Euthanasia is performed on millions of laboratory animals annually. Choosing the most humane methods and implementing them correctly is a fundamental welfare responsibility in research settings.
Laboratory animal euthanasia is a welfare obligation requiring species-appropriate methods implemented by competent, trained personnel. Carbon dioxide — despite being the dominant method for rodent euthanasia globally — is now recognised to cause aversion before unconsciousness, with animals showing escape behaviour and stress responses during the pre-unconsciousness phase. Alternatives including inhalant anaesthetics before CO2 application, or alternative euthanasia agents, produce less aversive experiences. Physical methods when used must be carried out by trained personnel to be instantaneous and humane. Euthanasia welfare extends beyond the act itself: housing animals in conditions of chronic stress before euthanasia, or performing euthanasia in ways that cause fear through unusual environments or conspecific alarm responses, compounds welfare harms. Training, oversight, and regular review of euthanasia methods are fundamental welfare management responsibilities.