Cinnamomum zeylanicum essential oil as an anesthetic and its influence on the physiological parameters of Rhamdia quelen

The objective of this study was to determine the optimal concentration of Cinnamomum zeylanicum essential oil (CZEO) as an anesthetic for Rhamdia quelen and to evaluate the effects of exposure on stress responses. A total of 60 animals (245.75 ± 17.61 g) were used, divided into five treatment groups (140, 160, 180, 200, and 220 μL L-1 of CZEO) and a control group (without CZEO). Additionally, to assess the effects of CZEO exposure on stress responses, 30 animals (200.71 ± 30.18 g) were divided into two treatment groups: Basal (control levels) and CZEO (exposure to 200 μL L-1 of CZEO). Blood samples were collected to measure plasma levels of cortisol, lactate, and glucose. The induction time was significantly shorter (P < 0.05) than three minutes at CZEO concentrations of 180, 200, and 220 μL L-1. The concentration of 200 μL L-1 was considered optimal, as it was the lowest concentration that anesthetized the fish in less than three minutes. No statistically significant differences (P > 0.05) in plasma cortisol and glucose levels were observed between the CZEO and Basal treatments. However, plasma lactate levels were significantly higher (P < 0.05) in the CZEO group compared to the Basal group. No mortality was observed throughout the experiment. In conclusion, 200 μL L-1 of CZEO is safe and effective for use as an anesthetic in R. quelen.