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Why do scientists conduct experiments on animals at all? Can we do without animal experiments? What alternatives are there to animal testing and how can we make animal testing better for animals? Our FAQ section answers all these questions.

What are medical animal experiments?

The German Animal Welfare Act defines animal experiments as "interventions or treatments for experimental purposes on animals, if they can be associated with pain, suffering or harm to these animals". This includes experiments in which scientists alter the genetic material of an animal, as well as the breeding of genetically modified animal lines. In most cases, animal experiments serve to answer a scientific question. In particular, these involve basic research, the investigation and treatment of diseases (in humans and animals), and legally required toxicity and safety testing of drugs and chemicals.

In addition, there are animal experiments that are not directly related to a scientific question. These include procedures or treatments on live animals for education, training, and continuing education purposes (for example, in laboratory animal science education and veterinary medicine), as well as the production and propagation of substances, products, or organisms when they are needed for research (such as antibodies or parasites).

If, on the other hand, researchers kill an animal in order to remove organs, cells or tissue from it for scientific purposes, this does not count as animal experimentation according to the Animal Protection Act.


Which animal experiments are permitted?

Animal experiments may only be carried out if they have been approved by the
have been approved by the relevant authorities. In the application for approval, which is already at least twelve pages long without being filled out, scientists must provide comprehensive scientific and ethical justification for the planned experiment.

They must explain what new knowledge will be gained with the animal experiment, that the question is new and has not yet been clarified by an animal experiment. In particular, it must be conclusively demonstrated that the objective of the project can only be achieved with an animal experiment. This requires that the applicant has prepared thoroughly for the research topic and has also considered the possible stress on animals in his justification. The ethical evaluation is also supported by the proof that, in the sense of the 3Rs, the experiment cannot be replaced by alternative methods (replacement), that the number of animals used is reduced to a minimum (reduction), and that the stress on the animals is kept as low as possible (refinement).

In addition, there are laws at both German and EU level that regulate in detail which requirements must be met for the keeping and care of animals and for an animal experiment. Detailed information on the legal basis can be found here.


Why are medical animal experiments carried out?

The most important reasons are basic research to better understand life processes and diseases, to develop new medicines and cures, and to test the safety of drugs and other substances with which humans come into contact.

Through basic research, scientists gain knowledge about how the complex organism of living beings works. Only through this can they understand what processes take place in the body when it is diseased. This is the basic prerequisite for developing or improving new drugs and therapies. Scientists use animal experiments in basic research because numerous cell processes function in exactly the same way as in humans. Vital functions can also be easily compared in many cases, such as hearing, vision, movement, breathing or digestion. The complex structures of our organism can already be studied using mice, for example the
nervous and immune systems. Not only the similarities but also the differences between the various organisms can contribute to the scientists' knowledge.

Numerous diseases occur in both humans and animals. Scientists can therefore use animals to study very well how the diseases affect the body. These findings, in turn, can be the starting point for the development of drugs and therapies.

Animal experiments are needed to develop and test new drugs and therapies. To date, numerous medical achievements can be traced back to them. Without animal experiments, for example, there would be no pacemakers or hip prostheses today. Numerous surgical techniques were also first tested on animals.

Before drugs are approved for use in humans, scientists use animals to study the good and bad effects of an active ingredient on the organism. In many cases, these studies are required by law.
In addition, animal testing provides further information about the efficacy and correct dosage of an active ingredient.


Why can't we replace all animal experiments?

Research into alternative methods now plays a major role in science and is supported by various bodies, such as the Central Office for the Documentation and Evaluation of Alternative and Complementary Methods to Animal Experiments (ZEBET).
(ZEBET) - is specifically promoting this research. Through the use of computer simulations or cell cultures, researchers can nowadays dispense with animal experiments in many areas. Nevertheless, there are limits to these methods, especially when researchers want to understand complex physiological relationships of the entire organism. For example, alternative methods can be used to test how a drug affects a cell culture, but not how it affects other cell types or whether it causes degradation products that may damage organs.

Other examples include the mode of action of the central nervous system, the processing of sensory stimuli or the interaction of the circulatory system. Even the interconnection of organs and tissues cannot yet be artificially reproduced. Animal experiments are therefore often irreplaceable, especially for research into complex life-threatening diseases - such as cancer, HIV, diabetes mellitus, malaria or Alzheimer's disease.


What does the abbreviation "3R" stand for?

The principle of the "3Rs" was postulated in 1959 by the British scientists William Russel and Rex Burch. The "3Rs" stand for the reduction (Reduction) and refinement (Refinement) of animal experiments and the development of alternative methods (Replacement).
Russel and Burch published their three principles, which today serve as an important ethical guidelines for all biomedical research, in the book "The Principles of Humane Experimental Technique". The principles show what researchers must consider when designing an ethically acceptable animal experiment.


How can we replace animal experiments?

The goal of researchers is to replace as many animal experiments as possible. New alternatives are constantly being developed and methods tested with which this can be achieved. We would like to briefly explain two of them here. Namely, the so-called "in vitro" and "in silico" procedures. In the first method, we observe living cells within an artificial environment, for example in a Petri dish. This can have two major advantages: First, living organisms do not always have to be harmed. Second, the results obtained can be understood more easily. This is because very complex processes take place in a living organism at all times, often simultaneously. These processes cannot simply be switched off for an experiment. To understand the results, it is important to have ruled out all other explanations. This is easier in a controlled environment. Here, one can determine exactly which processes are to take place and which are not. Three in vitro models are particularly important for researchers: permanent cell cultures, organoids and multi-organ chips. Permanent cell cultures are simple collections of cells. These cells continue to divide as often as desired and can therefore be used for a very long time. For example, researchers can test how a particular type of cell responds to an active ingredient. Organoids are more advanced in comparison. They can even resemble human organs in the way they function. Organoids allow researchers to test, for example, how a particular organ might respond to an active ingredient. This is because organoids can simulate individual functions of human organs. Multi-organ chips are several of these organoids that have been linked together. This allows even more precise investigations to be carried out. In-silico methods are computer-based alternatives. These can be, for example, elaborate simulations. These simulations can be "fed" with data that have already been obtained. In this way, the computer learns about the properties of certain cells and can predict possible reactions.

How can we reduce animal experiments?

Unfortunately, it happens that animal experiments cannot be replaced because there is no alternative yet. In such cases, researchers should reduce the number of animals used in their experiments to the absolute minimum. This can be achieved by several strategies. The goal of any animal experiment is to obtain a meaningful result. Basically, the more animals you use for an experiment, the more accurate the results will be. If too few animals are used for an experiment, this can be problematic. There is then the risk that the results are arbitrary. This would not be good. The results become more accurate with the number of animals used. However, only up to a certain number. Once this number is reached, the results can no longer become more accurate. This number of required animals can be different for each experiment. With the help of statistical methods, this number of animals can be precisely calculated and thus reduced. This ensures that no more animals have to be used for an experiment than are actually needed. In addition, researchers are also required to develop a well thought-out study design prior to their experiment. To do this, researchers can search the scientific literature for similar experiments. If they find them, problems, for example, could be identified early on. In this way, researchers can identify potential problems before the experiment. This gives them the opportunity to improve their study design if necessary.

How can we refine animal experiments?

Not all animal experiments can be replaced yet. But the animal experiments that are nevertheless necessary can at least be improved. This can be achieved by reducing the stress for the animals. Both during the experiment and in the husbandry. Thus, the laboratory animals are exposed to less stress. For example, some additional toys in the cage to pass the time or certain holding and handling techniques can already help to reduce the stress of the laboratory animals. This is not only good for the animals, but also for us. Because this can also have a positive effect on the significance of the results. Stress is indeed capable of influencing the results of experiments. The consequence could be that they are more difficult or even impossible to interpret. Researchers should also plan their animal experiments carefully. They should consider which experimental method and which animal species are best suited for their experiment. When choosing these two aspects, they should of course always be mindful of causing as little suffering as possible.

Why cannot we replace all animal testing?

Unfortunately, the state of science does not yet allow us to replace all animal testing. As mentioned above, many alternatives have already been developed and new methods are constantly being added. However, animal experiments are sometimes unavoidable for scientific reasons. Namely, when a scientific question is to be answered, but no alternative has been developed for this purpose yet. However, it should also be mentioned that the expected benefit of an animal experiment must be greater than the suffering caused. Otherwise, this experiment would not be approved.


Tierschutzgesetz (TierSchG) | Animal protection law:

The Principles of Humane Experimental Technique: Russell/Burch, 1959.

Free readable new edition from 1992:

Tierversuche verstehen. Eine Informationsinitiative der Wissenschaft (Understanding animal experiments. An information initiative of science):