Not all experimental animals are necessarily in pain. However, in animal experiments, all animals suffer some sort of discomfort. Discomfort can include several types of suffering, not only pain but also stress, fear, loneliness, and lasting injuries.
The discomfort will be scaled into four categories: mild, moderate, severe and terminal. The determination of this classification is based on the severity, duration, and frequency of the discomfort.
Mild: Short-lasting mild discomfort
Example: A study in which the animals receive a dietary supplement via the food and a few blood samples are taken.
Moderate: Short-lasting moderate discomfort or long-lasting/frequent mild discomfort
Example: A surgical procedure under general anaesthesia with adequate pain medication or multiple blood samples.
Severe: Short-lasting severe discomfort or long-lasting/frequent moderate discomfort
Example: A tumour induction to test a new cancer treatment or multiple surgical procedures under general anaesthesia with adequate pain medication.
Terminal: The experiment is performed under general anaesthesia, from which the animal will not recover.
Example: The animal receives an anaesthetic overdose. Right before the animal dies, when it is sedated and does not feel any pain, tissue samples are taken. This technique is only performed in case it is not possible to use tissues from dead animals.
It is prohibited by law to perform animals experiments in which the animals will suffer a long-lasting severe discomfort. In order to prevent long-lasting discomfort, humane endpoints are being used.
We try to avoid that the animals suffer pain as much as possible. We do this, of course, because this is the right thing to do from an ethical point of view but also because pain can have an effect on test results. Therefore, the researchers are trained in pain recognition in order to detect signals of pain in time and treat it with painkillers.