) on growth performance, immune response and antibacterial effects against Pseudomonas aerugino s a in African catfish Clarias gariepinus . Fish were fed either a control diet or a diet supplemented with organic ZnO at concentrations of 20 and 30 mg kg -1 or nanozinc oxide ZnO-NP at concentrations of 20 and 30 mg kg-1 . After 60 days, a subset of fish were injected intraperitoneally with 3 × 10 7 CFU ml -1 among P. aeruginosa . The results showed that body weight gain, feed conversion ratio and specific growth rate were significantly increased in ZnO-NPs20 compared with all other groups. Dietary supplementation with 20 mg kg -1 of ZnO-NP improved the antioxidant status of fish. Furthermore, IgM, lysozyme and nitric oxide showed significant increases in fish fed diets supplemented with ZnO-NPs20. The group supplemented with ZnO-NPs20 had significant upregulation of genes related to growth and stress compared with the other groups. However, there was no significant difference in the expression of immune-related genes between the ZnO-NPs20, ZnO-NPs30 and ZnO30 groups. These findings highlight the possibility of using ZnO nanoparticles to improve growth performance, antioxidant status, immune status and antibacterial activity against P. aeruginosa  in African catfish.

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