en تخصصي Special پژوهشي Research <p><strong>Background:</strong> Contamination of feeds with cadmium leads to oxidative stress in vital tissues such as gills and affects the fish survival. Therefore, an increase in the capacity of the antioxidant defense system and detoxification system of fish may reduce adverse effects of pollutants. This study investigated the protective effects of microalga <em>Spirulina platensis</em> against oxidative stress in gills of cadmium-treated rainbow trout.</p> <p><strong>Methods:</strong> This study was conducted at Fish Farm, Almas-Dime Village, Koohrang, Charmahal & Bakhtiari Province, Iran from April to July 2016. Rainbow trout were allocated into five groups of which one group received normal feed and served as control. Fish from group II received 0.2 mg CdCl₂ per 1 kg feed. Groups III-V were fed with enriched diet with 2.5, 5 and 10 g <em>S. platensis</em> per 1 kg feed, respectively and simultaneously treated with 0.2 mg kg^-1 CdCl₂for 21 d. Changes in biochemical parameters including alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH), malondialdehyde (MDA) as marker of lipid peroxidation and cellular total antioxidant capacity were evaluated.</p> <p><strong>Results:</strong> Oral exposure to CdCl₂caused a significant increase in MDA levels and altered AST, ALT, ALP and LDH activities in gills (<em>P</em><0.05). The cellular antioxidant capacity was significantly lowered in CdCl₂-treated fish as compared to the control group (<em>P</em><0.05). Oral administration of <em>S. platensis</em> significantly ameliorated these changes in certain biochemical parameters in gills of CdCl₂-treated fish.</p> <p><strong>Conclusion:</strong> The findings indicate that S. platensis has protective effects against toxic influence of CdCl₂ on certain biochemical parameters in gills of fish.</p> Cadmium, Microalga, Biochemical parameter, Oxidative stress Biochemical Parameter, Cadmium, Microalga, Oxidative Stress 5 12 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-88-9&slc_lang=en&sid=1 Hamid Evaz-Zadeh Samani 10031947532846006310 10031947532846006310 No Department of Aquaculture, Behbahan KhatamAlanbia University of Technology, Behbahan, Iran. Mahdi Banaee banaee@bkatu.ac.ir 10031947532846006311 10031947532846006311 Yes Department of Aquaculture, Behbahan KhatamAlanbia University of Technology, Behbahan, Iran. Parvaneh Shoukat 10031947532846006312 10031947532846006312 No Department of Aquaculture, Behbahan KhatamAlanbia University of Technology, Behbahan, Iran. Ahmad Noori 10031947532846006313 10031947532846006313 No Department of Aquaculture, Hormozgan University, Bandar Abbas, Iran. Laleh Mousavi Dehmoredi 10031947532846006314 10031947532846006314 No Department of Aquaculture, Behbahan KhatamAlanbia University of Technology, Behbahan, Iran.