The development and use of a cage-topper to enhance rat welfare

The welfare of rats used in scientific research is an important concern. A number of recent studies have demonstrated that larger and more complex housing provides a welfare benefit to rats over conventional cages. However, there are typically both practical and financial constraints to implementing this. We have developed a cage topper that can be added to a standard rat cage to provide additional space and complexity and that can be built in-house at a low cost. Here, we introduce the design of this cage topper and discuss its utility from the perspective of a researcher, a named animal care and welfare officer (NACWO)/lead technician, and a named veterinary surgeon (NVS). We conclude that while the cage topper is likely to provide a welfare benefit, more research is needed to assess if there are any adverse effects of the cage topper on animal health and biosecurity. At present, the cage topper may be most useful to enhance to welfare of rats who are healthy and would otherwise be housed in non-IVC conventional cages.