Effectiveness and safety of clove oil and common salt in the long-term transport of Cyprinus carpio

In this study, we aimed to evaluate the effectiveness and safety of clove essential oil (CEO) in combination with common salt during the long-term transport (24 h) of Cyprinus carpio. The experiment was conducted according to a completely randomized design with a 4 x 2 factorial arrangement, including four levels of CEO (0, 5, 10, and 15 mg L-1) and two levels of common salt (0 and 3 g L-1). Sampling was carried out before, immediately after, and 96 h after transport. CEO alone was not completely safe for C. carpio during transportation, as indicated by the increase in unionized ammonia in water and oxidative stress in fish gills and liver. Although common salt reduced water ammonia and fish stress responses (blood glucose), its use in isolation is not recommended, as it caused oxidative damage to the liver and gills. These effects had not been previously reported in the literature. However, the use of 5 mg L-1 CEO in combination with salt provided the best results both immediately after and 96 h after transport. In gills, there was a reduction in nitric oxide and carbonylated proteins and an increase in catalase activity at 96 h after transport. In the liver, there was a decrease in nitric oxide and oxidative damage (carbonylated proteins and malondialdehyde) immediately after transport, as well as a decrease in nitric oxide and an increase in glutathione-S-transferase activity at 96 h after transport. Thus, combined use of 5 mg L-1 CEO and 3 g L-1 common salt proved to be effective and safe, resulting in better maintenance of water quality (lower ammonia content) and redox status of the gills and liver in C. carpio during long-term transport.