Nesting material as environmental enrichment has no adverse effects on behavior and physiology of laboratory mice

Environmental enrichment may improve the quality of life of captive animals by altering the environment of animals so that they are able to perform more of the behavior that is within the range of the animal's species-specific repertoire. When enrichment is introduced into an animal's environment, it is important to evaluate the effect of the enrichment program and to assess whether the animal continues to use the enrichment in the long-term. Groups of mice were housed under either standard or enriched conditions for several weeks. Nesting material which was highly preferred in previous studies was used as enrichment. During the period of differential housing several behavioral parameters (behavioral tests and handling) and physiological parameters (urine and plasma corticosterone, food and water intake, body and adrenal weight) were monitored to determine the impact of environmental enrichment. Observations were made to determine whether or not the mice continued to use the enrichment. The results indicated that throughout the study all mice used the nesting material to build nests and that mice from enriched conditions weighed more than mice housed under standard conditions, although the latter consumed more food. No major differences for behavioral and physiological parameters were found between the groups of mice housed under different conditions. Therefore it is not likely that supply of nesting material will jeopardize the outcome of experiments.