Discomfort during animal testing

Whenever animal testing is necessary, TNO and Triskelion BV aim to ensure as minimise discomfort as possible for animals without compromising the quality and applicability of the study results. We have animal welfare uppermost in our concerns, hence both TNO and Triskelion BV have an AAALAC accreditation. In most studies the laboratory animals suffer mild or moderate discomfort. Where possible, we try to reduce discomfort, for example by choosing advanced humane end points, better test methods or the use of analgesia. In a limited number of studies, animals are anesthetised for the purpose of the study, without the necessity to awaken them. This way, discomfort of these animals can be kept to a minimum. Internationally, this type of study is classified as ‘Terminal’. For TNO, the number of ‘terminal’ animal experiments comprises 2%; at Triskelion B.V. this type of studies was barely conducted in 2016 (in total 3 animals).


All other animal experiments are classified as mild, moderate or severe.

AAALAC (Association for Assessment and Accreditation of Laboratory Animal Care) is a worldwide accepted organisation that aims to optimise animal welfare through a voluntary accreditation and assessment programme that extends beyond the minimum regulatory requirements for animal testing.

MILD discomfort (70% of animal tests at TNO and 52% at Triskelion BV)

For some studies animals must be fed a special diet, such as a high or low-fat diet, which cause no inconvenience. This type of test may be a treatment that is categorised as 'mild discomfort'. TNO aims to reduce the number of animals needed by choosing an optimum statistical design and combining control groups where possible.
At Triskelion BV animals are exposed to substances to establish the toxicity. This is a legislative requirement for each substance to which humans are exposed, with the exception of ingredients for cosmetics. The aim of such tests is to establish the dose at which no toxic effects can be observed. In most cases the animals suffer mild discomfort. Occasionally, substances are toxic and the animals suffer more discomfort. To ensure that a minimum number of animals experiences this higher discomfort , for substances about which there is little information available, only a small number of animals is tested to ascertain the right dose before the main regulatory study is performed.

Moderate discomfort (27% of animal tests at TNO and 39% at Triskelion BV)

For other studies the animals are injected with the substance under investigation on a weekly basis over an extended period, or light surgery is performed under anesthesia. If possible, procedures are combined to reduce the number of animals subject to such intervention. Painkillers are also used for animals that undergo light surgery. Such experiments come under the ‘moderate discomfort' category and concern, for instance, studies with mice whereby a piece of skin from a patient with a skin disease is transplanted. The skin disease remains present in this piece of skin and may be used to test new drugs.
In toxicological studies repeated exposure to a substance may result in moderate discomfort, such as repeated exposure to substances to which humans are exposed through the lungs. Rats are used for this type of research for several hours over a number of days, secured in a tube so that the nose is in contact with an airflow in which the test substances is dissolved. In 2010 TNO modified the tubes in such a way that the animals suffered less discomfort during exposure.

Severe discomfort (2% of animal tests at TNO and 9% at Triskelion)

Testing the efficacy of drugs involves testing the potential new drugs in animals in which a specific disease is induced, which may result in ‘severe discomforts' in the animal. For example, TNO tests new drugs for lungfibrosis and Triskelion BV tests new drugs for auto-immune diseases, such as arthritis (rheumatism), multiple sclerosis and influenza (vaccine testing). In recent years the number of influenza epidemics is rising, leading to an increased demand for the development of novel vaccines. For this, simulation of this serious disease is necessary to test the efficacy of the vaccine. In these studies we choose the earliest possible experimental end point to ensure that the test can be stopped as soon as acceptable results are achieved.


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