NRP 79 projects – The blind spot in animal experiments: why surplus animals matter

Ethical debates on animal experimentation have focused largely on the pain and suffering caused directly by the experiments, covering issues such as procedures, pain, and severity categories 0 to 3. Much less attention has been paid to the fate of so-called surplus animals. These are animals that are bred for research purposes but never used in actual experiments and are subsequently killed. Although this practice is legal, it raises some fundamental ethical questions.

A recent publication addresses precisely this blind spot. The research team led by Matthias Eggel from the University of Basel argues that both the killing of research animals and the standard housing conditions should be considered as relevant harms in harm-benefit analyses.

In this interview, Matthias Eggel explains the key points from the publication and their significance in the assessment of animal experiments.

What made you decide to focus on so-called surplus animals?

When it comes to debates about animal research, the discussion centres largely on the actual experiments – so on the procedures performed on the animals, and whether they are ethically justifiable. However, very little attention is paid to the fact that many animals are bred but never used in an experiment. Hardly anyone ever talks about these surplus animals, although they make up a significant proportion of the animals affected.

Why has so little attention been paid to these animals in ethical discussions around animal experimentation up to now?

One of the main reasons is legal. Species-appropriate housing and professionally-conducted killing are not classified as harms in legal terms. The severity categories 0 to 3 only apply to animals that are actually used in experiments – in some cases involving a very degree of pain, suffering or distress. So from a purely legal perspective, surplus animals are therefore not subjected to any harm.

People often disregard the fact that around as many surplus animals are killed as are used in experiments. This legal oversight and lack of public awareness partly explain why they barely feature in ethical discussions.

In this publication you argue that the killing of laboratory animals should also be seen as a harm. What does that mean in concrete terms?

The Swiss Animal Welfare Act protects the dignity and welfare of animals. If an animal is excessively instrumentalised, in other words used purely as a means to an end to an excessive degree, this must be justified. At the same time, the killing of animals is not considered a harm in the eyes of the law. Certain killing methods – such as CO₂ euthanasia – are legally permitted, provided they are performed in the proper way by professionals.

We believe that this view is too narrow. First, killing in itself can be considered a harm. Second – and this is key – by being killed, animals are deprived of something: a life. These two aspects support the consideration of killing in an experiment context as morally relevant harms.

If the law assumes that killing doesn’t “take anything away” from an animal, that contradicts our analysis. We believe that the law should be changed so that both experimental and surplus animals are considered as subjected to harm.

What failings do you see in the way current harm-benefit analyses deal with surplus animals?

Surplus animals are effectively omitted from the harm-benefit analysis. This starts with the approval process. On application forms, only the animals that are to be used in the experiment are listed. Surplus animals are left out of the harm-benefit analysis.

This means that overall harm is systematically underestimated. If, for example, 200 animals are used in an experiment, and another 200 are killed as surplus, the ethical assessment would only list the 200 animals used in the experiment. The surplus animals are not subjected to any experimental procedures, such as surgery or injections, which means the harm is smaller – but it is still morally relevant.

The more moral weight we attach to an animal’s life or death, the greater the pressure to minimise the breeding and production of surplus animals.

How can your work contribute to the implementation of the 3R principles, particularly in the area of reduction?

The traditional interpretation of ‘reduction’ does not necessarily mean reducing the number of animals. Rather, it is about using only the number of animals that is statistically required to achieve a specific research goal.

There is a broader perspective, however, that seeks to reduce the overall number of animals used. This can lead to some conflict between the principles of reduction and refinement.

For example, an experiment could be conducted with ten animals, which are used repeatedly and therefore suffer greater harm. Alternatively, you could use 20 animals, with each one suffering less harm. The overall harm would be comparable, but is distributed differently.

The refinement principle would favour the option with more animals and less pain and suffering for the individual animals. On the other hand, a strict reduction perspective would go for the option with fewer animals but greater harm. But if we assume that death itself is a relevant harm, the question of how many animals die altogether becomes more important. In that case, the option with fewer animals may be preferable.

Ultimately, this requires careful analysis of each individual case. The harm-benefit analysis would be a suitable instrument for this – provided that death is recognised in it as a harm. This would require a corresponding change in the law.

What specific changes to research practice would you see as realistic in the short term, and what would be the next steps to sustainably improve the situation of research animals?

In the short term it would be realistic to optimise the number of surplus animals where this is not yet sufficiently done. This also includes refining the approval procedure so that the harms of surplus animals are systematically taken into account.

In addition, a research project – commissioned by the federal government, including the Federal Food Safety and Veterinary Office – is looking at killing methods. Although Switzerland has relatively strict legislation, there is still room for improvement – for example in terms of housing conditions.

Our work should help ensure that surplus animals are no longer overlooked in ethical assessments. Because if they do not even feature in harm-benefit analyses, the actual harms caused by animal experiments may be underestimated.