Jaarverslag 2018



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Utrecht University and University Medical Center Utrecht 2018

Annual Report on Animal Experiments

English summary

This 2018 the English summary of the Annual Report on Animal Experiments by Utrecht University and the University Medical Center Utrecht (UMC Utrecht). It provides information about the use of laboratory animals by the two institutions.

This publication was prompted in part by the Dutch Code for Transparency in Animal Testing (Dutch only). It is one of the many tools we use for being transparent about experiments on animals. For example, there are the very informative websites of the Animal Welfare Body Utrecht, the Animal Ethics Committee Utrecht and the 3Rs-Centre Utrecht Life Sciences.


At Utrecht University and UMC Utrecht, research in the life sciences (both veterinary and medical-biological) is carried out. Animal experiments are conducted in addition to experiments based on, for example, cell and tissue culture techniques, computer simulations and experiments on human volunteers. Laboratory animals are also used for education and training. All animal use is performed with great care, under supervision of the Utrecht Animal Welfare Body.

Not, unless...

The Dutch Experiments on Animals Act (2014, Dutch only) stipulates that animal experiments may only be carried out if there is really no other option ("not, unless..."). That is, only if there is no animal-free way to achieve the same goal (Replacement). The point of departure is that animals can experience positive and negative emotions and have an intrinsic value. If animal use is inevitable, it is mandatory to see whether that animal experiment can be improved with respect to Reduction of the number of animals and Refinement by, for example, improvement of housing, supervision and procedures. This rule has been elaborated into a set of requirements and steps to take.

From idea to animal experiment

>rom idea to animal experiment


The number of laboratory animals does not equal the number of animal experiments, since on the one hand animals have been re-used in other experiments, and on the other hand animals were bred as laboratory animals without being used in experiments. Both numbers are kept as low as possible and have decreased slightly last year.

i i i The number of laboratory animals is not equal to the number of animal experiments

Number of animal experiments

Grafiek aantal dierproeven

Number of laboratory animals used

Grafiek aantal proefdieren


Almost half of the animal experiments were conducted for fundamental research: research into processes, such as research into the functioning of organs. In fundamental research, the way research outcomes will be applied is not yet clear. The other half consists of applied research, translational research and education. Applied research is research that is directly aimed at an application, for example a specific medical therapy. Translational research connects fundamental and applied research, and often includes translation from results of animal research to clinical application for humans. Finally, laboratory animals are used in education and training, for example in veterinary and laboratory animal science courses.

Animal species

For each research project, the most suitable animal species is used. More than half of the test animals were mice (73%). In addition to mice, rats (10%) were also frequently used, followed by chickens (7%) and zebrafish (6%). Furthermore, cattle, pigs, birds (other than chickens), sheep, horses, donkeys, rabbits and guinea pigs were used, some of them for education.


Discomfort is the legal term for all negative experiences that laboratory animals experience through animal experiments. It is mandatory to classify discomfort into the categories of mild, moderate and severe discomfort, or non-recovery (the animal dies during anesthesia having had no previous discomfort). A permanent effort is being made to keep discomfort levels as low as possible.

Mild: 64%
Moderate: 30%
Severe: 3%
Non-recovery: 3%

Trend in the number of animal experiments

Over the period 2001-2018, the number of animal tests performed by Utrecht University and UMC Utrecht decreased from 51,900 to 19,774. Especially in the period 2010-2014, there was a considerable decrease in the number of animal experiments. Now that ‘quick wins’ in Replacement and Reduction of animal experiments are being applied, the decline is flattening out.

i Trend aantal dierproeven
UMC Utrecht
Universiteit Utrecht

Trend in the number of animals used

Over the period 2014-2018, the total number of laboratory animals used by Utrecht University and the UMC Utrecht increased from 15,087 to 16,240. During 2018 the number decreased for Utrecht University, but increased for the UMC Utrecht.

Trend aantal proefdieren
UMC Utrecht
Universiteit Utrecht

Trend killed without being used

The number of laboratory animals killed without being used in experiments, like excess breeding animals, has been steadily decreasing since 2015, from 27,690 to 15,273 in 2018. During 2018, mouse breeds that were seldomly being used were stopped as living breeds. Some are preserved in the form of frozen cells or embryos.

Trend gedood zonder te zijn ingezet
UMC Utrecht
Universiteit Utrecht