General

Table of Euthanizing Methods (All Species)

Approved Euthanasia Methods for Rats, Mice, Hamsters, Guinea Pigs and Other Rodents:

Carbon Dioxide

Euthanasia by use of general anesthesia

Physical Methods of Euthanasia

• Cervical Dislocation
• Decapitation

Barbiturates

• Table of barbiturate euthanizing doses

Table of euthanizing methods (all species)

Approved Euthanasia Methods for Rabbits:

Euthanasia by use of general anesthesia

Barbiturates

• Table of barbiturate euthanizing doses

Table of euthanizing methods:

• Rodents/Rabbits <125 gm
• Rodents/Rabbits > 125 gm and < 1 kg
• Rodents/Rabbits > 1 kg but < 5 kg
• Dogs and Cats
• Farm Animals
• Avian Species
• Nonhuman primates

General:

The NIH Guide defines euthanasia as "the procedure of killing animals rapidly and painlessly". University of Iowa euthanasia guidelines, summarized in the table of methods follow those established by the American Veterinary Medical Association Panel on Euthanasia. Euthanasia techniques must be reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) during review and approval of the Animal Care and Use Review Form.

Euthanasia must be carried out by personnel properly trained in the procedure being used. While decapitation and cervical dislocation may be humane when administered by properly trained personnel, animal use protocols proposing these techniques without sedation or anesthesia must include the scientific rationale justifying this exclusion. Measures should be taken to ensure that euthanasia is performed in a way that minimizes reactions among other animals that may be present.

Gentle, careful handling of subject animals is of the utmost importance during the procedure in order to minimize distress to the animal, as well as to the operator. An unconscious animal does not perceive pain. Appropriately conducted procedures which render the cerebral cortex nonfunctional by means such as hypoxia or drug induced anesthesia eliminate perception of pain. Reflex motor activity may be present in an animal with a nonfunctional cerebral cortex, but pain is not perceived.

Proper euthanasia technique includes a follow-up exam to confirm the absence of a heartbeat, which is a reliable indicator of death. Monitoring respiration is not considered sufficient since with some euthanasia techniques heartbeat may be maintained after visible respiration has ceased. Decapitation, cervical dislocation or thoracotomy should be used after administration of euthanatizing drugs to insure that animals do not revive. A physical method of euthanasia must be performed on all large animal species (e.g. rabbit) after the administration of an euthanatizing agent. 

The need to minimize fear and apprehension must be considered in determining the method of euthanasia. Distress vocalizations, fearful behavior, and release of certain odors or pheromones by a frightened animal may cause anxiety and apprehension in other animals. Therefore, whenever possible, animals should not be exposed to euthanasia of others, especially of their own species. The resultant distress may lead to physiologic changes in other animals, such as a release of hormones, which may effect research results. The acceptable methods of euthanasia vary aesthetically. Personnel's perception must often be considered in addition to experimental requirements when a method of euthanasia is chosen.

The following are methods and procedures which are accepted by the IACUC for humane killing of animals. In general these are the same as recommendations of the American Veterinary Medical Association (AVMA) Panel on Euthanasia, 2000. Methods other than those generally approved may be approved with adequate justification based on scientific need and demonstration that the method chosen produces the minimum amount of animal pain and distress consistent with experimental requirements. Also included is a list of unacceptable methods deemed inhumane or dangerous to personnel and to other animals.

Many of the approved methods of euthanasia require technical proficiency for proper conduct and should not be attempted without prior training (e.g., intravascular injections and physical methods). Other methods, such as carbon dioxide inhalation and electrocution, may only be used with properly designed equipment. Trained personnel in the OAR (Office of Animal Resources) are available to perform or assist in the performance of animal euthanasia.

Approved Animal Euthanasia Methods for Rodents

Carbon dioxide inhalation can be suitable for all species, provided acceptable equipment is used. Practically, its use is limited to rodents and other mammals weighing less than about 500 grams. Compressed CO2 from cylinders is the only acceptable source. Dry ice is no longer permitted as a CO2 source.

Chamber method - This method employs a top-opening chamber into which the animal(s) are introduced . After the animal(s) are placed in the chamber, a slow flow of CO2 is intiated for a few minutes to slowly establish a high concentration at the bottom of the chamber.  It is an unacceptable practice to pre-charge the chamber with CO2 prior to placing the animals in the chamber.

After breathing has stopped and the animal(s) are unconscious, euthanasia may be completed by any of the following procedures:

• continued exposure to CO2 for 15-30 minutes after breathing has stopped (newborn of most species are more resistant than adults to CO2 and will require exposure times 2-3 times as long to assure death.);
• exsanguination;
• cervical dislocation;
• thoracotomy
• administration of injectable anesthetic or euthanasia preparation.

Euthanasia by use of general anesthesia

Induction of general anesthesia followed by death without regaining consciousness is acceptable. Inhalation of anesthetic gas or injection of parenteral general anesthetic agents are suitable for most species including pig, dog, cat, rodents, rabbits, birds and primates. Ether is extremely flammable and not acceptable. After anesthesia is induced by usual means, euthanasia may be completed by any of the following procedures:

• continued exposure to anesthetic for 5-30 minutes after breathing has stopped (newborn of most species are more resistant than adults to hypoxia and will require exposure times 2-3 times as long to assure death.);
• exsanguination;
• cervical dislocation (in small animals less than 200 gm);
• administration of injectable anesthetic or euthanasia preparation.
  

Physical Methods of Euthanasia

Cervical dislocation, dislocation of the neck, is a simple and humane method of killing mice and small rats (<125 gms). Although not required, the use of sedation or anesthesia prior to euthanasia is encouraged. If sedation or anesthesia prior to cervical dislocation is not used the investigator must provide scientific justification for its exclusion. In the case of mice and small rats, the animal is held by its tail and placed on a surface that it can grip, then it will stretch itself out so that a pencil or similar object can be placed firmly across the back of the neck. A sharp pull on the base of the tail will then dislocate the neck.

Decapitation is acceptable for rodents, rabbits and birds, and other animals of similar size. This requires special equipment and is aesthetically unacceptable to many. Although not required, the use of sedation or anesthesia prior to euthanasia is encouraged. If sedation or anesthesia prior to decapitation is not used the investigator must provide scientific justification for its exclusion.  In lieu of the use of anesthetics, prior recommendations have required the immediate placement of the decapitated head into liquid nitrogen. This is still an acceptable alternative however it is not required in part because of the human safety risk and is not recommended by the IACUC committee.

Barbiturates

Barbiturates such as pentobarbital or barbiturate combinations formulated for animal euthanasia are suitable for most species. Detailed records of use of these combinations must be maintained because they are controlled substances. Typically the dosage for euthanasia is three times the dose required for anesthesia. Table of barbiturate euthanizing doses.

Table of Euthanasia Methods:

• Rodents/Rabbits <125 gm
• Rodents/Rabbits > 125 gm and < 1 kg
• Rodents/Rabbits > 1 kg but < 5 kg
• Dogs and Cats
• Farm Animals
• Avian Species
• Nonhuman primates

Adapted from the report of the American Veterinary Medical Association Panel on Euthanasia (J. Am. Vet. Med. Assn. 218:669-695, 2001). The JAVMA article provides the rationale for these recommendations. The University Institutional Animal Care and Use Committee reviewed approved this table.

These methods are in accordance with humane euthanasia as defined by the Federal Animal Welfare Act (54 FR 36112-36163).

Methods always unacceptable in an awake animal include: potassium chloride, magnesium sulfate, strychnine, neuromuscular blocking agents, exsanguination, air embolism, and chloroform (due to its hazard to personnel).

Barbiturate euthanizing doses (mg/kg):

NOTE: Euthanasia with barbiturates usually requires approximately 3X the anesthetic dosage.