TABLE 7-1 General Recommendations for Euthanasia (Categorized by Agent)

Agent or Method

Suitable Species


Carbon dioxide

Small laboratory animals, small dogs and puppies, cats and kittens, birds, small swine, and terrestrial reptiles and amphibians

Not recommended for newborn animals


Most species

Agent of choice

Methoxyflurane and halothane

Most laboratory animals



Small laboratory animals, snakes, lizards, turtles, terrapins, tortoises, frogs, toads, newts, salamanders, and fish

Follow by immediate killing

Cervical dislocation

Small laboratory animals



Rodents and birds

Aesthetically unpleasant and dangerous for operator

Captive bolt

Large farm animals

Follow by immediate killing


Large animals and crocodilians

Useful in field studies, on farms, and in emergencies

Microwave irradiation

Mice and rats

Requires focused-beam instrument; expensive

Tricaine methanesulfate

Frogs, toads, newts, salamanders, and fish



A number of inhalational agents have been used for euthanasia, including ether, chloroform, halothane, methoxyflurane, enflurane, isoflurane, cyclopropane, nitrous oxide, and the nonanesthetic gases carbon monoxide (CO), carbon dioxide (CO2), nitrogen, argon, and hydrogen cyanide. Inhalational agents are usually administered in closed containers or chambers and have been used for small animals, such as rodents, rabbits, birds, puppies, kittens, and cats. Adequate ventilation and a means of exhausting waste gases should be provided for the safety of attendants using these agents.

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