Effects of adding Thymol to water on hematological and immunological parameters of common carp (Cyprinus carpio) during transportation

Various herbal essences have been used in transportation of fish with conflicting results based on their sedative and anti-stress potency. Thymol, a phenolic compound with sedative effects, was used during transportation of common carp (Cyprinus carpio) juveniles in this study. Fish were divided to four groups and 0, 2.5, 5 and 10 mg/l Thymol was added to transportation plastic bags of each group, respectively. The plastic bags were transported for 3 hours. Then, 2 fish were chosen randomly from each bag and blood samples were taken from the caudal vein. WBC and RBC, MCV, MCH, MCHC were measured and percentages of HCT, Neutrophil, Monocyte and Eosinophil were determined. Furthermore, activity of complement, lysozyme and total immunoglobulin were assessed. The results showed that there was no significant difference among the groups contained Thymol and the control group regarding RBC, MCV, MCH, MCHC, Monocytes and Eosinophils after transportation. The lowest Hb and HTC were observed in 5 mg/l thymol group. WBCs, Neutrophils, Lymphocytes, immunoglobulins, lysozymes and complement showed no significant difference in 5 mg/l group, compared to the control group. However, WBCs, Neutrophils, Lysozymes and complement were higher in the 10 mg/l thymol group than the control. Besides, Lymphocytes were lower in 10 mg/l thymol group than the control. It is concluded that adding 5 and 10 mg/l Thymol to the water can, respectively, reduce and increase the transportation stress in common carp.