Rat housing

The established legal minimum cage dimensions for rats, set out in Annex III to the Directive 2010/63/EU, are such that rats cannot perform many of their natural behaviours. For example, rats cannot run, stand upright, burrow, climb, or build a good quality nest in standard laboratory rat housing systems. The current enclosure dimensions do not provide enough room for complexity, nor do they enable the rats to compartmentalize their home cage. The drive to perform these behaviours is innate in rats, despite decades of breeding in captivity, and a range of studies investigating the preference of rats for bedding, shelter, complexity and segregation of space show the need for more space to accommodate this. This clearly shows that with regard to rat housing, Annex III of the EU Directive seriously falls short of the requirement in Directive Article 33(1)(b) to minimise restrictions on the extent to which animals can satisfy their physiological and ethological needs. This will have a significant negative impact not only on animal welfare, but also on the science. For example, a robust meta-analysis of 240 studies has shown that conventional laboratory housing increases morbidity and mortality in both mice and rats in a range of research fields, raising questions about the validity and generalisability of the data. This Working Group will define improved rat housing standards that can be consistently applied, using a broad evidence base to ensure that these are feasible and will benefit animal welfare, data quality and staff wellbeing.