At what point must you euthanize an animal in scientific research?

In this day and age, there are several areas of research using animals to propel scientific and medical advancements. Animal research has provided a stable foundation for the growth of basic and applied sciences. And, despite the modern development of alternative research methods, there is currently no replacement for animal (e.g. rodent, non-human primate) research [1].

Across all areas of scientific research, there are fundamental regulations put in place to protect the welfare of animals. There is a legal and ethical obligation to minimize an animal’s level of stress and suffering. Ultimately, these obligations limit the number of animals in scientific research and protect those which are bred and used for science.

Care for research animals stems from the 3Rs principle of refinement, replacement and reduction [2]. For example, continuously refining animal husbandry (housing) to support cognitive and social enrichment and working to reduce the number of animals in research. While it is forward-thinking to implement methods that may replace animals in scientific research, at this point in time, not all animal models can be replaced by an alternative. Therefore, it is important to treat research animals well, especially if they become ill or exhibit any pathological condition. In the end, an animal would not perform well under stressful or unhealthy conditions. Therefore, the well being of the animal is not just obligatory in terms of animal welfare, but also necessary to obtain reliable results. Scientific accuracy and reproducibility is contingent upon an animal’s well being.

In early 2018, a decision was made by the local prosecutor’s office in Tübingen, Germany to press charges against the scientists responsible for a particular non-human primate research project at the Max Planck Institute for Biological Cybernetics. The case, provoked by the September 2014 release of an emotionally-charged video of the animal facilities, compiled by an undercover animal rights activist, has been ongoing since the animal rights organization filed a misconduct lawsuit against the research department in 2015. The charges are related to the timely euthanasia of three research animals, a decision heavily weighted by ethical ramifications and the realization of the animal’s health and well being. But, at what point must you euthanize an animal?

Special considerations must be made when conducting research with animals. Scientists must adhere to pre-defined ethical and legal criteria, which describe the potential impact of experimentation on an animal’s health and well being. These ethical and legal criteria regulate the experimental procedures, e.g. appropriate method use, animal treatment and when an experiment should be aborted. These regulations, as outlined by law, are specific to the animal model and the research question. The persons responsible for the experimental conduct  (i.e. animal welfare officer(s), veterinarian, and scientist) must exert their expert opinions and monitor the lawful execution of research studies.

While the main scientist responsible (e.g. the Principle Investigator), considers the effect of the injury on the scientific outcome, he also takes into account the legal and ethical measures as outlined by the research protocol. Additional input from a trained veterinarian and animal welfare officer aids in assessing the animal’s well being and the potential for treatment. From an ethical and a scientific standpoint, an injured animal should be treated as long as recovery is evident. Recovery and rehabilitation depend on the feasibility of treatment, chances of success, personnel, resources, etc.  The difficult question then arises: how much effort should be devoted to the treatment and rehabilitation of an injured or ill animal? And also, how well the animal copes with the treatment and/or rehabilitation. The opinion of a medical expert, such as a veterinarian, is crucial for the decision of whether, and how long, to treat an animal. In the case of treating somebody’s pet, a veterinarian may outline the criteria for euthanasia, while the pet’s owner tries everything she can to save the pet’s life, even if treatment options are bleak. A veterinarian can provide his medical opinion, but the decision ultimately lies with the pet’s owners, or in the case of scientific research, the Principal Investigator and the animal welfare officer.

Overall, all possible treatment options should be exhausted before considering euthanasia and the end of an animal’s life. These are just some of the points to consider when contemplating animal treatment and euthanasia.  

A local regulatory commission (Regierungspräsidium) is responsible for reviewing, approving and monitoring the progress of animal research protocols. Legally approved studies are required to comply with protocol criteria (e.g. length of study, significant number of animals, experimental time-frame, expected outcomes and potential risks, criteria for treatment and euthanasia) defined a priori. This regulatory commission reviews the adherence of protocols to the standards of ethics as defined by the local ethics commission and also internationally by, for instance, the European Union. Therefore, before a protocol is approved, the principal scientific investigators must acknowledge the applicable criteria listed in the 2010/63/EU directive and have the appropriate qualifications to administer lethal substances, as such used for euthanasia. Also, the protocols must contain a description of criteria under which euthanasia must be seriously considered.    

Overall, the matter of animal welfare in science is not a matter to address lightly. Successful research endeavors are dependent upon the well being of its animals. Additionally, the decision of whether to treat or euthanize an animal is not always black and white; context-specific and medical factors play a large role in the decision made. Even with the inclusion of expert opinions and experience, the euthanization of an animal is never an obvious decision. This is in no way different from the difficult decisions made in every veterinarian’s practice for pets or for doctors and their patients suffering from severe medical ailments. Responsible persons have an ethical and moral responsibility to consider all options of treatment and determine the amount of effort invested into restoring health before the permanent option of euthanization.


  1. White Paper: The Critical Role for Non-Human Primates in Medical Research. 2016
  2. Directive 2010/63/EU of the European Parliament and of the council. Official Journal of the European Union.

    The images were created by Anastasia Illarionova.

Renee Hartig
is currently
a GTC doctoral student in Neuroscience in Tübingen.

Felicitas Horn is currently a GTC doctoral student in the Functional and Comparative Neuroanatomy Lab of Dr. Henry Evrard in Tübingen.


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