Animal Use Statistics
Each year, all UK research establishments must report the previous year’s number of regulated procedures on protected animals. This is known as the “Return of Procedures”. The Home Office collates and publishes these numbers in a report entitled the “Statistics of scientific procedures on living animals”.
The Animals (Scientific Procedures) Act 1986 (ASPA) defines protected animals as any living vertebrate, other than humans, and any living cephalopod.
The LMB works with Understanding Animal Research to publicise the annual Return of Procedures in the #AnimalStats campaign.
Animal species used in LMB research programmes
Mice and rats are used in LMB research programmes. The following table shows the number of procedures recorded for mice and rats from 2022‑2024.
| Type of Animal | 2022 | 2023 | 2024 |
|---|---|---|---|
| Mouse | 56,067 | 52,292 | 51,926 |
| Rat | 6 | 20 | 77 |
| Total | 56,073 | 53,312 | 52,003 |
Severity of Regulated Procedures
ASPA regulates procedures carried out on protected animals for a scientific purpose. Procedures can only be conducted if approved by the Home Office and staff have been trained and assessed as competent.
The annual Return of Procedures also includes a report on the severity of each procedure conducted on animals. Severity thresholds are divided into five categories: subthreshold, mild, moderate, severe and non-recovery. In 2024, procedures at the LMB fell into the following severity thresholds.
The majority of regulated procedures conducted at the LMB involve breeding and are thus classified as subthreshold.
An explanation of severity levels
Subthreshold: the procedure has little impact on the animal’s welfare.
For example, breeding healthy genetically-modified animals or handling animals to give them a routine health check. The majority of regulated procedures conducted at the LMB involve breeding and are thus classified as subthreshold.
Mild: a procedure that may result in slight transitory or minor pain, which the animal recovers from within a short period of time.
For example, an injection of a hormone to induce ovulation or an injection associated with taking a small blood sample.
Moderate: a non-life threatening procedure in which the animal is likely to experience short-term moderate pain, suffering or distress.
For example, a surgical procedure carried out under anaesthesia with pain relief given. A common example of this would be surgery undertaken to implant genetically-modified mouse eggs into a female recipient mouse.
Severe: the procedure causes a major departure from the animal’s usual state of wellbeing.
The Home Office requires all unexpected animal deaths to be reported as severe, regardless of the protocol under which the animal is held. For example, sometimes the first litter from an inexperienced mother will not thrive as well as future litters and some pups could die.
Non‑recovery: the entire procedure will be carried out under anaesthesia and the animal will be humanely killed without regaining consciousness.
For example, if a large volume of blood is required for analysis at the end of a protocol.
Research Topics
LMB researchers use animals to investigate a diverse array of topics.
In particular, genetically-modified mice are invaluable for the study of whole-body systems, including research into diverse diseases and health conditions such as asthma, neurodegenerative diseases such as Alzheimer’s, Parkinson’s and Huntington’s and cellular processes which, when dysregulated, can lead to cancers.