Every year, millions of scientific procedures are carried out on animals in Great Britain for the purpose of scientific research. Here we give some insight into what a ‘procedure’ is and how they are classified. We also explain what types of research may involve procedures on animals.

Every year the UK Home Office publishes a report of the ‘Annual Statistics of Scientific Procedures carried out on Living Animals, Great Britain.’ This report provides an overview of what animals were used, how they were used, where they were used and for what purpose. This reporting is a legal requirement under the Animals Scientific Procedures Act 1986 (ASPA) and is an important aspect of transparency in animal research. ASPA regulates the use of live animals in any experimental, testing or research procedure covered by the legislation.

In Great Britain, animal research statistics are recorded as the number of procedures conducted, or number of ‘uses’ rather than the number of individual animals used. This is because, under certain circumstances, animals can be reused in more than one procedure.  This means that the actual number of individual animals used each year remains unknown but will be slightly less than the number of procedures. An animal being reused for more than one procedure depends heavily on the severity classification of the procedures they were used in before.

What is a procedure? 

According to the most recent Home Office statistics, in 2021, 3.06 million regulated procedures were carried out on protected animals in Great Britain. A regulated procedure is defined as any procedure applied to a protected animal for a qualifying purpose, in other words, for any scientific, research, testing or educational purpose covered by ASPA, that may have the same effect, or higher, than the introduction of a hypodermic needle in accordance with good veterinary practice. If you have had an injection or blood taken you will know that having a needle inserted through the skin is not pleasant – any procedure considered to cause an animal a similar or greater level of pain, suffering, distress or harm than this is classified as a regulated procedure and is covered by the Act.

Regulated procedures are very varied and aim to cover all scenarios where animals may potentially experience pain or suffering. It must be noted that there is a legal requirement for researchers to put in place measures to minimise pain and suffering to animals in their studies in accordance with the 3Rs, but due to the nature of the procedure or the research, this cannot always be fully addressed. An example might be administering pain relief if this can be done without affecting the outcomes of the research.  Examples include administering drug doses, taking samples, administering anesthetic, surgery to remove tissue under general anesthesia, withholding food or water or breeding animals with harmful genetic defects.

Which animals are protected by ASPA?

Protected animals are those species covered and reported on under ASPA. This includes all vertebrate species (animals with a backbone) and, in 2012, the Act was amended to also cover cephalopods – a group of invertebrates (no backbone) including octopus, squid, and cuttlefish. Protection also extends to the embryonic stages of these animals once they have developed to a point where they can experience pain or suffering. The times and stages for this in different species is set out in ASPA guidance.

Why are some species not covered?

ASPA is specifically set up to protect ‘sentient’ species. Sentience is the ability of an animal to feel pain but also experience or suffer as result of that pain, so essentially sentient species can experience feelings such as fear or distress. Whether an animal is sentient or not is based on various evidence including the complexity of its nervous system, the way it interacts with its environment and other members of the same species, and other specific evidence.

Other invertebrate species such as the fruit fly or worms, both of which are commonly used in biomedical research, are not considered sentient and are therefore not protected under ASPA. There is however mounting pressure to add the invertebrate group that includes lobster, crab and crayfish (decapod crustaceans) in light of increasing evidence of their sentience.

Horses, cats, dogs and non-human primates are classified as ‘specially’ protected species, due to their increased capacity to suffer in a research environment. To use these animals in research, the license holder must show that no other species was suitable for the purposes of the license work and must adhere to the license conditions.

What purposes are procedures carried out for?

The 3.06 million procedures performed in Great Britain are split into two broad categories – experimental procedures, and procedures for the creation and breeding of genetically altered (GA) animals.

Experimental procedures are procedures that involve animals for the purpose of scientific studies, development of new drugs, treatments and medical devices, safety testing of chemicals and drugs, surgical training and education, and these can be for general biological research, human medical research or veterinary research. Environmental research and species protection can also fall under experimental procedures, if they involve research on animals.

All these experimental purposes are classified for the reporting of the statistics into three main categories:

Basic research (also known as fundamental research) – Basic research is conducted primarily to expand knowledge of a subject area. This can include structure, functioning and behaviour of living organisms. Unlike other branches of research, basic research does not aim to solve specific problems with its outcomes, but rather improve on understanding. It helps improve knowledge of how different tissues and organs work and helps identify potential new drugs. The most common areas of focus for basic research using animals are the immune system, nervous system, and cancer.

Applied research – Applied research is used to find a solution to a specific issue or problem. This research attempts to address diseases through prevention and the development of new drugs. The most common areas of focus are human cancer, human infectious disorders, human nervous and mental disorders.

Translational research – This is similar to applied research, and in the reporting of animal research statistics, is often grouped with applied research. There is no universally accepted definition of translational research, however it is accepted as bridging the gap between what is learnt from basic research and the practical applications of applied research.

Regulatory testing – These are procedures that are carried out to meet a legal requirement, to ensure that products are safe for use. This includes making sure that substances used in food, agriculture and household products meet legal specifications for safety, and evaluating the safety or effectiveness of pharmaceuticals and veterinary medicines. The most common areas of focus are routine production, toxicity and safety testing, and quality control.

In recent years, the highest uses of animals for experimental purposes have been for basic research, closely followed by applied research, with procedures for regulatory research generally being much lower.

Around half of all procedures currently are for the experimental purposes set out above, the other half are carried out for the purpose of creating or breeding GA animals. This involves breeding animals that have mutated or modified genes in order to produce GA offspring for use in experimental procedures. These animals are not used in experimental procedures themselves.

How is the harm of a regulated procedure assessed?

ASPA requires a harm-benefit assessment to be conducted as part of the license application to carry out animal research. This is the process of considering the likely benefits and value of the research against the likely harms the animals will experience, to determine whether the likely harms are justified. To assist with the harm benefit analysis the legislation also requires all procedures to be classified according to their severity.

There are four severity classifications: non-recovery, mild, moderate and severe.

Non-recovery is defined as a procedure that is performed under general anesthesia from which the animal will not recover consciousness.

Mild is defined as a procedure that will likely cause short-term, mild pain, suffering or distress to an animal, but with no significant impairment of their overall wellbeing or condition.

Moderate is defined as a procedure that will likely cause short-term moderate pain, suffering or distress to an animal, or long-lasting mild pain, suffering or distress. These procedures are also likely to cause moderate impairment of their wellbeing and condition.

Severe is defined as a procedure that will likely cause severe pain, suffering or distress to an animal, or long-lasting moderate pain, suffering or distress. These procedures are also likely to cause severe impairment of their wellbeing and condition.

Severity classification is decided based on the most severe effect a procedure could possibly have, when taking into account all factors. For an animal to be reused in more than one procedure, the procedures in which they are being reused must be either mild, moderate or non-recovery. Under no circumstances can an animal be reused in procedures classified as severe. A veterinary surgeon with knowledge of the animal’s life and experience must also advise on whether the general state of health and well-being is likely to be completely restored from the previous procedures conducted, before being used in a new procedure. Consent to reuse an animal must be given by the Home Office and must be authorised through the necessary project license.

You can read more about ASPA and legislation on the use of animals in other countries here.