Dietary supplementation of polyphenols positively affects the innate immune response, oxidative status, and growth performance of common carp, Cyprinus carpio L.

The aim of the present study was to investigate the effects of polyphenols extracted from chestnut and olive mill wastewater on growth performance, skin mucus, and serum immune parameters as well as antioxidant defence in common carp (Cyprinus carpio L.) juveniles. For this purpose, common carp juveniles (15 +/- 0.3 g) were fed experimental diets containing different levels 0 (control), 0.05, 0.1, and 0.2% of polyphenols for 8 weeks. At the end of the trial, the growth parameters, haematological parameters, serum total protein, total immunoglobulin, lysozyme activity, and total antioxidant activity were measured in mucus and serum samples. The growth parameters revealed a significant increase in fish fed polyphenols containing diets compared to the control group (P < 0.05). In addition, the feed conversion ratio of fish fed polyphenols was significantly decreased (P < 0.05) compared to the control group. The serum and mucus total immunoglobulin (Ig) in fish fed polyphenols showed a significant increase compared to the control treatment with maximum values in fish fed 0.2% polyphenols extract. Also, the activity of lysozyme in skin mucus was significantly increased in fish fed 0.2% polyphenols (P < 0.05). At the end of the experiment, RBC and WBC count were significantly increased and mean cell volume (MCV) decreased in treated groups compared to the control group (P < 0.05). The serum antioxidant activity expressed by catalase and serum peroxidase activity was significantly increased in fish fed with diets supplemented with polyphenols with respect to the control group (P < 0.05). The results of the present study confirm the beneficial effects of dietary polyphenols on growth performance, immune parameters, and antioxidant defenc of common carp.