en fish disease fish disease پژوهشي Orginal research papers This study was carried out to investigate the effect of dietary supplementation of garlic (<em>Allium sativum</em>) extract on growth parameters and hematological parameters and immune system response of <em>Mugil cephalus</em> larvae encountered with <em>Photobacterium damselae</em>. Two hundred and forty <em>M. ceph</em>alus larvae with a mean weight of 5g were randomly divided into 12 equal groups, each containing 3 replicates. Fish were fed with diets containing 50, 100 and 200mg garlic extract/Kg of food for 8 weeks. Based on the results, significant difference was observed comparing final weight, specific growth rate (SGR), daily growth rate (DGR), protein efficiency ratio (PER) and feed conversion ratio (FCR) of 100 and 200mg garlic extract/Kg of food treatments and other treatments (<em>p</em><0.05). Also, in 100 mg garlic extract/Kg treatment, red and white blood cells, hemoglobin, PCV counts, globulin, total protein and albumin were significantly higher than those of control and 200mg garlic extract/Kg of food (<em>p</em><0.05). The immune indices (lysozyme activity, serum total immunoglobulin (Ig) content, phagocytic activity and respiratory burst activity) significantly increased in 100mg garlic extract/Kg treatment compared to those of other treatments, especially control (<em>p<</em>0.05). The results revealed that treatments containing 50 and 100mg garlic extract/Kg food had the highest survival after challenging with <em>P. damselae </em>compared to survival of other treatments (<em>p<</em>0.05)<em>. </em>In conclusion<em>,</em> results suggested that dietary administration of garlic extract; especially in 100mg garlic extract/Kg concentration is recommended for enhancing growth performance, nutritional function, immunity and resistance of <em>M. cephalus</em> larvae against the bacterium<em> P. damselae.</em> Allium sativum, Mugil cephalus, Hematological parameters, Immune response, Photobacterium damselae. 1149 1164 http://jifro.ir/browse.php?a_code=A-10-335-13&slc_lang=en&sid=1 M.J. Zorriehzahra zorrieh@yahoo.com 100319475328460041056 100319475328460041056 No Department of Aquatic Animal Health and Diseases, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran. M. Adel miladadel85@yahoo.com 100319475328460041057 100319475328460041057 Yes Department of Aquatic Animal Health and Diseases, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran. s. Kakoolaki 100319475328460041058 100319475328460041058 No Department of Aquatic Animal Health and Diseases, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran. M. Seidgar 100319475328460041059 100319475328460041059 No National Artemia Research Center, Iranian Fisheries Science Research Institute, Agricultural Research, Education and Extension Organization, Urmia, Iran P. Akbari 100319475328460041060 100319475328460041060 No Department of Marine Sciences, Fisheries Group, Chabahar Maritime University, Chabahar, Iran M.R. Mehrabi 100319475328460041061 100319475328460041061 No Department of Aquatic Animal Health and Diseases, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran. S. Jadgal 100319475328460041062 100319475328460041062 No Offshore Research Center, Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and Extension Organization (AREEO), Chabahar, Iran F. Sakhaie 100319475328460041063 100319475328460041063 No School of Pharmacy, Shahid Beheshti University, Tehran, Iran M.S. Fereidouni 100319475328460041064 100319475328460041064 No Animal Health Units, School of Veterinary Medicine, Shiraz University, Shiraz, Iran