IACUC Policy for Euthanasia of Research Animals
- Definition
- Policy
- Insuring Euthanasia of Laboratory Animals
- Euthanasia Criteria
- Additional Recommended Practices to Insure Death in Rodents
- Who to Contact for Help
Definition
Euthanasia is the act of inducing humane death in an animal by a method that induces rapid loss of consciousness and death with a minimum of pain, discomfort or distress.
Policy
Animal welfare regulations require that the Institutional Animal Care and Use Committee (IACUC) approve the euthanasia method for research animals. The proposed method of euthanasia and the criteria that will be used to assess pain and distress in animals that need to be euthanized ahead of schedule must be described in detail in the IACUC Application to Use Animals in Research or Teaching. Additionally, a plan for responding to calls from by Veterinary Services about sick or injured animals must be described.
It is the responsibility of the Lead Researcher to assure that each member of the study team is prepared and familiar with an established course of action in the event that an animal requires euthanasia to alleviate pain, distress or discomfort. At least one member of the study team must be available locally at all times to euthanize any animal exhibiting symptoms consistent with pain, distress and/or discomfort. Lead Researchers are primarily responsible for the euthanasia of all animals purchased or bred under their approved protocols. ULAR staff will only euthanize animals after contacting laboratory staff, unless immediate euthanasia is required to relieve acute animal suffering.
Insuring Euthanasia of Laboratory Animals
Most experimental animal use protocols involve the euthanasia of study animals at some predetermined end point. The table below summarizes the American Veterinary Medical Association's (AVMA) recommendations on humane euthanasia methods. Successful application of the methods outlined above requires that personnel are adequately trained in performing the various techniques and that personnel are competent in confirming that death has occurred.
A profoundly anesthetized or severely ill animal can easily appear dead upon cursory examination; one can not rely solely on imprecise measures such as lack of movement and lack of visible breathing to declare an animal dead. Personnel who are trained to recognize cessation of vital signs in the species being euthanized must confirm the death of an animal. In addition, multiple assessment parameters should be employed. Rodents, especially neonates, are particularly resistant to euthanasia by overdose of inhaled agents such as CO2; for this reason, the IACUC requires that a secondary physical method of euthanasia (e.g. cervical dislocation or decapitation) be performed after the animal is profoundly anesthetized, prior to carcass disposal.
NOTE: Unintended recovery of animals after apparent death from CO2 or other inhalant euthanasia constitutes serious noncompliance with the PHS Policy and unacceptable deviation from the provisions of the Guide for the Care and Use of Laboratory Animals.
Euthanasia Criteria
Most experimental animal use protocols involve the euthanasia of study animals at a predetermined end point when the animals are clinically healthy. However, in the event animals become ill or debilitated, either as a result of spontaneous disease or as a result of research, the criteria below must be utilized in the decision to provide euthanasia. Fulfillment of one criterion can constitute grounds for euthanasia. Exceptions are permitted only if approved by the IACUC as part of the protocol review process (i.e.: the clinical signs listed below are expected as part of the experiment and appropriate measures are taken to minimize pain or discomfort in the animals).
Animals experiencing one or more of the criteria listed below must be euthanized. If veterinary personnel identify such animals, an attempt will be made to contact the primary investigator or an alternate responsible person. If a responsible person can not be located, a ULAR veterinarian will authorize euthanasia of severely debilitated or moribund animal.
- Weight loss: loss of >20 percent of body weight (depending on attitude, weight recorded at time of arrival, and age: growing animals may not lose weight, but may not gain normally); or if not measured, characterized by cachexia and muscle wasting.
- Change in appetite: complete anorexia for 24 hours in small rodents, up to 5 days in large animals; partial anorexia (less than 50% of caloric requirement) for 3 days in rodents, 7 days in large animals.
- Weakness/inability to obtain feed or water: Inability or extreme reluctance to stand which persists for 24 hours (assuming that the animal has recovered from anesthesia).
- Moribund state: depression, complete anorexia and hypothermia with little likelihood to recover (assuming that the animal has fully recovered from anesthesia).
- Infection: infection involving any organ system (either overt, or indicated by increased body temperature or WBC parameters) which fails to respond to antibiotic therapy within an appropriate time, and is accompanied by systemic signs of illness.
- Organ dysfunction/failure: signs of severe organ system dysfunction non- responsive to treatment, or with a poor prognosis as determined by a ULAR veterinarian:
- Respiratory: dyspnea and cyanosis unresponsive to appropriate medical therapy.
- Cardiovascular: acute blood loss resulting in hematocrit below 20% or severe chronic anemia (Hct < 15%).
- Gastrointestinal: severe vomiting or diarrhea (duration greater than 24 hours, unresponsive to medical therapy), obstruction, intussusception.
- Urogenital: renal failure characterized by elevated BUN, creatinine or uroperitoneum.
- Nervous: CNS depression, seizures, paralysis of one or more extremities; pain unresponsive to analgesic therapy.
- Musculoskeletal: muscle damage or fracture resulting in inability to use the limb, unless anticipated as part of the study.
- Integumentary: Non-healing wounds, repeated self-trauma, second or third degree heating pad burns.
- Tumor growth: Solid tumors that exceed 10 percent of normal body weight in rodents (i.e.: 1 cm3 = 1 gm); or tumor growth that impedes an animal's ability to ingest food, water or ability to move about its cage and remain clean and dry.
- Uncontrollable pain/distress: animals showing signs of pain and/or distress that is not responsive to analgesics/anesthetics, or as determined by a ULAR veterinarian.
| Species | Acceptable2 | Conditionally Acceptable3 | Notes |
|---|---|---|---|
| Amphibians |
Barbiturates Inhalant anesthetics Tricaine methane sulfonate (TMS, MS222) † Benzocaine HCL (via immersion) Double pithing |
Penetrating captive bolt Gunshot Stunning and decapitation Decapitation and pithing |
† MS 222 solution.: concentration >250 mg/l,
buffered (pH 7-7.5); can be administered by immersion or injection into
dorsal lymph sacs and pleuroperitoneal cavity
* see below |
| Avian |
Barbiturates Inhalant anesthetics CO, CO2* Gunshot (free-ranging only) |
N2, Ar Cervical dislocation Decapitation Thoracic compression † |
† Small to medium sized free ranging birds only; only applicable in field conditions when no other method is feasible. |
| Cats |
Barbiturates Inhalant anesthetics CO, CO2* KCl (in conjunction with anesthesia) |
N2, Ar | * see below |
| Dogs |
Barbiturates Inhalant anesthetics CO, CO2* KCl (in conjunction with anesthesia) |
N2, Ar Penetrating captive bolt Electrocution |
* see below |
| Fish |
Barbiturates Inhalant anesthetics CO2* Tricaine methane sulfonate (TMS, MS222) † Benzocaine HCL (via immersion) 2-phenoxyethanol |
Decapitation and pithing Stunning and decapitation/pithing |
† MS 222 solution.: concentration >250 mg/l, buffered (pH 7-7.5); can be administered by immersion or injection into dorsal lymph sacs and pleuroperitoneal cavity |
| Nonhuman Primates | Barbiturates |
Inhalant anesthetics CO, CO2, N2, Ar |
|
| Rabbits |
Barbiturates Inhalant anesthetics CO, CO2* KCl (in conjunction with anesthesia) |
N2, Ar Cervical dislocation (<1 kg) Decapitation Penetrating captive bolt |
* see below |
| Reptiles |
Barbiturates Inhalant anesthetics |
Penetrating captive bolt Gunshot Decapitation and pithing Stunning and decapitation |
* see below |
|
Rodents (& other small mammals) |
Barbiturates Inhalant anesthetics CO, CO2* KCl (in conjunction with anesthesia) Microwave irradiation † |
Methoxyflurane Ether N2, Ar Cervical dislocation (rats < 200g) Decapitation |
† Only microwaves
specifically designed for euthanasia of mice and rats may be used; high
energy 1.3-10 kw. *see below |
| Ruminants |
Barbiturates KCl (in conjunction with anesthesia) Penetrating captive bolt |
Chloral hydrate (IV, after
sedation) Gunshot Electrocution † |
† Animals must be unconscious prior to electrocution. |
| Swine |
Barbiturates CO2* KCl (in conjunction with anesthesia) Penetrating captive bolt |
Inhalant anesthetics CO Chloral hydrate (IV, after sedation) Gunshot Electrocution † Blow to the head (< 3 weeks of age) |
† Animals must be
unconscious prior to electrocution. * see below |
| Free-ranging wildlife |
Barbiturates IV or IP Inhalant anesthetics KCl (in conjunction with anesthesia) |
CO2*, CO, N2,
Ar Penetrating captive bolt Gunshot Kill traps (scientifically tested) |
* see below |
* The following additional guidelines should be followed when using CO2 as a euthanasia agent:
- Neonatal rodents are often not affected by the concentrations of CO2 which will kill an adult rodent. Therefore extra CO2 exposure time (10-30 minutes) should be allowed and/or added measures taken to confirm death in neonates.
- CO2 must be delivered from compressed gas canister only, i.e.: not from dry ice.
- High concentrations of CO2 may be distressful to some species. Accordingly, pre-filling the chamber is recommended only under circumstances in which such use has not been shown to cause distress.
Notes and References:
- JAVMA, Vol 218, No. 5, March 1, 2001 2000 Report of the AVMA Panel on Euthanasia (PDF)
- All euthanasia methods must be described in an approved IACUC protocol.
- Conditionally acceptable euthanasia methods may only be performed when scientifically justified and approved by the IACUC.
Assessment Parameters for Confirmation of Death
- Heart beat: must be assessed for a minute or more. The best assessment is through direct palpation of either the pulse in the carotid or femoral artery of a large animal or direct cardiac palpation. If there is any question, the thorax should be opened, the heart exposed, viewed directly and its mechanical activity observed and palpated. Arterial pulse of smaller species such as mice and rats is difficult to palpate, so direct inspection of cardiac mechanical activity is necessary. Lack of electrical activity of the heart as determined by ECG (provided that the leads are correctly connected) may also be utilized to document euthanasia.
- Pupillary response to light: Shine a bright light into the eyes of the animal. A constriction (narrowing) of the pupil indicates a neurological response. Upon death, the pupils will become dilated and fail to constrict in response to light. Investigators should be aware that some drugs and experimental agents (e.g., anticholinergics such as atropine) can prevent pupillary reactivity or otherwise affect this neurological response.
- Respiratory pattern: Profoundly anesthetized animals may exhibit shallow and irregular breathing patterns that may be confused for lack of spontaneous breathing. Thus, lack of spontaneous breathing should not be used as sole criteria for confirming euthanasia.
Additional Recommended Practices to Insure Death in Rodents
The criteria listed above (assessment of heart beat, papillary light response and respiratory pattern) may be difficult to apply to rodents due to their small size; consequently, there is a risk of animals recovering after they are presumed dead, particularly following the use of inhalant agents. The following additional steps must be taken to insure that animals are properly euthanized.
- Animals must be rechecked for lack of vital signs 5-10 minutes after the administration of the euthanasia agent (e.g., C02, anesthetic overdose).
- A physical method of euthanasia after an animal is rendered unconscious and insensitive to pain. Examples include:
- Exsanguination – i.e., great vessels severed, cardiac perfusion, removal of vital organs.
- Incision of the chest cavity to produce a pneumothorax (collapsed lung) and cessation of respiration.
- Decapitation or cervical dislocation.
Who to Contact for Help:
For more detailed information and training in acceptable euthanasia methods, please contact Veterinary Services at 824-9616.
