Dietary olive (Olea europaea) leaf extract suppresses oxidative stress and modulates intestinal expression of antioxidant- and tight junction-related genes in common carp (Cyprinus carpio)

Abstract The present study was conducted in order to evaluate the effects of various levels of dietary olive leaf extract (OLE) on growth performance, whole body lipid peroxidation, and intestinal expression of hsp70 and antioxidant- and tight junction-related genes in common carp. Common carp juveniles (15 g) were fed with four diets, i.e. control and three diets supplemented with 0.1% (0.1E), 0.5% (0.5E) and 1% (1E) OLE for eight weeks. The results revealed that there was no significant difference in growth performance and feed efficiency between the control and OLE-treated groups (p > 0.05). There was no change in oxidative conditions among the treatments after one week, but the control group showed oxidative stress after eight weeks. The 0.1E and 0.5E treatments showed significantly suppressed oxidative stress (p