Animal use for scientific purposes raises ethical issues, whatever the level and nature of any suffering involved. Procedures that can cause severe suffering are of particular concern and the justification for using these deserves special scrutiny.
man presenting


Many regulatory systems use a harm-benefit analysis to examine the justification for research projects, where the likely harms to animals are considered against the potential benefits of the research. Where suffering may be high, the expected benefit must be proportionately high, but the aim should always be to avoid severe suffering wherever possible.

“Where severe suffering is unavoidable, there should be an exceptionally high level of benefit and likelihood of achievement.”  UK Animals in Science Committee

The UK Home Office recognises that severe suffering is of particular ethical concern, and requires special justification for project applications involving severe suffering. Projects including severe procedures on ‘special’ species (dogs, cats, primates and horses) must be referred to the national committee; and all projects involving severe protocols must undergo a retrospective assessment. UK and EU legislation also includes an absolute upper limit to harm – ’long-lasting, severe pain, suffering or distress that cannot be ameliorated is not permitted’.

Ethical Issues

A key factor in the harm-benefit analysis and ethical evaluation of any project or procedure involving severe protocols is its translational, or predictive, value. If a severe protocol is believed to be necessary for an animal ‘model’ of a serious human disease, to reproduce the severe suffering seen in humans, then from an ethical perspective the results must be translatable. But there are many examples in the literature where potentially severe models (e.g. rodent middle cerebral artery occlusion in stroke research) have poor predictive validity, i.e. medicines that work in preclinical trials fail to provide benefit in clinical trials.

Possible reasons for translational failure include poor pre-clinical experimental design, inappropriate animal ‘models’, inherent species differences and heterogeneity of patients in clinical trials. Whatever the reason, the justification for severe suffering is compromised if translation is poor. Similarly, if any model generates a long series of published papers, but these do not lead to new therapies in the clinic, at some point it will no longer be ethical to continue that line of research.

Some questions that AWERBs or equivalent committees may like to ask:

  • Why is severe suffering needed?
  • What is being done to reduce/avoid this?
  • Are the benefits sufficiently high to justify the suffering?
  • Can you demonstrate that the model is translatable?
  • Could the protocol be run with a moderate severity limit?
  • What if we said ‘no’’?
  • Welfare Assessment

Many other questions relate directly to benefit and have a bearing on the justification for severe procedures. For instance, could a particular clinical issue be resolved more rapidly and effectively via human behaviour change protocols, ‘social prescribing’, or policy changes, than with a new medicine? Is there a good level of dialogue with relevant clinicians, to ensure that the proposed benefits are realistic and actually wanted and needed in the field? For ‘basic’ research in which suffering may be severe, how much weighting should be given to human knowledge and interest, without an immediate applied medical benefit?


There is wide agreement on the need to reduce severe suffering using the 3Rs. However, there may be differing perspectives on the more challenging questions around benefit and ‘need’ as set out above, and about the ethics of going ahead with the research, and it is important to accept and address these. (See ‘Doing ethics’, appendix 2 of the RSPCA Lay Members’ Resource Book).

In the UK, an ideal forum for discussing such issues is the local, institutional Animal Welfare and Ethical Review Body (AWERB). One of its functions is the provision of a forum for discussion and development of ethical advice, which is an ideal place to discuss how severe models and procedures will be reviewed and refined within an establishment and decisions made. Outside the UK, the AWB, IACUC, AEC and other ethics committees can convene these kinds of discussions.

Opening the issue up to wider consultation enables additional in-house expertise and viewpoints to be included. When all perspectives are taken into account, it might be decided to define the types of benefit and purpose for which severe protocols may, or may not, be permitted within the institution, or to mandate that all potentially severe procedures are managed to not exceed ‘moderate’ via the use of humane endpoints.

Other issues that could be considered as part of an ongoing ethical discussion are: whether it is more, or less, ethically acceptable to use animals of certain species in severe protocols, and why; and how people within the institution actually interpret the concept of ‘severe’; for example, views about ‘harms that ought not to be done’ and ‘naturalness’ may be important to staff. Holding these discussions outside of project application review can allow views to be more freely expressed and ensure that the establishment’s individual culture is defined and understood.

More information about ethical review can be found on the RSPCA website.


Avoiding and reducing severe suffering helps to fulfil legal requirements, reduce ethical concerns and improve scientific quality - this website will help you to achieve this.

Practical ways to reduce or avoid severe suffering include: