Lethal injection

In the UK, killing by lethal injection can only be carried out by a veterinary surgeon. The animal will be injected intravenously with a lethal dose of anaesthetic drugs following, in some cases, initial injection of a sedative. The animal will rapidly lose consciousness and die. The most commonly used drugs for this are barbiturates in combination with other drugs. Animals should be restrained in order to guarantee effective administration. For some animals sedation may also be required to prevent movement during the injection. Intravenous administration is preferred, but intraperitoneal or intramuscular administration may be chosen. Doses and routes of administration which cause rapid loss of consciousness followed by death should be used. Animals should be monitored throughout the administration and the following period in order to ensure the drugs have been effectively administered and death can be confirmed by the absence of brainstem reflexes.

When an animal is killed by lethal injection there may be restrictions on how the carcase can be disposed of. The carcase cannot be used for human or animal consumption if it has been killed by lethal injection.

Considerations when using lethal injection during depopulation due to disease control

This method is appropriate during disease control operations, as the risks of infected body fluids entering the environment are minimal. Careful thought, however, must be given to the disposal of carcases when lethal injection has been used, as restrictions may be in place. The method is best suited to smaller animals but could potentially be used in all species across a variety of ages.

This method is advantageous from an animal welfare perspective as death is induced smoothly. As this method does not require bodily fluids to be expelled from the carcase, the biosecurity risk is minimised.

From a practical perspective there are a number of disadvantages to using this method during depopulation for disease control purposes. The application of restraint or sedation may cause distress to the animal, and close handling may prove to be a biosecurity risk when dealing with zoonotic diseases. There are also serious human safety risks if accidental injection to a person occurs. The availability and use of some drugs is restricted to veterinary surgeons and the administration requires specific skills and training. The time taken to perform this method means it is only suitable for use for a small number of animals. Some combinations of drug type or route of administration may be painful and should only be used in unconscious animals. Carcases which are contaminated with drugs present a risk to wild or domestic carrion feeders and, as such, there may be restrictions on carcase disposal.

Conclusion – species and situations

This method is most appropriate for use with small numbers of neonatal lambs, kids and piglets. Although potentially a high-welfare option, it is costly both in money and time. Its use may also be restricted due to the availability of particular drugs and skilled/licenced personnel.

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