Inclusion effect of onion peel powder in the diet of African catfish, Clarias gariepinus: Growth, blood chemistry, hepatic antioxidant enzymes activities and SOD mRNA responses

Abstract

This study evaluated the dietary effect of onion peel powder (OPP) on growth, blood chemistry, hepatic antioxidant enzymes activities and SOD mRNA responses of Clarias gariepinus. One hundred and twenty fish were randomly distributed into twelve plastic tanks and fed experimental diets for 42 days. Four diets (control, OPP-2, OPP-4 and OPP-6) were formulated with graded levels of OPP (0, 20, 40 and 60 g/kg diet) respectively. At the end of the experiment, the fish fed OPP supplemented diet exhibited significantly increased weight gain, specific growth rate (SGR) and better feed conversion ratio (FCR) compared to the control group (p<0.05). The highest values of haemoglobin (Hb) and erythrocytes (RBCs) count were observed in fish fed control diet (p<0.05). The pack cell volume (PCV, %) of the control and OPP-6 groups differs significantly (p<0.05) from other groups. Experimental fish group fed the control diet had the lowest total leukocytes (WBCs) and was significantly different (p<0.05) from other treatment groups. Dietary OPP significantly decreased (p<0.05) cortisol level when compared to the control group. The cholesterol, triglycerides and glucose values of fish fed OPP-2 were significantly higher (p<0.05) than other experimental groups including control. The antioxidant enzymes (catalase and glutathione) increased significantly (p<0.05) in fish fed graded levels of OPP diets compared to those fed the control diet. Furthermore, the control group had significantly decreased expression of superoxide dismutase (SOD) gene (p<0.05). Therefore, this study confirmed the beneficial effects of onion peel supplemented diet on growth, nutrient utilization, haematology and biochemical parameters and antioxidant enzymes activities of C. gariepinus.