The aim of this study was to evaluate the antioxidant potential of lemon pumace powder (peel and pulp), as an inexpensive and valuable source of nutrient in diet of common carp. Fish (60 ± 5 g) were divided randomly into four groups of 30 each. Group 1 fish were fed with basic diet, serving as the control. Fish in group 2 and 3 and 4 were fed the basic diet supplemented with 1.5%, 3% and 5% lemon pumace powder, respectively. Results showed that growth performance including final weight, weight gain (WG), feed conversion ratio (FCR) and specific growth rate (SGR) significantly increased as compared to control. Malondialdehyde (MDA) values of muscle significantly increased as compared to control in all treatment groups and the decreeing effect of lemon pumace powder on malondialdehyde (MDA) values of kidney and liver was only significant in group 4, when compared with the control group (p < 0.05). Protein carbonyl contents were significantly decreased in kidney and liver in group 3 and 4 as compared to control group and protein carbonyl of muscle significantly decreased as compared to control in all treatment groups. FRAP values of liver significantly increased only in group 3 as compared to control, and FRAP values of kidney and muscle significantly increased only in group 4 as compared to control (p < 0.05). These data suggest that supplementation of 5% lemon pumace powder to be more effective than its lower levels in strengthening the antioxidant system against oxidative stress.

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