Origanum sp. is a very common genus of aromatic plants worldwide distributed around the Mediterranean area and O. vulgare (oregano) is the most important species of this genus throughout the world. Due the known medicinal properties of oregano, the effect of diets enriched with 0% (control), 0.5% and 1% oregano leaves powder was studied on the growth, immune and antioxidant status of gilthead seabream (Sparus aurata L.). Fish fed with oregano 0.5% and 1% enriched diets improved both humoral (IgM and bactericidal activity in skin mucus and protease activity in serum) and cellular (head kidney leucocytes phagocytic ability) immunity at 15 and 30 days. Furthermore, the addition of oregano did not provoke any significant effect neither in the growth promotion nor in the liver antioxidant enzymes activity studied in the serum and skin mucus. The possibility of using O. vulgare as a functional additive to fish diet is discussed.

Department of Chemical Biological Pharmaceutical and Environmental Sciences University of Messina 98166 S Agata Messina Italy

Faculty of Fisheries and Protection of Waters South Bohemian Research Centre of Aquaculture and Biodiversity of Hydrocenoses Research Institute of Fish Culture and Hydrobiology University of South Bohemia in Ceske Budejovice Vodnany Czech Republic

Fish Innate Immune System Group Department of Cell Biology and Histology Faculty of Biology Campus Regional de Excelencia Internacional Campus Mare Nostrum University of Murcia 30100 Murcia Spain

Nutrition Group Institute of Aquaculture Faculty of Natural Sciences University of Stirling FK9 4LA Scotland United Kingdom

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