LAUSR

Abstract The effect of dietary dehydrated lemon peel (Citrus limon) powder (DLPP) on growth, hemato-immunological, antioxidant and stress responses in rainbow trout (Oncorhynchus mykiss) was investigated. Fish (26.8 ± 1.9 g) were randomly introduced to four treatments feeding diets containing 0 (control), 0.5, 1.5, and 2.5% of DLPP diets. After a 45-day period, the fish were exposed to 10-day crowding stress. At the end of feeding trial, growth performance, hematological, immunological, antioxidant parameters and cortisol levels were assessed. The results showed that the dietary DLPP had no significant effects on the fish growth performance (p > 0.05). There were no significant differences in hematological parameters between the control and DLPP before the stress, but the white blood cell significantly (p   0.05). After stress, the immune activity, catalase and superoxide dismutase significantly increased in 1.5% DLPP (p > 0.05). The cortisol level significantly decreased in 0.5 and 1.5% DLPP compared to the control after stress (p > 0.05). Summary, dietary 1.5% DLPP supplementation has beneficial effects to reduce crowding stress and stimulates most of the antioxidant and immune characteristics of rainbow trout, without affecting the fish growth performance.