Impact of lactoferrin supplementation on oxidative stress, gene expression and immunity dysfunction induced by Aeromonas veronii in Nile tilapia ( Oreochromis niloticus )

This study investigated the effect of bovine lactoferrin (LF) dietary supplementation on haematological and immunological parameters, antioxidant genes, stress markers and disease resistance in Nile tilapia (Oreochromis niloticus) compared with that of oxytetracycline. Experimental fish were allocated into different groups as follows: Group 1, the control group, was fed a basal diet without any additives; Group 2 was fed a diet containing LF at a dose of 800 mg/kg; Group 3 was fed a diet containing LF at a dose of 1200 mg/kg; and Group 4 was fed a diet containing oxytetracycline (500 mg/kg diet) daily for 30 days to compare their effects before infection with Aeromonas veronii on the 15th day of the experiment and after infection on the 30th day of the experiment. Total white blood cell count, heterophils, IgG and total antioxidant capacity were not affected by dietary supplementation with either LF or oxytetracycline before infection. However, there was an interface between dietary LF supplementation with either 800 or 1200 mg/kg in improving haematological and immunological parameters and decreasing stress markers before and after infection. Expression profile of renal and splenic inflammatory (IL-10, IFN-γ, IL1b, TLR9, TNF-α, IL-21, IL-6 and Caspase3) markers was also upregulated compared with those in the control and oxytetracycline groups. The modulated expression profile of hepatic antioxidant (CAT, SOD, GPx, Nrf2i and Keap1) markers was significantly upregulated compared with those in the control and oxytetracycline groups. However, Keap1 seemed to be downregulated.