In June 2023 it published a report looking at the forced swim test (PDF, 504 KB). The report makes recommendations around:

• specific scientific justification for future use of the forced swim test
• purposes for which the forced swim test should not be used
• the need for further research into non-animal methods for studying depression, antidepressants and other areas of research where the forced swim test is currently used
• and, when the forced swim test is used, optimum refinements to maximise animal welfare.

Main report findings

The report highlighted that there are 18 project licences in the UK that authorize the use of the Forced Swim Test. The review of 18 licences was supplemented by the results of two surveys with project licence holders and wider stakeholders.

There was no evidence of mice or rats drowning during or after the forced swim test in the UK and no animals were swum to exhaustion.

The ASC report supports the use of forced swim test for studying the neurobiology of stress, which is what the test is used for at Bristol. The ASC report also supports the use of the forced swim test for the screening of potential antidepressants but advises it is not justified as a model of depression or to study anxiety, but Bristol does not use forced swimming in any of these contexts.

The ASC did not find any evidence of reliable, reproducible and accepted non-animal alternatives to address the purposes for which the use of the forced swim test may be justifiable. Until such replacements are available, ASC has made a series of recommendations to ensure that future use of the forced swim test will be robustly justified and scrutinised.

University review

The University's Animal Welfare and Ethics Review Body (AWERB) convened a meeting to review the ASC report and its relevance to the way the forced swim test is conducted at the University of Bristol. The aim was to seek assurance that the use of the forced swim test at the University is fully justified and using the most refined methods as well as identifying if there were any improvements needed in line with the report's recommendations.

The AWERB was assured that the use of the forced swim test to study the neurobiology of stress was appropriate and that there is not a more refined in vivo method that would deliver the scientific outcome required. It is worth highlighting that the ASC did not identify an alternative method that was more refined.

The AWERB was also assured that other recommendations in the report were considered and used appropriately in the work conducted at Bristol.

Evidence was provided regarding the choice of water temperature (25°C) and the swim times, which are typically six minutes which is less than the maximum reported for rats in the ASC report.

An explanation of how the numbers of animals required in an experiment are calculated was presented and included discussing the desired effect size and power. The AWERB was assured that the experiments consider the balance between refinements for individual animals versus reduction of overall animal use.

The AWERB has a local role to be assured that the benefits accrued from the animal research fall within a permissible purpose under the Animals Scientific Procedures Act and to consider the likely value of the data obtained. This work falls under the permissible purpose of basic research. Basic research is research that is designed to build knowledge and understanding around fundamental biological processes that have the potential for future benefit to humans, animals or the environment.

There are similarities between animals and humans that mean many fundamental processes can be studied and have relevance for humans. The AWERB considered the value of the research using the forced swim test at the University of Bristol was in building understanding around physiological processes that contribute to stress disorders in humans. This has the longer-term potential to contribute to the development of new therapeutic interventions for stress disorders in humans over the next 10 to 15 years.