The method of euthanasia in laboratories is a critical welfare decision affecting millions of animals annually and standards vary significantly across institutions and species.
Euthanasia method selection is a welfare decision that directly affects the final experience of millions of laboratory animals. Carbon dioxide, despite widespread use, causes measurable distress in rodents during the induction phase. Alternatives including pentobarbital injection or isoflurane pre-exposure before CO2 introduction significantly reduce or eliminate distress but require more resources. Fish euthanasia is frequently inadequate because methods validated for mammals are applied inappropriately. Institutional variation in euthanasia standards means the same species may receive markedly different welfare at its death depending on where it is used. Evidence-based protocols applied consistently represent a straightforward welfare improvement.