Potencial anestésico e sedativo do óleo essencial de Cymbopogon citratus em juvenis de Tambaqui Colossoma macropomum

Abstract

The use of substances such as essential oils with anesthetic potential has intensified in aquaculture. Some of them have been tested as reducing stress during transport, and are considered safe, viable alternatives that can improve fish welfare. In this study the objective was to evaluate the anesthetic and sedative potential of Cymbopogon citratus essential oil (EOCC) in juvenile tambaqui (Colossoma macropomum). The Thesis consists of two chapters where, in the first, different concentrations of OECC were evaluated for anesthetic induction and recovery in tambaqui (experiment 1) and its effects on biochemical parameters and oxidative stress were verified at different recovery times (experiment two). In experiment 1, the fish were exposed to different concentrations of essential oil (60, 80, 100, 120 mg/L), in addition to the alcohol control for anesthetic induction and recovery tests. In experiment 2, tambaqui juveniles (N= 48, 10.06 ± 0.31cm and 9.9 ± 0.38 g), were subjected to biometry under deep anesthesia at the best concentration obtained in experiment 1 (100 mg/L EOCC) and control group (water only). After 0, 30, 60 and 120 minutes of recovery, the fish were euthanized and tissues were collected for biochemical and oxidative stress analyses. The main results indicate that the increasing concentration of essential oil proportionally decreased the time for anesthetic induction. There was no significant difference in recovery time between the oil concentrations used. Concentrations of 100 mg/L and 120 mg/L of OECC showed better times for anesthetic induction in tambaqui juveniles (161 seconds = 2.68 minutes and 170.5 seconds = 2.84 minutes), respectively. The alcohol control did not produce an anesthetic or sedative effect. EOCC did not cause mortality in animals exposed to essential oil in anesthetic induction tests, and generally improved metabolic and oxidative stress parameters, stimulated the antioxidant activity of substances such as Superoxide dismutase (SOD) and Reduced Glutathione (GSH) in tissues , with lower levels of thiobarbituric acid reactive substances (TBARS). In the second chapter, the use of OECC as a sedative was evaluated in simulated conditions of transport of tambaqui juveniles for 17 hours. The juveniles were placed in 10 L plastic bags (10 juveniles/L or 20 juveniles/bag) and pure oxygen, in three concentrations of OECC (8, 10 and 12 mg/L), and the EOCC was diluted in ethanol ( 1:10), in addition to the water control and alcohol control groups. The main results indicate that there was no mortality at 0 and 24 h after transport (p>0.05) between treatments. The use of OECC 8 mg/L in transport reduced ammonia excretion, loss of Cl- and K+ ions and presented lower glycemic levels in the muscle, and with 12 mg/L it reduced lactate and triglycerides. Furthermore, it was possible to observe better antioxidant conditions with the use of EOCC, verified by the increase in the activity of SOD antioxidant enzymes, in response to the increase in lipoperoxidation levels. The use of EOCC at concentrations of 8 and 100 mg/L is recommended for juvenile tambaqui in long-term transport 17h and rapid handling, respectively.