Effect of aqueous extracts of Hypericumperforatum on hemato- serological parameters and survival of rainbow trout (Oncorhynchusmikiss) under thermal stress

A 27 day study was undertaken to evaluate the effects of aqueous extracts of Hypericumperforatum on hemato-serological parameters and survival of rainbow trout (Oncorhynchusmikiss) under thermal stress (20 ± 2 ◦C). A total of 360 rainbow trout (97.2 ± 1.6g) were divided randomly into four groups and immersed in different concentrations (0, 250, 500 and 750 ppm) (T0, T25, T50 and T75) of aqueous extracts of H. perforatum. The blood samples were collected on day 12 and 27 and hemato-serological parameters were determined. In stage 1, the total red blood cell, hemoglobin and hematocrit didn’t show a significant difference among controls and treatments but in stage 2, those parameters were significantly increased in T50 and T75 compared to T0 and T25. The total white blood cell, lymphocytes, total protein, albumin, and total IgM showed a significant increase in treatments compared to control but the results in the neutrophils was opposit. The MCV and MCH didn’t significantly change in two stages but the MCHC of T75 were significantly higher than T0 and T25. The glucose of T50 and T75 were significantly lower than T0 and T25. The hepatic enzymes, ALT and AST of T75 significantly increased compared to other groups in stage2. The highest and lowest survival rates were observed in T50 and T0, respectively. Based on the results, it seems that Hypericumperforatum could control the effectsof stress and increase the survival rate of rainbow trout when exposed to chronic heat stress.