Euthanasia of Laboratory Animals

Recommendations from the AVMA Panel on Euthanasia

Amphibians Barbiturates, inhalant anesthetics (in appropriate Stunning and decapitation, decapitation and  
  species), CO2, tricaine methane sulfonate (TMS, pithing  
  MS 222), benzocaine hydrochloride, double    
Birds # Barbiturates, inhalant anesthetics, CO2 Cervical dislocation, decapitation  
Cats Barbiturates, inhalant anesthetics, potassium    
  chloride in conjunction with general anesthesia    
Dogs Barbiturates, inhalant anesthetics, potassium    
  chloride in conjunction with general anesthesia    
Fish Barbiturates, inhalant anesthetics, CO2, tricaine Decapitation and pithing, stunning and  
  methane sulfonate (TMS, MS 222), benzocaine decapitation/pithing  
  hydrochloride, 2-phenyoxyethanol    
Non-human primates Barbiturates Inhalant anesthetics  
Rabbits Barbiturates, inhalant anesthetics, potassium Cervical dislocation (<1 kg), decapitation  
  chloride in conjunction with general anesthesia    
Reptiles Barbiturates, inhalant anesthetics (in appropriate Decapitation and pithing, stunning and  
  species), CO2 (in appropriate species) decapitation and pithing  
Rodents Barbiturates, inhalant ansthetics, CO2, potassium Cervical dislocation (rats<200 g), decapitation  
  chloride in conjunction with general anesthesia    
Ruminants Barbiturates, potassium chloride in conjunction Chloral hydrate (IV, after sedation)  
  with general anesthesia    
Swine Barbiturates, CO2, potassium chloride in conjunction Inhalant anesthetics, chloral hydrate ( IV, after  
  with general anesthesia sedation  
* Acceptable methods are those that consistently produce a humane death when used as a sole means of euthanasia.  
** Conditionally acceptable methods are those that by the nature of the technique or because of the potential for  
operator error or safety hazards might not consistently produce humane death or are methods not well documented  
in the scientific literature.    
# Note: Large birds should receive general anesthesia before euthanasia    
Excerpted from the 2020 Report on the AVMA Panel on Euthanasia




Euthanizing Rodents Using the Euthanex™ CO2 System

The Euthanex™ CO2 system is provided in all DLAR facilities. The system decreases the amount of time required to euthanize mice and rats while providing the most humane CO2 euthanasia method possible for the animals.

Basic features of this system are:

  • Most animals are euthanized in their home cage which reduces the stress caused when animals from different cages are combined into a common container.
  • The stainless steel, gasketed lids fit directly on the top of the animals home cage.
  • A tube with a "quick release" connector attaches to a "port" on the top of the stainless steel lid - once one cage is filled with CO2, the "quick release" connector can be removed and attached to another cage.
  • The flow valve should be set for the appropriate cage size - mouse regular cage (1-3L/min) or mouse breeder cage or rat cage (10-12L/min)

CO2 chamber use

  • Place the animals in their home cage on the cart. Remove the microisolater bonnet, wire bar lid and water bottle.
  • Stainless steel lids are hanging on the wall holder, located near the CO2 tank. Place the appropriately sized lid directly on the top of the animals' cage.
  • Attach the clear plastic tube from the CO2 tank to the "port" on top of the stainless steel lid. Some tubes have metal connectors - pull "up" on the neck of the "quick release" connector to properly attach the tube.
  • Turn on the "turn valve" on top of the grey CO2 tank. Adjust the flow valve to the appropriate rate.
  • Fill in the cage with CO2 for 60-180 seconds, until all animals have stopped breathing.
  • Turn off the flow meter and the main "turn valve" on top of the tank and disconnect the plastic tube from the "port" on top of the lid.
  • Adult animals should remain in the cage with the stainless steel lid in place for approximately 5 minutes. Juveniles (10-21 days of age) should remain in the chamber for at least 15 minutes. Mice or rats less than 10 days of age should be decapitated with sharp scissors or a scalpel blade as they are insensitive to CO2. Confirm the death of each animal by checking for the presence of respiratory movement and a heartbeat. You may also create a pneumothorax, cervically dislocate or decapitate to ensure successful euthanasia.
  • Remove dead animals and place them in a plastic bag. The dead animals should be placed in the designated refrigerator located next to the CO2 system.
  • When all euthanasia is completed, please make sure the "turn valve" is completely closed.
  • When the tank pressure falls below 500 psi (i.e. in the "red zone"), please contact the vet staff (4-1161 or 4-6829).

If you are interested in donating euthanized animals to a local nature center, please contact Laurie at 444-2194.