(See comments after chart for specific information)

The following methods of euthanasia are divided into two general categories - those approved unconditionally by the American Veterinary Medical Association (AVMA) Guidelines on Euthanasia, June 2007 (formerly the 2000 AVMA Panel on Euthanasia) and those conditionally approved.  For methods conditionally approved, adequate scientific justification must be provided at the time of protocol submission consistent with the requirements of the regulations of the Animal Welfare Act and the Public Health Service (PHS) Policy on the Humane Care and Use of Laboratory Animals. 

Generally speaking, an appropriate means of euthanasia is one that meets the following criteria: 1) It renders the animal unconscious painlessly and without distress prior to death; 2) It is performed out of sight, sound, and smell of other conscious animals; 3) It is rapid; 4) It is aesthetically acceptable; 5) It is consistent with both the requirements of the research activity and the skill of the investigator.  In all cases death must be confirmed by observing the animal for the absence of respirations and heart beat. Personnel performing physical means of euthanasia must be well trained.

Please feel free to contact the CMU office at X-6555 or at (330) 325-6555 for additional information regarding these and other means of euthanasia and to arrange for training.

¹See Carbon Dioxide below

²See Inhalant Anesthetics below

GUIDELINES FOR INDIVIDUAL EUTHANASIA METHODS

Carbon Dioxide

Carbon dioxide can be used from compressed gas cylinders. Animals are usually placed in an enclosed container (e.g., a bell jar or specially designed euthanasia chamber) in which CO₂ displaces the ambient air.  Since CO₂ is heavier than air it accumulates in the bottom of the container, and euthanasia is most rapid if the animals are confined in the lower portion of the container.

If the animals are placed in the chamber before filling with CO₂, then the flow rate for the gas should be adjusted to displace approximately 20% of the chamber volume per minute.  The sound generated by the rapidly expanding gas can be such that it is distressful to the animals, so attempts should be made to muffle the noise. If animals are placed in a chamber that has been prefilled with at least 70% CO₂, unconsciousness is induced more rapidly and the issue of noise is avoided.

Neonatal animals require prolonged exposure to CO₂ and it may be necessary to use an additional means to confirm death (e.g., decapitation under CO₂ anesthesia).

Cervical Dislocation

Cervical dislocation is suited for poultry and other small birds, mice and rats < 200 grams.  Since there exists some uncertainty about the animal's perception of pain during this procedure, its use in unanesthetized animals requires scientific justification.  Animals can be euthanized by cervical dislocation under anesthesia without scientific justification.

As with other physical means of euthanasia, training and experience are essential to the rapid induction of unconsciousness and the successful performance of euthanasia by this technique.  For those unfamiliar with this technique, please contact the CMU at X-6555 or at (330) 325-6555 for training.

For mice, the animal is placed on a flat surface, restrained by the base of the tail in one hand while the thumb and first two fingers of the other hand restrain the head.  The first finger of the hand restraining the head is placed immediately behind the skull and the tail is used to rapidly elevate the body and pull it back while simultaneously thrusting the finger down to dislocate the cervical vertebrae.  Alternatively, a sturdy rod of approximately 0.75 cm diameter can be placed behind the head in place of the hand restraint of the head.  Cervical dislocation is accomplished by elevating the body as described while pressing down with the rod.

Decapitation

Decapitation is usually accomplished using a commercially available guillotine and is most frequently used with small rodents such as rats.  The procedure is generally regarded as aesthetically unpleasant, but it is an important method of euthanasia in those projects in which it is important to collect unadulterated tissue.  As with cervical dislocation, its use in unanesthetized animals requires scientific justification as a part of the protocol review process.

Decapitation can be performed in amphibians and reptiles using heavy sheers, however it must be followed by pithing and requires scientific justification.

The blades of the guillotine or shears must be maintained in a sharp condition.

Euthanasia Solution

Most commercially available euthanasia solutions contain a high concentration of pentobarbital in propylene glycol and isopropyl or ethyl alcohol.  They are administered by the intravenous route for those species with accessible veins (e.g., cats, rabbits, dogs, pigs, sheep).  For rodents and other small mammals, they can be administered by intraperitoneal injection.  The intracardiac route can be used only in fully anesthetized or unconscious animals.  The usual dose is 1 ml per 10 pounds of body weight; however, the manufacturer's instructions should be followed.

Exsanguination

Exsanguination is often used where it is necessary to collect large volumes of blood from an animal. Exsanguination is approved only in fully anesthetized animals.

Inhalant Anesthetic Agents

In order of preference, halothane, enflurane and isoflurane are acceptable for euthanasia.  For small animals (e.g., laboratory rodents and bats) administration in an enclosed chamber is suitable. For larger species inhalants should be administered with a vaporizer.

When using inhalants in neonatal animals it may be necessary to use an additional means of euthanasia to confirm death (e.g., decapitation or exsanguination under anesthesia).

Ether and methoxyflurane are conditionally acceptable. 

Pentobarbital

Overdoses of pentobarbital are commonly used for euthanasia.  Like the commercially available euthanasia solutions it is best given intravenously, although the intraperitoneal route is suitable for rodents and other small mammals. The intracardiac route can be used only in fully anesthetized or unconscious animals.  The dose for euthanasia should be 120 mg/kg or greater.  As for any method of euthanasia, death must be confirmed before disposal.

Pithing

Generally pithing is considered an adjunctive method of euthanasia suitable only for certain amphibians and reptilian species.  For frogs, double pithing is conditionally acceptable.  For other species, pithing must be accompanied by another means to achieve euthanasia.