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Severity degrees, numbers & statistics

Severity degrees of animal experiments

Legal framework An animal experiment is only permitted by law if the animal´s prospective pain, suffering or harm is ethically justifiable in regard of the purpose of the experiment.

The indispensability of each individual planned animal experiment must be examined and assessed against the expected stress for each individual animal. The following principle applies: the greater the expected burden on the animals, the greater the scientific benefit must be.

The expected burden on the animal is scientifically assessed and checked for ethical justifiability. The burden is not determined by the applicants. Instead, the researchers provide a personal severity assessment, which is critically reviewed by the animal welfare officers and then submitted to the approving authority. The authority then determines the final exposure of the animals for each experiment.

European determination of load levels According to European legislation, a classification is made between the degrees of stress ‘mild’, “moderate”, “severe” and ’no recovery of vital function’.

When planning the experiment, care is taken to ensure that the severity imposed on the individual animal is kept as low as possible. The degree of severity for the overall experiment is determined according to the highest stress to be expected for the individual animal. This means that even if other groups of animals in an experiment are not exposed to stress (e.g. control animals), the entire experiment is still considered to be severely stressed if an individual animal can experience this stress.

Definitions of the Severity Degrees

‘No recovery of vital function’: This term is used for procedures that are performed entirely under general anaesthesia, from which the animal does not wake up, or when animals are killed for scientific purposes for subsequent organ removal (without prior treatment, intervention or manipulation). The latter accounts for by far the largest proportion of animals killed for experimental purposes and, although it is not considered an animal experiment according to the Animal Welfare Act, it is included in the annual laboratory animal report as the degree of stress ‘no recovery of vital function’.
‘ Mild’: Procedures that cause minor pain, suffering or harm to animals for a short period of time or do not cause significant impairment of the welfare or general condition of the animals are categorised as ‘mild’.

Example: The subcutaneous injection of a drug.

‘Moderate’: Procedures that cause short-term moderate pain, suffering or harm to the animals or prolonged minor pain, as well as experiments that cause moderate impairment of the welfare or general condition of the animals, are classified as ‘’moderate‘’.

Example: The administration of anaesthesia with subsequent awakening.

‘Severe”: Procedures that cause severe pain, suffering or distress to the animals or prolonged moderate pain, suffering or harm, as well as procedures that cause severe impairment of the welfare or general condition of the animals, are classified as “severe”.

Example: The induction of a clinical disease associated with partial paralysis.

Numbers & DRFZ Statistics

In Germany, a total of 2.13 million vertebrate animals were used for scientific research in 2023. This means that the number of laboratory animals in Germany has fallen compared to the previous year (2022: 2.44 million). The total number of animals includes 1.46 million animals used in animal experiments and 672,000 animals that were killed for scientific purposes without prior animal experimentation. Rodents, especially mice and rats, accounted for by far the largest proportion of all laboratory animals, at around 80 %.
The use of a total of 133,091 laboratory animals in Berlin was reported for 2023, which is around 23 % less than in the previous year (173,470 animals in 2022).

Berlin has long been known as the ‘capital of animal research’. However, the high number of laboratory animals can be explained by the high density of research institutions.

In 2023, 3648 animals were used for scientific research at the DRFZ. The number has increased compared to the previous year (2215 animals), but is in a similar range to 2021 (3598 animals).

Did you know: For many experiments, it is necessary to determine the genotype of each animal born in order to ensure that only those animals in which the desired genetic modification for the respective scientific question has been inherited are selected for the experiment. In most cases, typing can be carried out from ear punch samples, which are collected during the individual marking of the animals in everyday animal care. However, some characteristics can only be determined by analysing blood samples. In the European Union, taking blood samples for this purpose is classified as animal experimentation. This means that the number of laboratory animals quickly increases when a new experimental project begins at an institute in which all bred animals have to be typed in advance by taking blood samples. This is also the reason for the strong fluctuations in the number of laboratory animals at the DRFZ in recent years. While one project ended in 2021 due to the need to determine the genotype, a new project was started in 2023.

Further information on the number of laboratory animals

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