Euthanasia refers to ending the life of an animal in a manner that minimizes pain, distress, and anxiety before loss of consciousness.
Veterinarians and other professionals licensed to perform euthanasia can select the method or technique that best aligns with the available supplies, the signalment and health of the animal, and their skill to carry out the procedure successfully. Careful attention to humane technique will prevent dysthanasia (bad death), thus protecting the welfare of the animal during its death.
Other methods of ending life, such as those involved in pest control, slaughter, or depopulation, may not always meet the definition of euthanasia due to situational constraints and are not covered in this section.
Criteria for a Good Death in Animals
Euthanasia of animals is a common procedure performed by veterinary professionals. Nevertheless, because of the seriousness of the action, it deserves appropriate consideration.
Humanely terminating life in a safe and effective manner requires an understanding of the relevant physiology and anatomy in the particular species.
Many countries and professional organizations have developed guidelines and recommendations for animal euthanasia, such as the AVMA Guidelines for the Euthanasia of Animals: 2020 Edition. Some euthanasia guidelines are more specific for certain species and environmental settings, while others attempt to provide broad guidance.
Most recommendations emphasize that, when selecting the best method to use, personnel performing euthanasia should consider certain factors:
ability 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
Acceptable Techniques for Euthanasia of Animals
Death from euthanasia can be achieved through one of the following basic mechanisms:
direct depression of neurons necessary for life function (eg, barbiturate injection)
hypoxia (eg, exsanguination)
physical disruption of brain activity (eg, gunshot)
All euthanasia methods work via one of these mechanisms. It is the veterinarian's responsibility to determine which method is best given the circumstances.
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 (ie, loss of individual awareness) occurs when the brain’s ability to integrate information is blocked or disrupted.
Barbiturates, such as pentobarbital sodium, are the most common euthanasia agents in the US and many other countries. Barbiturates are fast and effective when properly administered and can be used in many species. They work by first rendering the animal unconscious, followed soon after by respiratory and cardiac arrest. The dose and time to death depend on where the drug is administered in the body and on what species is being euthanized. Barbiturates are never administered to food animals.
Pearls & Pitfalls
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For a list of acceptable methods and agents for euthanasia of different species of animals, see the table Agents and Methods of Euthanasia by Species. The full AVMA Guidelines for Euthanasia of Animals provide information necessary to correctly select and implement these techniques.
Agents and Methods of Euthanasia by Species
Species | Acceptable Methodsa | Acceptable Methods With Conditionsb |
|---|---|---|
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 |
Aquatic invertebrates | S6.3: Immersion in anesthetic solution (magnesium salts, clove oil, eugenol, ethanol)c | S6.3: Adjunctive methods (second step) include 70% alcohol and neutral-buffered 10% formalin, pithing, freezing, boiling |
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 | S4: 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 bolt, nonpenetrating captive bolt (piglets), manually applied blunt force trauma |
Adapted, with permission, from the AVMA Guidelines for the Euthanasia of Animals: 2020 Edition. Note: Initial “S” references with associated numbers in table entries refer to specific areas of more detailed information in the AVMA guidelines: www.avma.org/sites/default/files/2020-02/Guidelines-on-Euthanasia-2020.pdf aAcceptable methods are those that consistently produce humane death when used as the sole means of euthanasia. bAcceptable 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. | ||
Adjunctive Methods of Euthanasia of Animals
Although not suitable as a sole or primary means of euthanasia, an adjunctive method (eg, thoracotomy, decapitation) may be performed after loss of consciousness to help ensure death in some cases. Using an adjunctive method can be especially important when euthanizing ectothermic animals (eg, fish, reptiles), because their heartbeat and respiration are difficult to assess.
The Context for Euthanasia of Animals
In most cases, euthanasia of an animal occurs in a context with the following features:
prior communication and decision making
planning for euthanasia
staging and conducting euthanasia
disposition of remains
A veterinarian must be ready to speak honestly about an animal's condition and be knowledgeable about all medical options, including euthanasia.
The emotional attachment between animals and their owners or caretakers demands the utmost 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.
Preplanning details, such as who can be present, where euthanasia will take place, and body disposition options, will help owners feel better prepared. The goal is to ensure a pain-free death, with owners present for the entirety of the procedure if that is their choice.
It is important to provide euthanasia in a manner that minimizes distress to the animal and considers their natural behavior. A euthanasia approach that can be applied in familiar surroundings is ideal. 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 or anesthesia might help to achieve the best conditions for euthanasia. However, sedatives or anesthetics can also alter circulation and delay the onset of the euthanasia agent. Some euthanasia techniques (eg, intracardiac injection with a barbiturate) require anesthetics or physical stunning to induce unconsciousness before death occurs, preventing pain and distress for the animal. Examples of pre-euthanasia sedatives and anesthetics include opioids, phenothiazines, benzodiazepines, alpha-2-adrenergic receptor agonists, and dissociative drugs.
Confirmation of Death After Euthanasia of Animals
Death must be confirmed before disposal of any animal remains. A combination of criteria is most reliable in confirming death:
lack of pulse, breathing, corneal reflexes, and response to painful stimulation
lack of audible heartbeat heard by use of a stethoscope
graying of mucous membranes
rigor mortis
Except for rigor mortis, none of these signs alone confirms death.
Disposal of Animal Remains After Euthanasia
Animal remains must be disposed of in a legal manner that prevents contamination of food sources or the environment. Any animal intended for food should not be euthanized with a barbiturate.
Owners may be informed about disposition options, such as burial, cremation, alkaline hydrolysis, rendering, and other authorized local disposal methods.
Psychological Well-Being of Human Participants During Euthanasia of Animals
Veterinary professionals can encounter challenging experiences resulting from conflict with owners, moral stress relating to participation and outcomes, negative input from others, and lack of mental health support.
Important mitigating factors include supportive practice policies with compassionate leadership and training in communication and deliberative frameworks. Early intervention for personnel experiencing unresolved stress or mental health problems is imperative.
Euthanasia's relief of animal suffering can actually have a positive effect on the mental health of veterinary personnel, especially when the procedure is properly performed.
Key Points
The euthanasia process should minimize or eliminate an animal's pain, anxiety, and distress before loss of consciousness.
Acceptable euthanasia techniques vary by an animal's species, age, and health status.
Personnel should be properly trained in euthanasia techniques.
Euthanasia can be distressing for owners and veterinary professionals; open dialogue, compassion, and availability of mental health resources can help.
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
Appendix 3: making a decision about euthanasia. AVMA Guidelines for the Euthanasia of Animals: 2020 Edition.
Cooney KA, Chappell JR, Callan RJ, Connally BA. Veterinary Euthanasia Techniques; A Practical Guide. Wiley-Blackwell; 2012.
Marchitelli B, Shearer T, eds. Small animal euthanasia; updates on clinical practice. Vet Clin North Am Small Anim Pract. 2020;50(3).
Cooney K. Euthanasia protocols. Clinician's Brief.
Cooney K. What's behind a good pet euthanasia? Companion Animal Euthanasia Training Academy.
See more on the impact of euthanasia on pet owners and veterinarians.
Also see pet owner content on pet loss and grief.
