other پژوهشي Orginal research papers <a name="OLE_LINK164"></a><a name="OLE_LINK150">The present study evaluated the effect of <em>Lactobacillus plantarum</em> as a probiotic on the growth performance and haematological parameters of juvenile rainbow trout (<em>Oncorhynchus mykiss</em>) weighing 29.6&plusmn;1.8 g immunized with streptococcus/lactococcus bivalent vaccine for 60 days at 16&plusmn;1.5&ordm;C. Fish were randomly allocated to 4 equal groups: probiotic (g kg^-1 feed equal to 10⁸cells g^-1) supplemented diet group (group P), vaccinated fish fed with a normal diet (group V),</a><a name="OLE_LINK158"></a><a name="OLE_LINK28"> vaccinated fish fed with probiotic</a> (group P+V) and unvaccinated fish fed normal diet (group C). Results showed that weight gain, final weight, condition factor and thermal-unit growth coefficient <a name="OLE_LINK177"></a><a name="OLE_LINK176">were improved in P+V group</a> compared with other groups but was significantly different from groups V and C (<em>p<</em>0.05). Also, feed conversion ratio in the P+V group was lower than other trails (<em>p<</em>0.05). In addition<a name="OLE_LINK208"></a><a name="OLE_LINK207">,</a> white blood cell count (WBC) in groups V and P+V were significantly higher than in both P and C groups (<em>p<</em>0.05). Also, PCV was significantly increased (<em>p<</em>0.05) in both P and P+V groups compared to group V and the control group. No significant difference (<em>p></em>0.05) was found in RBC, Hb, MCH, MCHC and MCV levels among the different experimental groups. These data show that application of <em>L. plantarum</em> could be a benefit of vaccinated trout, enhancing fish growth and haematological parameters Lactobacillus plantarum, probiotic, trout, haematology, growth, vaccine, streptococcosis/lactococcosis 283 295 http://jifro.ir/browse.php?a_code=A-10-776-8&slc_lang=other&sid=1 M. Soltani msoltani@ut.ac.ir 100319475328460029832 100319475328460029832 Yes Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran A. Kane 100319475328460029833 100319475328460029833 No Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran A. Taheri-Mirghaed 100319475328460029834 100319475328460029834 No Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran K. Pakzad 100319475328460029835 100319475328460029835 No Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran P. Hosseini-Shekarabi 100319475328460029836 100319475328460029836 No Departmet of Fisheries Science, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Iran. Departmet of Fisheries Science, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Iran.