Rodent Euthanasia  | Neonatal Rodent Euthanasia  | Rabbit Euthanasia  | Amphibian, Fish & Reptile Euthanasia | Compassion Fatigue



Euthanasia is the act of killing animals using methods that cause minimal animal pain, distress and anxiety prior to rapid loss of consciousness and death. Only trained personnel may perform euthanasia. The principal investigator is responsible for ensuring that personnel performing euthanasia have been trained to perform the procedure used. Training in euthanasia procedures is available from ARP veterinarians, veterinary technicians and animal caretakers. Unless approved by the IACUC, euthanasia may only be performed using methods listed as acceptable by the AVMA Guidelines on Euthanasia.

Carcasses should be placed in a plastic bag (available in each facility), labeled, and put in the appropriate animal facility refrigerator or freezer. These animals will be picked up for incineration. Do not place dead animals or animal tissues in a waste receptacle or dumpster.

Selected agents and methods of euthanasia by species

The American Veterinary Medical Association has published Guidelines on Euthanasia for many species, including most laboratory species. Research personnel are expected to use and follow the AVMA Guidelines. These guidelines specify the criteria used to determine the methods of euthanasia that may be used in each species. Euthanasia methods are categorized into acceptable, acceptable with conditions and unacceptable. Investigators who wish to include euthanasia methods listed as acceptable with conditions in their protocol must provide scientific justification and receive IACUC approval prior to use.

  • Acceptable - those methods that reliably meet the requirements of euthanasia.
  • Acceptable with conditions -Methods that reliably meet the requirements of euthanasia when specified conditions are met. Please consult the AVMA Guidelines for specific information.
  • Unacceptable - those methods deemed inhumane under any conditions or do not meet the requirements for euthanasia.
  • Adjunctive method -A method of assuring death that may be used after an animal has been made unconscious.


Species Acceptable (see AVMA Guidelines for further information and specifications) Acceptable with conditions (see AVMA Guidelines for further information and specifications)
Amphibians As appropriate by species: Injectable barbiturates, dissociative agents and anesthetics, topical buffered MS222, benzocaine hydrochloride As appropriate by species: Inhaled anesthetics (see specifications), CO2,blunt force trauma to head, rapid freezing.
Birds Intravenous barbiturates Inhaled anesthetics, CO2, cervical dislocation (small birds and poultry), decapitation (small birds), gunshot (free ranging birds)
Deer Intravenous barbiturates (with prior sedation) Gun shot (must demonstrate proficiency)
Fish Immersion in buffered benzocaine or benzocaine hydrochloride, isoflurane, buffered MS222, 2-phenoxyethanol, injected pentobarbital, rapid chilling (research zebrafish) Eugenol, isoeugenol, clove oil, decapitation/cervical transection/blunt force trauma followed by pithing
Horses Barbiturates  
Rabbits Intravenous barbiturates Inhaled anesthetic overdose, cervical dislocation (< 1kg), penetrating captive bolt
Reptiles As appropriate by species: Injected barbiturates, dissociative agents and anesthetics as specified As appropriate by species: Inhaled anesthetics as specified, CO2, blunt force trauma to head, rapid freezing for animals < 4 g
Rodents Injected barbiturates and dissociative agent combinations Inhaled anesthetics, CO2, tribromoethanol, cervical dislocation, decapitation
Ruminants Intravenous barbiturates Penetrating captive bolt
Swine-Suckling pigs < 12 lbs Intravenous barbiturates CO2, blow to the head (< 3 weeks of age)
Swine- Nursery pigs < 70 lbs Intravenous barbiturates CO2, Nonpenetrating captive bolt
Swine- Grow/Finish to Mature pigs Intravenous barbiturates Penetrating captive bolt, gunshot
Free ranging wildlife Two stage method of euthanasia is preferred: General anesthesia or deep sedation followed by barbiturate overdose. CO2, gunshot

Please consult with an ARP veterinarian for further information or for information on euthanasia in specific species.

Rodent Euthanasia Methods


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.
  • CO2 tanks with euthanasia chambers are located in many of the animal facility procedure rooms. Dry ice must not be used to generate CO2 for euthanasia.
  • Gas inflow into the euthanasia chamber must be regulated to displace 30-70% of the chamber or cage volume per minute. Do not prefill the chamber.

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.



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.
  • Many of these drugs are regulated by the DEA (Drug Enforcement Administration) because of the potential for abuse.  Investigators using them are responsible for complying with applicable regulations for licensing and use. 


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. Published studies have shown that neonatal rodents may survive for up to 50 minutes during CO2 exposure.
  • Although neonates are resistant to CO2, prolonged exposure will induce anesthesia. Following exposure to CO2 or a volatile anesthetic (until nonresponsive) death must be verified using an adjunctive method of euthanasia such as decapitation. 


Rabbit Euthanasia Methods


  • Acceptable when administered intravenously
  • Barbiturates injected intravenously induce rapid euthanasia.
  • Barbiturates may also be administered to unconscious animals by intracardiac injection.
  • Sodium pentobarbital and several pentobarbital combination drugs may be used for euthanasia.
  • Barbiturate drugs used for anesthesia, analgesia, and euthanasia are regulated by the DEA (Drug Enforcement Administration) because of the potential for abuse.  Investigators using these drugs are responsible for complying with applicable regulations for licensing and use. 
  • Sodium pentobarbital is a (DEA) Schedule II drug and therefore more difficult to obtain than the pentobarbital combinations marketed for euthanasia that are Schedule III drugs.
  • Federal requirements for record keeping and locked storage must be followed.



  • May only be used as an adjunctive method to euthanize unconscious animals.


Amphibian, Fish & Reptile Euthanasia Methods

Many methods of euthanasia are available for amphibian, fish and reptile species. Due to significant variations in species anatomy, physiology and sensitivity to drugs, a particular euthanasia method may be acceptable for some species but not others. Investigators are encouraged to consult appropriate regulatory and scientific literature and make an educated decision as to which method(s) will provide the most humane euthanasia for the species they are using.

The following references are available online and provide extensive information on euthanasia in amphibians, fish and reptiles:


The information presented in this website is intended as a resource for Pennsylvania State University research investigators. No guarantee of efficacy or safety is made nor must information obtained from this site be substituted for professional veterinary advice.

Compassion Fatigue

Some research personnel may experience difficult emotions and moral stress when performing euthanasia as part of their duties. The term compassion fatigue is used to describe the manifestation of stress that presents as physical, emotional, and psychological exhaustion associated with caring for research animals. Although compassion fatigue is a normal consequence of caring, it can adversely impact quality of life if not managed. To learn more about compassion fatigue, read the Cost of Caring brochure provided by the American Association for Laboratory Animal Science.

If you are struggling with compassion fatigue, the Pennsylvania State University provides counseling and mental health services to all faculty, staff, and students: