Essential oil of Aloysia citriodora Paláu and citral: sedative and anesthetic efficacy and safety in Rhamdia quelen and Ctenopharyngodon idella.

OBJECTIVE: To verify the efficacy of citral in inducing sedation and anesthesia in silver catfish (Rhamdia quelen) and grass carp (Ctenopharyngodon idella) and to assess the safety of essential oil (EO) of Aloysia citriodora and citral in inducing and maintaining anesthesia in silver catfish. STUDY DESIGN: Clinical study, randomized, parallel, multi-arm with control group in target species. ANIMALS: A total of 96 juvenile and 72 adult silver catfish and 80 juvenile grass carp were used. METHODS: Silver catfish and grass carp were exposed to different concentrations of citral, 15-675 and 15-600 µL L-1, respectively, during the maximum period of 30 minutes to verify sedation and anesthesia induction and recovery times. In addition, for anesthetic induction, silver catfish were exposed to the EO of A. citriodora and citral at 225 µL L-1 for 3.5 minutes. Then, fish were transferred to an anesthesia maintenance solution at 50 µL L-1 for 10 minutes to assess hematologic and biochemical variables at 60 minutes, 2 and 6 days after treatment. RESULTS: Citral only induced sedation from 15, 25 and 40 µLL-1 in both species. Anesthesia without mortality was induced in silver catfish at 50-600 µL L-1 and grass carp at 75-450 µL L-1. At 675 and 600 µL L-1, mortality was recorded in silver catfish and grass carp, respectively. The EO of A. citriodora and citral were safe in inducing and maintaining anesthesia in silver catfish, with mean corpuscular hemoglobin concentration being the only variable that varied in relation to time and treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Citral was effective in inducing sedation and anesthesia in both species. In addition, A. citriodora EO and citral were safe in inducing and maintaining anesthesia in silver catfish. Both agents are promising substances for the development of new drugs for fish.

Anesthesia and anesthetic action mechanism of essential oils of Aloysia triphylla and Cymbopogon flexuosus in silver catfish (Rhamdia quelen).

OBJECTIVES: To document the time for anesthesia induction and recovery using different concentrations of essential oils (EOs) of Cymbopogon flexuosus and Aloysia triphylla in silver catfish (Rhamdia quelen), and to determine whether the mechanism of action of either EO involves the benzodiazepine (BDZ) site of the GABAA receptor. STUDY DESIGN: Experimental study. ANIMALS: A total of 144 silver catfish, length 7.5 ± 1.1 cm, weighing 3.95 ± 0.85 g. METHODS: Essential oils were evaluated at concentrations of 25, 150 and 300 µL L-1, and also ethanol alone (seven groups, n = 6 per group). Induction of sedation or anesthesia and recovery were assessed. In a further six groups (n = 6 per group), fish were exposed to both EOs (25, 150 or 300 µL L-1) with diazepam 150 µm, and also diazepam (10 µm) alone. Flumazenil (5 or 10 µm) was added to the recovery water of fish exposed to diazepam (150 µm) or both EOs (150 and 300 µL L-1) (total of 10 groups = 60 fish). RESULTS: Both EOs induced anesthesia at concentrations of 150 and 300 µL L-1, and sedation at 25 µL L-1. There was no significant difference between EOs for reaching deep anesthesia; there was a significantly longer recovery time for the EO of C. flexuosus. The addition of diazepam (150 µm) resulted in faster induction of anesthesia with both EOs, with no significant change in recovery times. Flumazenil (10 µm) reversed the diazepam-induced anesthesia, but not the anesthesia induced by EOs. CONCLUSIONS AND CLINICAL RELEVANCE: The EO of C. flexuosus induced effective sedation (25 µL L-1) and anesthesia (150 and 300 µL L-1) without short-term mortality. The modulation of the BDZ site of the GABAA receptor in the anesthetic action mechanism of both EOs was not demonstrated.

Using the essential oil of Aloysia triphylla (L'Her.) Britton to sedate silver catfish (Rhamdia quelen) during transport improved the chemical and sensory qualities of the fish during storage in ice.

UNLABELLED: Exposure of silver catfish to 40 µL/L of the essential oil of Aloysia triphylla (AT) during in vivo transport delayed the onset and resolution of rigor mortis as well as the degradation of IMP into HxR compared to the control. The fish that were treated with 30 or 40 µL/L of AT received lower sensory demerit scores after 10 d of storage in ice compared to the control, and the fish that were treated with 40 µL/L of AT had a longer sensory shelf life than did the control. These results indicated that using AT as a sedative in the water in which the silver catfish were transported extended their freshness and increased their shelf life during refrigerated storage. PRACTICAL APPLICATION: Interest in natural anesthetics, such as Aloysia triphylla, has increased in the field of commercial aquaculture because they reduce the number of fish lesions acquired during capture, handling, and transportation. Fish sedated with the essential oil of A. triphylla at 40 µL/L during transport before slaughter exhibited a delay in the loss of freshness and an increased shelf life in ice. In addition to improving animal welfare before slaughter, the essential oil appears to be a promising product for improving fish conservation in the food industry.