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Rodents

Euthanasia Methods

CO2

Acceptable with conditions for euthanasia of small laboratory rodents.

  • Death must be verified after euthanasia and prior to disposal. Death may be ensured by cervical dislocation, decapitation or opening of the chest cavity after CO2 euthanasia.
  • All individuals administering CO2 euthanasia must be appropriately trained and monitored. IACUC-approved protocols and institutional policies regarding CO2 euthanasia must be followed.
  • If euthanasia can not be carried out in the animal's home cage, euthanasia chambers must not be overcrowded and should be cleaned between uses. Unfamiliar or incompatible animals should not be placed into the same chamber or cage as this will be distressful.
  • Compressed CO2 in cylinders is the only AVMA Panel-recommended source of CO2 for euthanasia purposes.
  • Gas inflow into the euthanasia chamber must be regulated to displace 10-30% of the chamber or cage volume per minute. Do not prefill the chamber.

 

Recommendation:

  • At Penn State, CO2 is the preferred method of euthanasia for rodents. CO2 tanks with euthanasia chambers are located in many of the procedure rooms as well as in the necropsy room. Dry ice may not be used to generate CO2 for euthanasia.
  • Gas flow should be maintained for at least one minute after apparent clinical death (cessation of respiration). If an animal is not dead, CO2 narcosis must be followed with another method of euthanasia.
  • To insure that unintended recovery does not occur after CO2 exposure, cervical dislocation or decapitation may be performed or a puncture incision may be made (between the ribs) into the chest cavity on both sides of the animal.

Neonatal rodents are resistant to CO2 induced euthanasia. Euthanasia of neonatal rodents is discussed below.

Volatile Inhalant Anesthetics

Acceptable with conditions for euthanasia of laboratory rodents.

  • Although inhalant anesthetics may be useful in instances where physical restraint is difficult, euthanasia via inhalant anesthesia may require prolonged exposure to achieve death.
  • Animals are placed in a sealed container such as a bell jar containing gauze soaked with the anesthetic agent.
  • Animals should be separated from the anesthetic soaked gauze by a false bottom or other method to prevent direct animal contact with the liquid anesthetic.
  • A number of volatile inhalant anesthetics may be used for anesthesia. Contact an ARP veterinarian for information regarding the use of volatile inhalant anesthetics for euthanasia.
  • All volatile inhalant anesthetics require some method of scavenging the waste anesthetic vapors (i.e., working in a biosafety cabinet).

Cervical Dislocation

Acceptable with conditions for euthanasia of mice and rats weighing <200 grams.

  • Personnel should be trained on anesthetized or dead animals to demonstrate proficiency.
  • Investigators are responsible to determine that personnel using cervical dislocation are properly trained to do so. ARP will provide training to those who request it.

Decapitation

Acceptable with conditions for euthanasia of mice and rats.

  • Personnel should be trained on anesthetized or dead animals to demonstrate proficiency.
  • Rodent guillotines must be kept clean and in good condition with sharp blades.
  • Investigators are responsible to determine that personnel using decapition are properly trained to do so. ARP will provide training to those who request it.

Barbiturates and Dissociative agent combinations

Acceptable methods for the euthanasia of laboratory rodents.

  • May be injected intraperitoneally.
  • Agents available for use include pentobarbital or ketamine combined with xylazine or diazepam.
  • Barbiturate drugs must be used under the supervision of personnel registered with the United States Drug Enforcement Administration (DEA).

Neonatal Rodents

  • Young altricial rodents such as mice and rats must be treated differently from adults of these species when euthanized.
  • Mammalian fetuses are unconscious in utero. It is not necessary to remove rodent fetuses for euthanasia after the dam is euthanized.
  • Neonatal rodents up to 10 days of age are resistant to euthanasia with CO2. Neonatal mice have been shown to take up to 50 minutes to die from CO2 exposure alone.
  • Although neonates are resistant to CO2, prolonged exposure will induce anesthesia. Exposure to CO2 or a volatile anesthetic (until nonresponsive) should be followed with an adjunctive method of euthanasia such as decapitation or cervical dislocation.