Animal Housing and Welfare: Effects of Housing Conditions on Body Weight and Cortisol in a Medium-Sized Rodent (Cavia aperea)

Abstract

Rodents are the most abundant experimental nonhuman animals and are commonly studied under standard laboratory housing conditions. As housing conditions affect animals' physiology and behavior, this study investigated the effects of indoor and outdoor housing conditions on body weight and cortisol level of wild cavies, Cavia aperea. The changing housing condition strongly influenced both parameters, which are commonly used as indicators for animal welfare. The transfer from outdoor to indoor enclosures resulted in a body-weight loss of about 8%. In contrast, animals kept indoors showed a substantial weight gain of about 12% when they were transferred outdoors. These effects were reversible. To substantiate a connection between body-weight changes and the health states of the animals, blood basal cortisol concentrations were measured. Animals kept outdoors had significantly lower cortisol levels than did animals kept indoors. These results imply that indoor conditions have a direct effect on the animals' states. The physiological and metabolic consequences as well as potential welfare aspects should be taken into account when planning experimental work, especially on nondomestic animals.

Keywords::

• housing condition
• wild guinea pig
• indoor keeping
• outdoor keeping
• environmental stimuli

ACKNOWLEDGMENTS

I (K.S.) would like to thank my colleagues from the Department of Behavioural Biology at the University of Bielefeld for their suggestions and support, and especially for the possibility to realize this study on their wild guinea pigs. Additionally, all authors would like to thank Sylvia Kaiser and the laboratory team Münster for running the cortisol analysis.