Module 03 - The Three Rs of Humane Animal Experimentation

Satisfying the Reduction Principle

Literature searches are vital in preventing unnecessary duplication of experiments. Some duplication of studies is required to ensure that the results from one study are reproducible by other investigators in different laboratories. However, it is not necessary to repeat studies over and over again.

There are several ways in which an investigator may attempt to reduce the number of animals required in a study. It is important to ensure that appropriate numbers of animals are used, both the experimental animals and the controls. This means that the statistical design of the study should be carefully evaluated before the study starts. Perhaps a statistician should be consulted. Good experimental design with proper data collection and analysis will minimize the number of animals required.

A well trained research team extending from the principal investigator to the animal care technicians will ensure that all procedures related to and peripheral to the study will be standardized. It is important that the team members are trained in their specialty and additional expertise brought on as needed. For example, if the project requires a particular surgical procedure for which no one has been trained, an experienced surgeon should assist. Training in all procedures applied to the animals should be done before the project starts.

For teaching laboratories using animals, the success of the laboratory session is greatly increased if trained instructors rather than untrained students set up the animal preparations.

One cause of large group sizes comes from the variability that can occur when the conditions of the experiments are poorly controlled. Large group sizes may be reduced if, for example, a genetically homogeneous population of animals is used, or the animals are not subject to intercurrent diseases, or the husbandry conditions are stable. The issue of variability is considered in more detail in Module#4 Research Issues. In that module, the influence of various parameters (e.g., sound, light, infections, procedures, etc.) on the precision of experimental results is discussed.

Control animals may represent up to 50% of the animals in a study. The investigator should try to minimize the number of control animals. Using one control group with several test groups rather than one control group for each test group may do this. If a particular procedure is used repeatedly in a laboratory, there will be a historical record of controls for that procedure. For a study using the procedure, it may be possible to use a very small number of controls and show that they fall within the historical limits of the controls, rather than use a full complement of controls.

Targeted animal models. In the past, it was difficult to find animal models that accurately mimicked human conditions like many cancers. There were animal models of breast cancer but the cause and the biological behaviour of the cancer differed from that in the human. Thus treatments for the animal model were not necessarily applicable to humans.

The alternative. The development of immune compromised animals meant that cells of human origin could be grown in animals without the need for immune suppression of the host. Now the behaviour and treatment of the tumour in the animal model could reflect the situation in the human. Such precisely targeted animal models will result in an overall reduction in animal use through a reduction in the variability of the model and the increased usefulness of the results.

Genetically modified (GM) animals (transgenic, knockout and mutant) represent alternatives that promise to provide more relevant results for human disease understanding. Initially there may be little reduction or replacement because the production of foundation stocks of GM animals still requires large numbers for breeding. The refinement of results from the GM animals should lead to a more rapid advance in the understanding and treatment of human diseases with the use of smaller numbers of animals.