Biochemical responses of common carp, Cyprinus carpio, to transportation in plastic bags using thymol as a sedative agent

The present study aimed at assessing the effects of addition of thymol [0 (T0), 2.5 mg/L (T2.5), 5 mg/L (T5) and 10 mg/L (T10)] to water on biochemical and antioxidant responses of common carp, Cyprinus carpio, during 3-h transportation. The lowest dissolved oxygen and ammonia levels after transportation were related to T2.5 and T5 treatments respectively. T5 treatment exhibited lower cortisol/glucose responses after transportation and 24 h after that, whereas T2.5 and T10 exhibited elevations in these parameters at the same times. Hyperammonaemia and hyperchloraemia were observed in T2.5 treatment immediately after transportation, but such changes were observed in all treatments, 24 h after transportation. Addition of 10 mg/L thymol to water prevented uraemia after transportation, but all thymol-treated fish exhibited uraemia, 24 h after transportation. Thymol treatment failed to mitigate lactate elevation immediately after transportation; nevertheless, T2.5 and T10 had, respectively, the lowest and highest lactate levels, 24 h after transportation. T5 treatment inhibited alteration in superoxide dismutase activity, immediately after transportation, and T10 exhibited a similar effect, 24 h after transportation. Addition of 2.5 mg/L thymol to water significantly increased catalase activity immediately after transportation, but such a response was observed in all treatments, 24 h after transportation. T2.5 and T10 exhibited higher malondialdehyde levels than T0 immediately after transportation, but such a response was observed in all thymol-treated fish, 24 h after transportation. In conclusion, addition of 5 mg/L thymol is beneficial in reducing water ammonia concentration and stress in carp during transportation. © 2021 John Wiley & Sons Ltd