M. Soltani - Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
A. Kane - Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
A. Taheri-Mirghaed - Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
K. Pakzad - Department of Aquatic Animal Health, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran
P. Hosseini-Shekarabi - Departmet of Fisheries Science, Faculty of Agriculture and Natural Resources, Science and Research Branch, Islamic Azad University, Tehran, Iran.

The present study evaluated the effect of Lactobacillus plantarum as a probiotic on the growth performance and haematological parameters of juvenile rainbow trout (Oncorhynchus mykiss) weighing ۲۹.۶±۱.۸ g immunized with streptococcus/lactococcus bivalent vaccine for ۶۰ days at ۱۶±۱.۵ºC. Fish were randomly allocated to ۴ equal groups: probiotic (g kg-۱ feed equal to ۱۰۸ cells g-۱) supplemented diet group (group P), vaccinated fish fed with a normal diet (group V), vaccinated fish fed with probiotic (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 were improved in P+V group compared with other groups but was significantly different from groups V and C (p<۰.۰۵). Also, feed conversion ratio in the P+V group was lower than other trails (p<۰.۰۵). In addition, white blood cell count (WBC) in groups V and P+V were significantly higher than in both P and C groups (p<۰.۰۵). Also, PCV was significantly increased (p<۰.۰۵) in both P and P+V groups compared to group V and the control group. No significant difference (p>۰.۰۵) was found in RBC, Hb, MCH, MCHC and MCV levels among the different experimental groups. These data show that application of L. plantarum could be a benefit of vaccinated trout, enhancing fish growth and haematological parameters

Lactobacillus plantarum, probiotic, trout, haematology, growth, vaccine, streptococcosis/lactococcosis