Assessing and Enriching the Cage Environment of Laboratory Rats

Abstract

Public concern with the caging conditions of animals kept in laboratories led to research assessing the standard conditions of rats housed in New Zealand laboratories. A total of 113 rats were used in experiments of four basic types. The experiments presented in the first and second chapters assessed the behaviours of rats housed in enriched, standard and deprived conditions. The assessment procedures used were the emergence box, open field and Hebb William's maze as well as the T-maze and a range of operant procedures. The behaviour of rats housed in standard conditions for the emergence box, open field and maze were intermediate between the enriched and deprived rats, but more closely resembled that of the deprived rats. However, the deprived rats displayed no general cognitive deficits on procedures other than the Hebb William's maze, causing the validity of the maze in this context to be questioned. A more specific cognitive deficit relating to attention at the time of encoding was indicated. The thesis then moved from looking for behavioural damage to examining what conditions rats would prefer, and extending these findings using behavioural economics. The rats showed significant preferences for only a small number of cage modifications. They clearly preferred nesting boxes and shredded paper, and showed some preference for a larger group size of rats. The demand experiments demonstrated that the rats worked hardest for access to moderately sized environments with a group size of six. Therefore, the recommendation arising from the current study is that rats should be provided with nest boxes and paper, and provision should be made in the future for using cages suitable for groups of around six. There were also implications for the range of procedures used during the course of this investigation. The open field data suffers from an unstandardised procedure that probably allows a range of confounding variables to come into effect, specifically changes in activity across time. The preference tests (T-maze and continuous access) gave broadly equivalent data although there were small systematic differences in the results between the two tests which suggest they should be used together in order to cancel out these biases. The demand procedure is the pre-eminent option from a theoretical point of view but the detail of the procedure is in need of some development. The best way to achieve this progress would be through more extensive applied use of behavioural economics.