Handling and restraint for euthanasia

Some methods of euthanasia (e.g. use of overdose of an inhalational anaesthetic or use of carbon dioxide) can be carried out without handling the animal if all the animals in the cage are to be killed at the same time. This reduces to a minimum the stress associated with handling, but moving the cage from the animal room to the area in which the animals are to be killed must be done carefully, avoiding unnecessary disturbance to the animals. Whenever possible, euthanise the animals immediately after moving them.

When killing individual animals in a group, or when using a method that requires handling and restraint, it is important that this is done in a careful and competent way. Almost all laboratory animals can be restrained safely and humanely provided they are handled correctly. Different methods of restraint can influence the degree of stress experienced by the animal; for example, it has been shown that picking up mice by the tail induces aversion and high levels of anxiety (Hurst and West, 2010¹, Gouveia and Hurst, 2017²). Using tunnels or cupping the mice in open hands leads to more rapid acceptance of physical restraint. Habituation to this type of initial restraint persists even when mice are subsequently restrained more securely, for example by the scruff to allow intraperitoneal injection of anaesthetic, to be carried out.

Restraint will be stressful, even in animals that have become accustomed to handling during the course of a research project, so the duration of restraint should be minimised. If you are relatively inexperienced in the technique that you plan to use for euthanasia, you should ensure you have an experienced assistant who can restrain the animal safely and humanely, and assist and supervise the procedure. When carrying out procedures, make sure you are wearing appropriate protective clothing, to protect yourself from hazards such as allergens.

Methods for handling and restraint of rodents suitable for moving them from their home cage into a chamber for euthanasia, or restraining them for the administration of an overdose of anaesthetic by intraperitoneal injection or intravenous injection are shown here www.procedureswithcare.org.uk .

1. Hurst, J.L. and West, R.S., 2010. Taming anxiety in laboratory mice. Nature methods, 7(10), p.825.
2. Gouveia, K. and Hurst, J.L., 2017. Optimising reliability of mouse performance in behavioural testing: the major role of non-aversive handling. Scientific Reports, 7, p.44999.