Euthanasia is the term used to describe a method of killing that minimizes pain, distress, and anxiety experienced by the animal before loss of consciousness. Techniques used in contexts such as pest control, slaughter, or depopulation may not always meet the criteria of euthanasia due to situational constraints.
Acceptable Techniques for Euthanasia of Animals
Animal slaughter, depopulation, and humane killing are distinguished from euthanasia, because they are performed for reasons different than sparing an animal from unresolvable painful or distressful conditions. Euthanasia of animals is a common procedure performed by veterinary professionals, and because of the seriousness of the action, it deserves appropriate consideration. Some of the most difficult euthanasia decisions that veterinarians are required to make involve the euthanasia of healthy animals when no other alternative for their care can be identified. A veterinarian must be fully prepared to speak frankly about the animal’s condition and be knowledgeable about all possible alternative care resources when interacting with animal owners, caretakers, and control professionals.
Recognizing the importance of a "good death" in the humane termination of an animal’s life, many countries and professional organizations have developed guidelines and recommendations for animal euthanasia; some are more specific for certain species and environmental settings. Most recommendations emphasize certain factors that personnel performing euthanasia should consider when selecting the best method to use:
ability of the method to induce loss of consciousness and death with minimal pain and distress
time required to induce loss of consciousness
reliability
safety of personnel
irreversibility
compatibility with intended animal use and purpose
documented emotional effect on observers or operators
compatibility with subsequent evaluation, examination, or use of tissue
drug availability and human abuse potential
compatibility with species, age, and health status
ability to maintain equipment in proper working order
safety for predators or scavengers should the animal’s remains be consumed
legal requirements
environmental impacts of the method or disposition of the animal’s remains
Euthanizing agents cause death by three basic mechanisms: 1) direct depression of neurons necessary for life function, 2) hypoxia, and 3) physical disruption of brain activity. Because loss of consciousness resulting from these mechanisms can occur at different rates, the suitability of a particular agent or method will depend on whether an animal experiences distress before loss of consciousness. Unconsciousness, defined as loss of individual awareness, occurs when the brain’s ability to integrate information is blocked or disrupted.
Agents and Methods of Euthanasia by Species
Species | Acceptable Methodsa | Acceptable Methods with Conditionsb |
|---|---|---|
Aquatic invertebrates | S6.3c: Immersion in anesthetic solution (magnesium salts, clove oil, eugenol, ethanol) | S6.3: Adjunctive methods (second step) include 70% alcohol and neutral-buffered 10% formalin, pithing, freezing, boiling |
Amphibians | S7.3: As appropriate by species—injected barbiturates, dissociative agents, and anesthetics as specified, topical buffered tricaine methanesulfonate or benzocaine hydrochloride | S7.3: As appropriate by species—inhaled anesthetics as specified, CO2, penetrating captive bolt or firearm, manually applied blunt force trauma to the head, rapid freezing of small (< 4 g [0.1 oz]) individuals where immediate death occurs |
Avian species (see also Poultry, below) | S5: IV barbiturates | S5: Inhaled anesthetics, CO2, CO, N2, Ar, cervical dislocation (small birds and poultry), decapitation (small birds) S7.5: Gunshot (free-ranging birds) |
Cats | S1: IV barbiturates, injected anesthetic overdose, Tributame, T61 | S1: Barbiturates (alternative routes of administration), inhaled anesthetic overdose, COc, CO2c, gunshotc |
Cattle | S3.2: IV barbiturates | S3.2: Gunshot, penetrating captive bolt |
Dogs | S1: IV barbiturates, injected anesthetic overdose, Tributame, T61 | S1: Barbiturates (alternative routes of administration), inhaled anesthetic overdose, COc, CO2c, gunshotc |
Fish | S6.2: Immersion in buffered benzocaine or benzocaine hydrochloride, isoflurane, sevoflurane,quinaldine sulfate, buffered tricaine methanesulfonate, 2-phenoxyethanol, injected pentobarbital, rapid chilling (appropriate species), ethanol | S6.2: Eugenol, isoeugenol, clove oil, CO2-saturated water (aquarium-fish facilities/fisheries), decapitation/cervical transection/manually applied blunt force trauma followed by pithing or exsanguination, maceration (research setting), captive bolt (large fish) |
Equids | S4: IV barbiturates | S 4: Penetrating captive bolt, gunshot |
Marine mammals | S7.5(captive): Injected barbiturates (captive) S7.7 (free-ranging): Injected barbiturates or anesthetic overdose | S7.5 (captive): Inhaled anesthetics (captive) S7.7 (free-ranging): Gunshot, manually applied blunt force trauma, implosive decerebration |
Nonhuman primates | S2.3, S7.4: Injected barbiturates or anesthetic overdose | S2.3, S7.4 (as appropriate by species): Inhaled anesthetic, CO, CO2 |
Poultry | S3.4: Injected barbiturates and anesthetic overdose | S3.4: CO2, CO, N2, Ar, low-atmospheric-pressure stunning, cervical dislocation (as anatomically appropriate), decapitation, manual blunt force trauma, electrocution, gunshot, captive bolt |
Rabbits | S2.4: IV barbiturates | S2.4: Inhaled anesthetic overdose, CO2, cervical dislocation (as anatomically appropriate), penetrating captive bolt, nonpenetrating captive bolt |
Reptiles | S7.3: As appropriate by species—injected barbiturates/buffered tricaine methanesulfonate, dissociative agents with adjunctive method and anesthetics as specified | S7.3: As appropriate by species—inhaled anesthetics as specified, CO2, penetrating captive bolt or firearm, manually applied blunt force trauma to the head, rapid freezing for animals < 4 g where immediate death occurs, spinal cord severance/destruction of brain (crocodilians) |
Rodents | S2.2: Injected barbiturates and barbiturate combinations, dissociative agent combinations | S2.2: Inhaled anesthetics, CO2, CO, tribromoethanol, ethanol, cervical dislocation, decapitation, focused beam microwave irradiation |
Small ruminants | S3.2: Injected barbiturates | S3.2: CO2 (goat kids), gunshot, penetrating captive bolt, nonpenetrating captive bolt (goat kids) |
Swine | S3.3: Injected barbiturates | S3.3: CO2, CO, N2, Ar, gunshot, electrocution, penetrating captive bold, nonpenetrating captive bolt (piglets), manually applied blunt force trauma |
Reprinted, with permission, from the AVMA Guidelines on Euthanasia 2020 Edition. Note: Initial “S” references with associated numbers in table entries refer to specific areas of more detailed information in the AVMA guidelines, available at www.avma.org/sites/default/files/2020-02/Guidelines-on-Euthanasia-2020.pdf. a Acceptable methods are those that consistently produce a humane death when used as the sole means of euthanasia. b Acceptable methods with conditions are those that may require certain conditions to be met to consistently produce humane death, may have a greater potential for operator error or safety hazards, are not well documented in the scientific literature, or may require a secondary method to ensure death. c Not recommended for routine use. | ||
Ideally, euthanasia techniques cause rapid loss of consciousness, followed by cardiac or respiratory arrest and death. This may occur very rapidly in a technique, such as gunshot targeting the brain, or more gradually, with a method that first induces unconsciousness, such as anesthetic overdose. If loss of motor or respiratory and cardiac function precedes loss of consciousness, as might be the case if paralytic agents are used, animals may become fearful and experience distress, which is not acceptable.
For a list of acceptable methods and agents for euthanasia of different species of animals, see the accompanying table . The full AVMA Guidelines for Euthanasia 2020 provide information necessary to correctly select and implement these techniques.
The Context for Euthanasia of Animals
In most cases, the euthanasia of an animal occurs in a context with:
prior communication and decision making
planning for the euthanasia
staging and conducting the euthanasia
disposition of the remains
The emotional attachment between animals and their owners or caretakers requires an additional layer of professional respect and care. Discussing euthanasia openly allows everyone the opportunity to understand that the best interests of the animal, owners, and caretakers have been considered.
Veterinary professionals may have unfavorable experiences concerning the end of life resulting from conflict with clients, moral stress relating to participation and outcomes, internalizing the client’s grief, negative input from others, and lack of mental health support. Important mitigating factors are: 1) supportive practice policies with compassionate leadership, and 2) training in communication and deliberative frameworks. Early intervention for personnel experiencing unresolved stress or mental health problems is imperative.
It is important that euthanasia is provided in a manner that minimizes distress to the animal and considers their natural behavior. A euthanasia approach that can be applied in familiar surroundings may help reduce distress. For animals accustomed to human contact, gentle restraint (preferably in a familiar and safe environment), careful handling, and talking during euthanasia often have a calming effect and may also be effective coping strategies for personnel and animal owners. Sedation and/or anesthesia may help to achieve the best conditions for euthanasia. It must be recognized that sedatives or anesthetics given at this stage that change circulation may delay the onset of the euthanasia agent.
Death must be confirmed before disposal of any animal remains. A combination of criteria is most reliable in confirming death, including:
lack of pulse, breathing, corneal reflexes and response to firm toe pinch
inability to hear respiratory sounds and heartbeat by use of a stethoscope
graying of the mucous membranes
rigor mortis
None of these signs alone, except rigor mortis, confirms death. Confirming death may best be accomplished by an adjunctive method (eg, thoracotomy, decapitation) performed after the loss of consciousness. Using an adjunctive method may be especially important when euthanizing ectothermic animals, because their heartbeat and respiration are difficult to assess. Animal remains must be disposed of in a legal manner that does not contaminate food sources or the environment.
Key Points
The euthanasia process should minimize or eliminate pain, anxiety, and distress before loss of consciousness.
Acceptable euthanasia techniques vary by species, age, and health status of the individual animal.
Euthanasia can be distressing for owners and veterinary professionals. This should be managed through open dialogue, compassion, and availability of mental health resources.
Death must be confirmed before disposal of any animal remains.
Animal remains must be disposed of in a legal manner that does not contaminate food sources or the environment.
For More Information
Also see pet health content on pet loss and grief.
Click here for more information on the impact of euthanasia on pet owners and veterinarians
AVMA also provides detailed guidelines on euthanasia for various animal species.
