Abstract This study was designed to investigate the effect of Neem seed oil on the oxidative stress in gills and erythrocytes (EC), after 1, 2 and 3 weeks (W) and to evaluate the antioxidant effect of lupine seed supplementation (LS) in the Nile tilapia Oreochromis niloticus. Two doses of Neem oil; 1/20 LC50:56 (NO1) and 1/10 LC50:112 PPM (NO2) and three periods of one, two and three weeks were used. Oxidative stress parameter, total peroxide (TP) and antioxidant enzyme activities, catalase (CAT) and superoxide dismutase (SOD) as well as glycemia were measured. NO2 markedly decreased CAT and SOD activities in gills at most periods (52 - 99% and 16 – 52 %, respectively) and in EC (22 - 62 and 48 – 63 %, respectively) in most periods, but NO1 had less effect. In turn, both doses significantly enhanced TP levels in gills and EC. Moreover, hyperglycemia was detected three weeks after control (NO) exposure. LS significantly curtailed or abolished the adverse effect of NO exposure on oxidative and antioxidant parameters in gills and EC. This may be attributed to the hypoglycemic effect of LS as well as its antioxidant efficiency. In conclusion, NO exerts oxidative damage in the fish and LS has an antioxidant potency.

Abstract This work aimed to study the toxicity of seed neem oil (NO) on oxidative stress in liver, white muscle and blood serum in the fish Oreochromis niloticus and the antioxidant effect of lupine supplementation (LS) against it. Healthy sixty six fish were selected. Two doses of neem oil; 1/20 LC50: 56.3 (NO1) and 1/10 LC50:112.5 PPM (NO2) and three periods of one, two and three weeks were used. The results showed that NO induced marked hyperglycemia and significant elevations in oxidative biomarker total peroxide as well as significant inhibition of antioxidants like catalase and superoxide dismutase activities in most experimental periods in the liver, white muscle and serum. In turn, administration of LS could abolish or at least, improve the adverse effect induced by NO exposure. This study suggests that sublethal doses of NO on fish led to generate oxidative damage in liver and white muscle. In addition, the antioxidant role of lupine seeds may be mainly due to its antihyperglycemic effect, as well as its contents of some natural antioxidants.