Destination animals

Most animals are killed after an animal experiment because further research of animal tissue is part of the experiment. But animals can also be reused. This happens in education, for example, when animals are used repeatedly in a practical where students learn how to handle or treat an animal. Animals can also be offered to other researchers, so that the purchase of new animals can be prevented.


The work protocol describes whether the animal is killed at the end of the experiment or is presented as “surplus”. Surplus laboratory animals can be laboratory animals that have been used for an animal experimental study or education and where killing the animals after the research is not necessary. It may also concern animals from breeding activities. For example, breeding parents that need to be replaced over time, offspring that do not have the correct sex or genetic background or that are supernumerary for other reasons. It may also concern animals that were ordered but ultimately not used, for example because the planned trial could unexpectedly be canceled.

The researcher must inform the IvD of available surplus animals, so that the IvD can share the necessary information with the laboratory animal coordinators. If interested in reuse, the IvD assesses whether the animals may be used for the stated purpose.


Re-use is when one test uses animals that have previously been used in another test. The use of surplus laboratory animals for research, education and training is encouraged because this can contribute to reducing the number of laboratory animals required. If animals are reused, no other animals need to be purchased or bred. There are of course certain conditions that an animal must meet:

• the actual degree of discomfort in the previous test was "mild" or "moderate"; and
• the animal's general health and welfare status has been fully restored after the previous experiment; and
• the expected discomfort from the following animal experiment has been estimated as "mild", "moderate" or "terminal"
• the actions to be performed are in accordance with veterinary advice.

Rehoming or euthanasia

Sometimes a laboratory animal cannot be (re)used because of disease, old age, behavior, or because researchers are not interested in that type of animal. In those cases we try to relocate the animal outside the institution (adoption). If the animal is not suitable for reassignment, for example due to a disease present, a genetic modification, the presence of an infectious agent or abnormal behavior, then euthanasia or, in the case of farm animals, slaughter is chosen. Even if no new owner can be found within a predetermined period, euthanasia or slaughter is chosen.

The assessment of whether a choice is made for rehoming or euthanasia is done in mutual consultation between the laboratory animal coordinator, the daily caretaker of the laboratory animal, the Animal Welfare Body (IvD) Utrecht and the responsible researcher or other relevant officials within the chain.

More information about looking for new owners can be found at adoption.

Tissue for more purposes

If an animal is killed as part of an animal experiment, the entire animal is not always necessary. It may happen that only the heart or another organ is needed from the test animal. The remaining fabrics can then be used for other research or teaching purposes. If additional actions are required on the living animal, permission from the IvD is required.

There are research groups that notify each other when an animal is euthanized as part of an experiment, where not all tissues are needed. This works well internally and contributes to reducing the number of laboratory animals required.

In order to further facilitate the exchange and thus a more optimal use of tissues and animals, a digital exchange platform is currently being developed, where researchers can exchange surplus animals and (vital) tissue.