Cages and IVCs

To reduce fighting among rat populations, the Rowett Institute of Nutrition and Health created special playrooms.

The Rowett Institute of Nutrition and Health at the University of Aberdeen in Aberdeen, Scotland, has a closed colony of Rowett Hooded Listers, which is maintained to produce out-bred rats for experimental studies. The colony consists of 15 male and 60 female breeders. Mating occurs on a fortnightly basis. The female breeders are split into four groups and are used in rotation. Each fortnight there are 15 males and 15 females mating up. When not being used for mating, the males are housed in groups of three and the females in groups of five. For mating, one male is housed with one female for one week. When returned to their home cages the males normally start fighting, which often ends with rats having bite wounds. On occasion these are severe enough that animals need to be either treated or euthanised. An example will illustrate the problem: two groups of three males were observed after being returned to their home cages. Fighting lasted for about ten minutes and involved behaviours such as rearing up, teeth chattering, biting, rolling each other, hiding from each other, and being submissive. All rats had bite wounds and one did not put any weight on its left front leg. This animal was treated with pain relievers and recovered well within 48 hours.

To stop this fighting, it was suggested to give the male rats a transition period together in a large space with extensive environmental challenges and stimulation prior to being returned into their home cages. This resulted in the development of a playroom for rats. The playroom consists of 1-2 racks, cage bottoms and lids, grid floors, cotton cage bonnets, red tunnels, shredded paper and sawdust to produce deep bedding, stock pellets, water bowls, plastic sacks, and plastic balls. All equipment, except for the balls, was readily available and assembled in a way that it could easily be dismantled for cleaning. The playroom provides space as well as the opportunity for the rats to increase behaviour choices and to express appropriate speciesspecific behaviours such as foraging, climbing, and exploring.

An observation sheet was developed to record behaviour of the rats whilst in the playroom and upon return to their home cages.