BU IACUCInstitutional Animal Care and Use Committee IACUC oversee... Approved August 2008; Revised February 2012, Revised January 2014, Revised March 2019, Approved April 2019

Preferred methods of euthanasia are carbon dioxide asphyxiation for small adult rodents, and overdose of pentobarbital (intravenous) for larger species. Physical methods such as cervical dislocation of small rodents (less than 200g) and the use of a guillotine may be used but require training and approval by the IACUC. Proficiency for all users must be demonstrated.

Species-Specific Euthanasia

AnimalAcceptable Methods of Euthanasia
anesthetic overdose (e.g., immersion in 1% MS-222)
general anesthesia followed by vital tissue removal
carbon dioxide inhalationor
pentobarbital overdose (greater than 200mg/kg IP)
general anesthesia followed by vital tissue removal, perfusion, exanguination, or decapitation
PigNonhuman primate
pentobarbital overdose (greater than 120 mg/kg IV)
general anesthesia followed by vital tissue removal, perfusion, exsanguination, or decapitation


Pertains to adult animals. Neonatal mice, rats, hamsters, and gerbils are quite resistant to the effects of carbon dioxide. Anesthesia and IP injection are also difficult in neonates. Rodent pups less than seven days old may be made hypothermic prior to euthanasia by a physical method. The use of decapitation is permitted in neonatal mice, rats, hamsters, and gerbils due to their small size and incomplete neurologic development.

See additional information on appropriate use of CO2. This method of euthanasia may cause some postmortem artifacts, particularly in lung tissue. Consult veterinary staff for more information.

Other Methods of Euthanasia

The committee, on an individual basis, will review methods of euthanasia not listed in the above table. Evaluation of a proposed method of euthanasia will include assessment of:

  1. The proposed method’s ability to induce loss of consciousness and death without causing pain, distress, anxiety, or apprehension to the animal(s);
  2. The proposed method’s appropriateness for animal species and age;
  3. The proposed method’s reliability;
  4. The proposed method’s level of safety for personnel;
  5. The proposed method’s irreversibility;
  6. The proposed method’s likely emotional effect on human observers and/or operators; and
  7. The proposed method’s compatibility with research objectives.