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Consequences of enhancing environmental complexity for laboratory rodents — a review with emphasis on the rat

Published online by Cambridge University Press:  11 January 2023

DB Sørensen ,
JL Ottesen  and
AK Hansen
DB Sørensen*
Affiliation:
Centre for Bioethics and Risk Assessment, Division of Laboratory Animal Science and Welfare, Department of Veterinary Pathobiology, The Royal Veterinary and Agricultural University of Copenhagen, Groennegaardsvej 15, 1870 Frederiksberg C, Denmark
JL Ottesen
Affiliation:
Novo Nordisk A/S, Novo Nordisk Park, 2760 Måløv, Denmark
AK Hansen
Affiliation:
Centre for Bioethics and Risk Assessment, Division of Laboratory Animal Science and Welfare, Department of Veterinary Pathobiology, The Royal Veterinary and Agricultural University of Copenhagen, Groennegaardsvej 15, 1870 Frederiksberg C, Denmark
*
* Contact for correspondence and requests for reprints: [email protected]
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Abstract

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Enhancing the complexity of the environments of captive animals is often referred to as environmental enrichment, and aims to have positive effects on the animals’ well-being. Such enrichments may have consequences both for so-called ‘normal’ behaviour and for the pathophysiology of the animals in question. The effects of a lack of environmental complexity, including social isolation, on home cage behaviour and on pathophysiology in rats is considered in this review. Several preference tests on rats — choice tests and operant tests — indicate a preference for bedding, nesting material and social contact. Contradictory research results concerning the need for gnawing objects per se are more difficult to interpret, and it is argued that excessive gnawing may be indicative of primary frustration and hence reduced welfare. One disadvantage of providing environmental enrichment to laboratory animals is a possible increase in subject variability, resulting in the need to use a greater number of test animals. However, this increased variability seems to be inconsistent and is not very well documented. It is argued that in cases where the behavioural benefits of environmental enrichment justify the use of more animals, better welfare should be more highly valued than a reduction in the number of animals used.

Keywords

animal welfareenvironmental complexityenvironmental enrichmenthousingmicerat
Type
Research Article
Information
Animal Welfare , Volume 13 , Issue 2 , May 2004 , pp. 193 - 204
Copyright
© 2004 Universities Federation for Animal Welfare

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