Environmental Enrichment: Room for Reduction?

Environmental enrichment strategies are usually regarded as refinement. However, when the welfare of animals is enhanced through successful enrichment programmes, a reduction in the number of animals needed can be expected, because fewer animals might be lost during the course of experiments. Several examples of studies where enrichment can lead to reduction will be presented. They include the beneficial effects of nesting material for laboratory mice, the effects of husbandry procedures on controlling aggressive behaviour in male laboratory mice, and the effects of enrichment on variation in the results of experiments.

Effects of environmental enrichment for mice: variation in experimental results

This study focused on the effects of different enriched environments for mice in a number of behavioral and physiological parameters in 2 routine laboratory testing procedures: potency testing for tetanus vaccine and stress-induced hyperthermia. The variability in the results was studied by calculating and analyzing mean absolute devi-ations. Mice from enriched conditions weighed more and consumed more food than mice from standard housing conditions. However, mice from enriched conditions lost more body weight after being housed individually. Other physiological parameters showed no differences. Mice from standard conditions were more active in an open field, suggesting a tendency to overrespond to various stimuli in a testing environ-ment. Mice from enriched environments were more tranquil and easier to handle. The enrichment did not influence the variability in any of the parameters measured, al-though earlier results and results of other studies suggest that the effects on the vari-ability in results are parameter dependent. When enrichment does not influence vari-ability, there is no reason for not introducing cage enrichment and by doing so contributing to the animals' welfare.