Environmental factors as hidden variables

K. Dahlborn, Å. Eriksson, I. Lind & L. Lindberg*
Department of Animal Physiology, Swedish University of Agricultural Sciences; *National Veterinary Institute, Uppsala, Sweden

In the 'Directive for the protection of vertabrate animals used for experimental and other scientific purposes (86/609/EEC)' it is stated that: all experimantal animals shall be provided with housing, an environment, at least some freedom of movement, food, water and care which are appropriate to their health and well-being. Animal well-being can be defined as living in physical and psychological harmony with the environment but it is not easy to evaluate animal well-being. Physical factors e.g. light, temperature, humidity are possible to measure and huge efforts have been done during the last decades to standardize the physical environment as well as the health status of laboratory animals. However, many other factors of a more psychological character will also interfere with the animal situation like social interaction between animals, single or group housing and environmental enrichment. In addition, social interaction between man and animal is of importance and the way the animal is trained and handled before, during and after the experimental situation will affect the results. To evaluate well-being a combination of behavioural and physiological variables are therefore used. To exemplify, single housed mice and rats are heavier compared to group housed animals of the same breed and age. Animals from an enriched environment seem to be more active than animals kept under standard conditions in most studies reported. In conclusion: Environmental factors, both physical and psychological, can lead to alterations in the animalīs physiology and thereby change the basal experimental data.
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