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Research article - Peer-reviewed, 2005

Housing-related activity in rats: effects on body weight, urinary corticosterone levels, muscle properties and performance

Spangenberg, Elin; Augustsson, Hanna; Dahlborn, Kristina; Essén-Gustavsson, Birgitta; Cvek, Katarina


The cage systems commonly used for housing laboratory rats often results in sedentary and overweight animals, as a consequence of restricted opportunities for physical activity combined with ad libitum feeding. This can have implications both for animal well-being and the experimental outcome. Physical activity has several known positive effects on health and life span, and physical fitness might therefore be incorporated into the animal welfare concept. The aim of this study was to investigate if and how pen housing affects the physical activity and fitness of rats. Thirty-two juvenile male Sprague Dawley rats were randomly assigned to two different housing systems for a 4-week period. Sixteen rats were kept individually in standard Makrolon type III cages (42x26x18 cm) furnished with black plastic tubes (singly housed, SI). The remaining rats were kept in groups of eight, housed in large floor pens (150x210 cm), which were furnished with various objects to increase environmental complexity (pen-housed, PH). The body weight gain, and food and water intake of the rats were measured. During week 3 or 4, home cage behaviour, urinary cortiosterone/creatinine ratios (CO/CR), and muscle strength on an inclined plane, were measured. Enzyme activities and glycogen content were measured in tissue samples from m. Triceps brachii taken after euthanisation at the end of the study. There were no significant differences between groups for food and water intake, but PH-rats weighed 14 % less than SI-rats after four weeks, and PH-rats also had a more diverse behavioural pattern compared to SI-rats. PH-rats had significantly higher oxidative capacity (28% more citrate synthase) and greater glycogen content (28%) in their muscle samples than SI-rats. The PH-rats performed significantly better on the inclined plane, both in the muscle strength test (mean angle 75  0.5 for PH-rats and 69  0.4 for SI-rats) and the endurance strength test (mean time 233  22 s for PH-rats and 73  14 s for SI-rats). There was a negative correlation between body weight and results on the inclined plane for the PH-rats. There were no significant differences between housing types for CO/CR ratio. In conclusion, the large pen represents an environment that stimulates physical activity and a more varied behaviour, which should be beneficial for the welfare of the animal


laboratory animals; housing; physical activity; enrichment; muscle enzyem activity; glycogen; welfare

Published in

Laboratory Animals
2005, Volume: 2005: 39, pages: 45-57