The effects of gestational and postpartum environmental enrichment on the mother rat: A preliminary investigation

Environmental enrichment is known to influence an animal's well-being, provide opportunities for activity, and encourage behaviours appropriate to the species. Female Long–Evans rats were co-housed during their gestational and postpartum times in a colony housing environment comprising numerous cages, with interconnecting tubes, surrounding a multileveled enclosure with many objects scattered throughout. A control group of rats were housed in standard cages. The effects of the physical and social enrichment were determined by evaluating group differences in body weight, litter characteristics, elevated-plus maze performance during the gestational and postpartum periods, and Morris water maze behaviour (postpartum only). Results showed that enriched females were leaner and maintained a constant postpartum weight. Group differences in litter characteristics were observed, with enriched females having heavier but fewer offspring. Behavioural trends were observed in the elevated-plus maze with enriched rats showing greater change in behaviours over time. In the Morris water maze probe test, enriched rats performed less thigmotaxic and more middle maze swimming, as well as an increased tendency to enter the quadrant where the platform was located in non-probe trials. A housing environment, with complex physical and social stimulation, offered more opportunity for environmental interactions producing heartier pups and leaner mothers that displayed differential behavioural responses compared to control mothers. Studying maternal–offspring interactions in a more naturalistic environment allows one to observe a greater repertoire of behaviours that accommodates adequate normal or natural cognitive development than can be observed in the typical standard housing laboratory condition that limits experience and environmental engagement.