Ameliorative effects of dietary Chlorella vulgaris and β-glucan against diazinon-induced toxicity in Nile tilapia (Oreochromis niloticus)

Abstract

The present study was carried out to investigate the toxic effects of diazinon on growth performance, hepato-renal function, antioxidant system, innate immune response and comparing the protective role of dietary Chlorella vulgaris (CV) algae and β-glucan in intoxicated Nile tilapia (Oreochromis niloticus). One hundred and eighty healthy Nile tilapia (20 ± 6.1 g) were distributed equally into four groups; control group, DZN group (0.28 mg/L), DZN-CV group (5% CV) and DZN-β-glucan group (0.1% β-glucan) and treatments conducted for about 60 days. The results revealed that administration of DZN significantly increased serum liver enzymes, uric acid, creatinine, and malondialdehyde (MDA) in different tissues. Meanwhile, glutathione (GSH) and superoxide dismutase (SOD) in different tissues, as well as IgM, C-reactive protein (CRP), respiratory burst, lysozyme and bactericidal activities were significantly decreased in DZN group. In addition, expression of TNF-α gene was up-regulated and IL-10 was down-regulated in spleen of DZN intoxicated fish. The treatment of DZN exposed fish with CV and β-glucan supplemented diets ameliorated hepatic damage and enhanced antioxidant activity and innate immune responses. Furthermore, dietary Chlorella vulgaris and β-glucan have a potent anti-inflammatory effect as they remarkably increased the expression of IL-10 and decreased TNF-α gene expression. The results also revealed that fish in DZN-CV group had the highest survival rate, final body weight (FBW) and body weight gain (BWG). On the other hand, feed conversion ratio (FCR), specific growth rate (SGR), and protein efficiency ratio (PER) of control, DZN-CV, and DZN- β-glucan were higher than DZN group. However, the hepatosomatic index (HSI) and spleen-somatic index (SSI) were higher in DZN group than other experimental groups. Overall, CV and β-glucan can be recommended as a feed supplement to improve immunosuppression, oxidative damage, growth performance and hemato-biochemical alterations induced by DZN toxicity in Nile tilapia.

Keywords: Antioxidant system; Fish health; Gene expression; Growth performance; Immune response; Immunostimulants; Pesticides.