Some accept

Agent

Classification

Mode of action

Rapidity†

Ease of performance Safety for personnel Species suitability

Efficacy and comments

Conditions

Inhalant anesthetics Hypoxia attributable to depression of vital centers Direct depression of cerebral cortex, subcortical structures, and vital centers Moderately rapid onset of anesthesia, excitation may develop during induction Easily performed with closed container (including topical or immersion as appropriate by species); can be administered to large animals by means of a mask Effective procedures should be in place to reduce animal worker exposure to anesthetic vapors Most animals excluding livestock, finfish, and many amphibians and reptiles Highly effective provided that subject is sufficiently exposed

Maceration

Physical damage to brain Direct concussion of brain tissue

Immediate

Easily performed with properly designed, commercially available equipment and trained personnel Generally safe; macerated tissues may present biosecurity risks Newly hatched chicks and poults, and pipped eggs only

Effective

Specialized equipment in excellent working order must be used

Focused beam microwave irradiation Brain enzyme inactivation Direct inactivation of brain enzymes by rapid heating of brain

Very rapid

Requires training and highly specialized equipment

Safe

Mice and rats

Highly effective for special needs Only instruments that are designed for this use and have appropriate power and microwave distribution can be used

Nitrogen, argon

Hypoxia

Reduces partial pressure of oxygen available to blood

Rapid

Used in closed chamber with rapid filling Safe if used with ventilation Chickens, turkeys, and swine Effective except in young and neonates; an effective agent, but other methods are preferable in species where aversion is noted These gases must be supplied in a precisely regulated and purified form without contaminants or adulterants; an appropriate pressure-reducing regulator and flow meter combination or equivalent equipment must be used

Potassium chloride

Cardiotoxic

Direct depression of cerebral cortex, subcortical structures, and vital centers secondary to cardiac arrest

Rapid

Requires training and ability to give IV injection of potassium chloride Anesthetics may be hazardous with accidental human exposure

Most species

Highly effective, some clonic muscle spasms may be observed Intracardially or IV with an animal that is unconscious or under general anesthesia only; unacceptable when used in conscious vertebrate animals

Penetrating captive bolt Physical damage to brain Direct concussion of brain tissue

Immediate

Requires skill, adequate restraint, and proper placement of captive bolt; can be aesthetically displeasing

Safe

Horses, ruminants, swine and nondomestic species, as appropriate Instant loss of consciousness, but motor activity may continue Animals be immediately exsanguinated or pithed unless a powerful captive bolt gun designed for euthanasia is used; captive bolt guns used for larger species must have an extended bolt

Tricaine methane sulfonate (TMS, MS 222) Hypoxia attributable to decreased nervous and cardiovascular function

Depression of CNS

Rapid, depending on dose

Easily used

Associated with retinal toxicity in humans Finfish, some reptiles, amphibians, and cold-blooded aquatics

Effective but expensive

The solution should be buffered with sodium bicarbonate; a secondary method of euthanasia is recommended in some finfish and amphibians

2-phenoxyethanol

Hypoxia attributable to depression of vital centers

Depression of CNS

Rapid, depending on dose

Easily used

Safe

Finfish

There are probably more efficient immersion agents available There are species variations in dosage levels and duration of exposure required for euthanasia. Finfish should be kept in the 2-phenoxyethanol solution for at least 10 minutes after cessation of opercular movement

*Acceptable, acceptable with conditions, and adjunctive methods have been included in this appendix, with the appropriate qualifications. †Immediate = Upon application. V

ery rapid = T

ypically within seconds. Rapid = T

ypically within a few minutes.

DEA = Drug Enforcement Agency

.

Appendix 2 (continued) Some accept

Agent or method Comments

Air embolism Air embolism may be accompanied by convulsions, opisthotonos, and vocalization. If used, it should be done only in anesthetized animals.

Burning Chemical or thermal burning of an animal is not an acceptable method of euthanasia. Chloral hydrate Unacceptable.

Chloroform Chloroform is a known hepatotoxin and suspected carcinogen and, therefore, is extremely hazardous to personnel.

Cyanide Cyanide poses an extreme danger to personnel and the manner of death is aesthetically objectionable.

Decompression (excluding low- atmospheric-pressure stunning when it can be demonstrated that it achieves euthanasia)

Decompression is unacceptable for euthanasia because of numerous disadvantages. (1) Many chambers are designed to produce decompression at a rate 15–60 times as fast as the recommended optimum for animals, resulting in pain and distress attributable to expanding gases trapped in body cavities. (2) Immature animals are tolerant of hypoxia, and longer periods of decompression are required before respiration ceases. (3) Accidental recompression, with recovery of injured animals, can occur. (4) Bleeding, vomiting, convulsions, urination, and defecation, which are aesthetically unpleasant, may develop in unconscious animals. Diethyl ether Diethyl ether is irritating, flammable, and explosive. Explosions have occurred when animals,

euthanatized with ether, were placed in a non-explosion-proof refrigerator or freezer and when bagged animals were placed in an incinerator.

Drowning Drowning is not a means of euthanasia and is inhumane.

Exsanguination Because of the anxiety associated with extreme hypovolemia, exsanguination as a sole method of killing should be used only on unconscious animals.

Formaldehyde Direct immersion of an animal into formalin, as a means of euthanasia, is inhumane with the exception of Porifera.

Household products and solvents Acetone, cleaning agents, quaternary compounds (including CCl4), laxatives, pesticides, dimethylketone, quaternary ammonium products, antacids, and other toxicants not specifically designed for therapeutic or euthanasia use are not acceptable.

Hypothermia Hypothermia is not an appropriate method of euthanasia. Magnesium sulfate, potassium chloride,

and neuromuscular blocking agents Unacceptable for use as euthanasia agents in conscious vertebrate animals. Manually applied blunt force trauma to

the head Generally unacceptable for most species excluding piglets and small laboratory animals. Replace, as much as possible, manually applied blunt force trauma to the head with alternate methods.

Nonpenetrating captive bolt Unacceptable excluding purpose-built pneumatic nonpenetrating captive bolt guns used on suckling pigs, neonatal ruminants, and turkeys.

Neuromuscular blocking agents (nicotine, magnesium sulfate, potassium chloride, and all curariform agents)

When used alone, these drugs all cause respiratory arrest before loss of consciousness, so the animal may perceive pain and distress after it is immobilized.

Rapid freezing Rapid freezing as a sole means of euthanasia is not considered to be humane with the exception of reptiles and amphibians and < 5-day-old altricial rodents. In all other cases animals should be rendered dead or unconscious prior to freezing. (Rapid chilling of finfish is not considered to be rapid freezing.)

Smothering Smothering of chicks or poults in bags or containers is not acceptable. Strychnine Strychnine causes violent convulsions and painful muscle contractions. Thoracic compression Not acceptable for use on a conscious animal.

Appendix 3