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Conference abstract2008

The use of a laddermill to evaluate the effect of environmental enrichment on physical fitness in laboratory rats

Cvek Katarina, Spangenberg Elin, Dahlborn Kristina

Abstract

The design of cages for laboratory rats has to facilitate their behavioural needs, but this is compromised by the need for cost effectiveness and practicality. Rats are naturally active animals. They have to be housed in cages large enough to be able to both perform risk assessment and increase their physical activity. Therefore, new cage types need to be evaluated in regards to the animals´ behaviour repertoire and physical activity/physical fitness to ensure improved animal welfare. To evaluate the effects of housing on physical fitness we have previously developed a standardized exercise test on the treadmill. However, a combination of the natural sprint like running pattern of rats and the poor design of the treadmill, made it very difficult to make the rats run on the treadmill. The short lanes of the treadmill does not allow sprints and the rats are forced to run in an unnatural manner. A previous study has shown that rats unwilling to run on a treadmill could quite easily be made to climb a laddermill.We have now rebuilt the treadmill to a laddermill. The aim of this study was to investigate whether a standardized exercise (climbing) test on the laddermill could be a useful tool for evaluating the effect of cage types/environmental enrichment on physical fitness. Rats were kept 4 weeks in pairs in standard Makrolon® IV cages or in a group of six in a large (50 x 50 x 50 cm) furnished cage with mesh walls that allows climbing. The rats were acclimatized to the laddermill two minutes twice a week. All rats except one were easily made to climb the laddermill, only by touching or blowing air on their tails. An exercise test was performed by letting the rats climb at intensities 7, 9 and 11 m/min at an inclination of 50°, one minute per intensity. Blood samples were collected before starting the test and after each intensity. Endurance on the laddermill was tested by letting the rats climb at speed 11m/min until exhaustion (defined as refusal to continue to climb despite three air blows). Rats from the large cage had better endurance, lower blood lactate levels and gained less weight than the rats in standard cages. The results from this study show that a standardized exercise test on the laddermill is a useful tool for evaluating the effect of cage types/environmental enrichment on physical fitness in laboratory rats

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