The spearmint extract L-carvone as a euthanasia agent in sheep

Area of Science:

• Veterinary Anesthesiology
• Toxicology
• Pharmacology

Background:

• L-carvone, a natural monoterpene from spearmint, is explored for its potential anesthetic and euthanasia applications.
• Previous studies suggest L-carvone can be used for intravenous euthanasia in rats.

Purpose of the Study:

• To investigate the rapid effects of intravenous L-carvone on consciousness and mortality in sheep.
• To determine tissue L-carvone concentrations following intravenous administration for euthanasia.

Main Methods:

• Five adult ewes underwent jugular catheterization; a sixth had inadvertent carotid arterial catheterization.
• Physiological parameters including electroencephalography (EEG), electrocardiogram (ECG), and behavioral monitoring were recorded.
• A 50% food-grade L-carvone solution was administered intravenously at 0.5 mL/kg, followed by tissue analysis using liquid chromatography-mass spectrometry.

Main Results:

• Intravenous L-carvone rapidly induced loss of responsiveness, shallow breathing, and reduced heart rate within seconds.
• Pulses became undetectable within 20 seconds, with apnea and cessation of cardiac electrical activity occurring around 46-48 seconds.
• EEG showed decreased spectral edge frequency and polyspike waves, indicative of altered consciousness and seizure activity.

Conclusions:

• Intravascular L-carvone causes rapid unconsciousness and death in sheep without contaminating the carcass with non-food residues.
• The observed myoclonus and EEG seizure activity suggest L-carvone may not be ideal as a sole euthanasia agent.
• Further research is needed to optimize L-carvone's use in animal euthanasia, potentially in combination with other agents.