en aquaculture aquaculture پژوهشي Orginal research papers The purpose of this study is to evaluate the effects of Sodium diformate (NDF) and Formic acid salt on the growth performance, nutrition indices, innate immune system, and digestive enzymes activity of 420 <em>Huso huso</em> (30.55&plusmn;1.72 g) were randomly divided into seven experimental treatments. All groups were fed with the experimental diets for 60 days. The experimental diets contained 0.05<span dir="RTL">%</span>, 0.1<span dir="RTL">%</span> and 0.15% NDF and 0.05<span dir="RTL">%</span>, 0.1<span dir="RTL">%</span> and 0.15% Formic acid. Diet control was without any Acidifier. Results show that the best FCR and SGR were observed in the group fed with 0.1% supplemented food by NDF and formic acid (<em>p</em><0.05) on the 30_th and 60_th day , respectively. The results show that the immunological parameters including total immunoglobulin (by 0.1% NDF), serum bactericidal activity (by 0.1 %NDF and 0.1 %Formic acid), and lysozyme activity (by 0.05 and 0.1% NDF) were affected significantly by Acidifier (<em>p</em><0.05). The highest activity of trypsin and chymotrypsin was significant in groups 0.1 % supplemented food by NDF (<em>p</em>˂0.05) in the first 30 days. It can be concluded that the addition of 0.1% of NDF to beluga diets improves growth parameters decreases FCR, increases immunity levels and digestive enzymes activity. <span dir="RTL"></span> Acidifier, Huso huso, Growth performance, Immune parameters, Digestive enzymes activity 879 900 http://jifro.ir/browse.php?a_code=A-10-1694-1&slc_lang=en&sid=1 A. Jedi Mostafaloo A.jedi@scu.ac.ir 100319475328460040349 100319475328460040349 No Department of Fisheries, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran M. Hedayatifard persiafish@gmail.com 100319475328460040350 100319475328460040350 Yes Department of Fisheries, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran M. Keshavarz M.keshavarz@scu.ac.ir 100319475328460040351 100319475328460040351 No Department of Fisheries, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran T. Mohammadian tak.mohammadian@gmail.com 100319475328460040352 100319475328460040352 No Department of Clinical Sciences, College of Veterinary Medicine Shahid Chamran University of Ahvaz, Ahvaz, Iran