Environmental enrichment for laboratory rodents and rabbits: requirements of rodents, rabbits, and research.

Environmental conditions such as housing and husbandry have a major impact on the laboratory animal throughout its life and will thereby influence the outcome of animal experiments. However, housing systems for laboratory animals have often been designed on the basis of economic and ergonomic aspects. One possible way to improve the living conditions of laboratory animals is to provide opportunities for the animals to perform a species-specific behavioral repertoire. Environmental enrichment should be regarded both as an essential component of the overall animal care program and equally important as nutrition and veterinary care. The key component of an enrichment program is the animal staff, whose members must be motivated and educated. It is critically important to evaluate environmental enrichment in terms of the benefit to the animal by assessing the use of and preference for a certain enrichment, the effect on behavior and the performance of species-typical behavior, and the effect on physiological parameters. At the same time, it is necessary to evaluate the impact on scientific outcome, how the enrichment influences the scientific study, and whether and how the statistical power is affected. The result will depend on the parameter measured, the type of enrichment used, and the animal strain. In this article, goals of enrichment are defined and discussed. Animal behaviors and needs are described, along with the translation of those needs into environmental enrichment programs. Specific types of environmental enrichment are outlined with examples from the literature, and an evaluation of environmental enrichment is provided.