Abstract

This experiment was carried out to investigate the long-term effects of enhancing cage complexity on
behavioural measures of welfare in laboratory rats.Wehoused 72 rats in groups of four in either ‘enriched’
or ‘unenriched’ cages for six weeks. Scan and focal animal sampling were conducted in both the light
and dark phase of the second, fourth and sixth weeks. Results revealed that rats in the ‘enriched’ cages
showed longer durations of sleep behaviour, and low levels of agonistic behaviour compared to rats in
the ‘unenriched’ cages. Results importantly demonstrated that the behavioural changes observed in the
enriched environment were due to the presence of the enrichments themselves in the cages (indirect
effects) and not due merely to rats interacting with the enrichment items in their environment. Thus,
enhancing the complexity of conventional laboratory cages can promote behaviour such as longer bouts
of sleep that is likely to be indicative of good welfare, and diminish levels of behaviour such as aggression
that is likely to lead to poor welfare.