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¹ University of Jiroft, Department of Fisheries and Environmental Sciences, Faculty of Natural Resources, Jiroft, Kerman, Iran
² Shahrekord University, Department of Fisheries and Environmental Sciences, Faculty of Natural Resources and Earth Sciences, Shahrekord, Iran DOI : 10.4194/1303-2712-v20_3_05 Viewed : 5364 - Downloaded : 3861 The present study was carried out to evaluate the moderating properties of oregano (Origanum vulgare) (ORG) extract on the toxic effects of organophosphate pesticide, diazinon on growth and some metabolism associated components of rainbow trout, Oncorhynchus mykiss. In non-diazinon-exposed fish, the triiodothyronine (T3) levels in serum and body weight index (BWI %) and specific growth rate (SGR) values were higher in fish supplemented with 2, 6 and 10 g ORG/kg diet compared to control (nonORG-supplemented fish) and fish fed 14 g ORG/kg diet after 60 days feeding trial (P<0.05). Furthermore, the serum thyroxine (T4) levels increased in fish fed 6 and 10 g ORG/kg diet compared to control and those supplemented with 2 and 14 g ORG/kg diet (P<0.05). Fish supplemented with 14 g/kg ORG diet showed the lowest BWI %, SGR and serum thyroid hormones (P<0.05). The lowest FCR values were observed in fish supplemented with 6 and 10 g ORG/kg diet (P<0.05). In diazinon exposed fish, thyroid hormones, BWI % and SGR significantly declined during 60 days exposure to diazinon in control and ORG-supplemented fish (P<0.05). However, these parameters were found to be higher in fish supplemented with 6 and 10 g ORG/kg diet compared to other exposed fish (P<0.05). FCR values significantly increased in control and fish supplemented with 2, 6 and 14 g ORG/kg diet after exposure (P<0.05). The levels of cortisol significantly elevated during exposure to diazinon in control and fish supplemented with 2 and 14 g ORG/kg diet (P<0.05). The glucose levels significantly increased in fish fed 6 and 10 g ORG/kg diet (P<0.5). During exposure period, diazinon induced ranges of histological lesions in liver, which the severity of theses lesions was lower in ORG-supplemented fish (P<0.05). In conclusion, ORG at optimum dietary levels (6-10 g/kg diet) could moderate the growth suppressing effects, stress and tissue lesions induced by diazinon. In addition, ORG at high dietary levels had toxic effects on fish metabolism. Keywords : Oxidative stress, Organophosphate, Metabolic hormones