Comparing the effect of diet supplementation with different zinc sources and levels on growth performance, immune response and antioxidant activity of tilapia, Oreochromis niloticus

The current study was designed as (2 × 3) factorial groups of 20 and 40 mg Zn/kg diet from each inorganic (zinc oxide), organic (Zn‐methionine) and nanoparticle (nano‐zinc oxide) sources supplemented to six Nile tilapia (O. niloticus) fingerling diets. The results showed both organic and nano‐Zn‐administered groups, especially at 40 mg/kg, exhibited significant improvements in body weight, total gain, feed conversion ratio and specific growth rate as compared to inorganic Zn‐supplemented groups. Nano‐Zn, at 20 and 40 mg/kg diet, increased haemoglobin, WBC counts, as well as lysozyme, IgM, and serum bactericidal test compared with other sources. Increasing Zn levels progressively increased serum and muscle Zn contents in nano‐Zn groups. Antioxidant capacity (TAC, SOD, and CAT) also increased in nano‐Zn‐supplemented fish at 40 mg/kg diet. Although the mRNA expression profile of growth hormone (GH) and insulin‐like growth factor 1 (IGF‐1) showed an up‐regulation in both organic and nano‐Zn‐supplemented fish, a dose‐dependent up‐regulation was observed for the expression of hepatic antioxidant (SOD and GPx) and immune (IL‐1β and TNF‐α) encoding genes in nano‐Zn‐administered groups alone. The highest resistance against Aeromonas hydrophila was observed in the nano‐Zn‐supplemented group at 40 mg/kg diet. Thus, it can be concluded that zinc nanoparticles are potential alternatives to conventional zinc sources in Nile tilapia.