¹Department of Fisheries, Faculty of Natural Resources, Urmia University, Urmia, IRAN
²Department of Food Hygiene and Quality Control, Faculty of Veterinary Medicine, Urmia University, Urmia, IRAN
³Department of Microbiology, Faculty of Veterinary Medicine, Urmia University, Urmia, IRAN
⁴Department of Clinical Science, Faculty of Veterinary Medicine, Shahid Chamran University, Ahvaz, IRAN
⁵Department of Aquaculture & Quality Control, Artemia & Aquaculture Institute, Urmia University, Urmia, IRAN DOI : 10.9775/kvfd.2017.18973 This study was conducted to determine the effect of Salvia officinalis (Sage) and Aloe vera (Barbados aloe) as immunostimulators on immune indices of Rainbow trout (Oncorhynchus mykiss) and resistance against Streptococcus iniae infection. A total of 945 rainbow trout (10±0.1 g) randomly distributed into seven groups with three replicates, were fed with 0 (control), 0.5, 1 and 1.5% of food S. officinalis and A. vera hydroethanolic extracts for 30 days. All fishes were fed with control diet for 15 next days. Total WBC, WBC drift, complement activity, lysozyme activity and total immunoglobulin were measured at 30th and 45th days of the trial. At days 30 and 45 samples from all trial groups were injected with S. iniae (3.66×108 CFU mL-1), and their mortality was recorded at the end of next ten days period. Results showed that A. vera could significantly (P<0.05) increase total WBC, lymphocyte, neutrophil, complement activity, lysozyme activity and total Immunoglobulin in comparison to the control group. S. officinalis had no significant (P<0.05) effect on parameters under study except total Immunoglobulin at rate of 1.5%. Also A. vera (1.5%) decrease mortality and improves rainbow trout resistance against S. iniae beside control group significantly (P<0.05). Based upon findings of this study, A. vera ethanolic extract can enhance immune responses and improve resistance of rainbow trout against S. iniae infection and it can be used to replace synthetic immunostimulators for rainbow trout. Keywords : Rainbow trout, Aloe vera, Salvia officinalis, S. iniae, Immune responses