en aquaculture aquaculture پژوهشي Orginal research papers <span style="font-size:11pt"><span style="line-height:107%"><span style="text-autospace:none"><span style="font-family:Calibri,sans-serif"><span lang="TR" style="font-size:12.0pt"><span style="line-height:107%"><span new="" roman="" style="font-family:" times=""><span style="color:black">This study was aimed to evaluate the single and combined effects of sodium diformate as an acidifier and bacilli probiotics (<i>Bacillus subtilis</i> and <i>B. licheniformis</i>) on some immunological, oxidative stress and biochemical responses in juvenile <i>Salmo trutta caspius</i> for 60 days. Hundred juvenile fish weighing 12.6&plusmn;1.4 g was divided into 4 different treatments, including control, 0.4 g <i>B. subtilis</i><span style="background:white">+</span><i>B. licheniformis</i> /kg diet, 0.5 g sodium diformate/kg diet and their combination (0.4 g <i>B. subtilis</i> <span style="background:white">+ </span><i>B. licheniformis</i>+0.5 g sodium diformate/kg diet). Blood samples (9 fish/treatment) were withdrawn at two different time intervals (days 30 and 60). Results showed that bacilli probiotics treatment led to significant increases in the serum lysozyme and complement activities (ACH₅₀) at days 30 and 60, and sodium diformate only increased this parameter at day 30 as compared with the control one. The ACH₅₀ indicated a significant decrease following sodium diformate treatment at the same time. Serum bactericidal activity was declined following either acidifier or probiotic treatment. Serum catalase activity was elevated in all treatments, either significant or insignificant as compared with control. Serum malondialdehyde (MDA) was not changed significantly during 30 days of the experiment. On the contrary, bacilli probiotics and sodium diformate led to increase and decrease in MDA, respectively. Our data suggest that sodium diformate applied here was much more successful in improving the fish health status rather than bacilli probiotics. Combined treatment revealed a mid-level of responses except for ACH₅₀, in which a higher level was observed. </span></span></span></span></span></span></span></span> Acidifier, Probiotic, Antioxidant defense, Immunity system, Caspian trout 85 108 http://jifro.ir/browse.php?a_code=A-10-3541-1&slc_lang=en&sid=1 M. Hoseinpouri Ghasemabad Sofla mehdi.doe@gmail.com 100319475328460051270 100319475328460051270 No Department of Fisheries Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran M. Soltani msoltani@ut.ac.ir 100319475328460051271 100319475328460051271 No Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran T. Mohammadian T.mohammadian@scu.ac.ir 100319475328460051272 100319475328460051272 Yes Department of Clinical Sciences, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran M. Shamsaie Mehrgan Mehdi Shamsaei@gmail.com 100319475328460051273 100319475328460051273 No Department of Fisheries Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran