Night-time roosting in laying hens and the effect of thwarting access to perches

Free-living hens roost on branches in trees at night, and laying hens in aviary systems or cages provided with perches also make extensive use of these for night-time roosting. It is therefore suggested that roosting on perches is important to the hens and that domestic hens should be provided with perches in order to promote welfare. However, no study has addressed the question of motivation for roosting. In the present experiment, we studied undisturbed roosting behaviour and the reaction of commercial laying hens when roosting on perches was thwarted. Fifty-two adult hens (Lohmann Selected Leghorn, LSL) were kept in two groups of 26 hens in litter pens with perches at heights of 23, 43 and 63 cm. Behaviour was observed for 60 min starting at lights-off, registering the number of hens on each perch level. The hens started to get onto the perch immediately and within 10 min after lights-off, more than 90% of the hens were on the perch. All hens roosted close together on the top perch. In a second experiment, 24 hens were kept in eight groups of three birds each in experimental pens equipped with perches. Birds were tested in four different situations: (1) the pen unchanged (Base), (2) the perch covered with plexiglass (PCov), (3) the perch removed (PRem) and (4) the unchanged pen (Post). The order of PCov and PRem alternated between groups in a balanced manner and all groups of birds experienced all four treatments. The hens were observed for 60 min from lights-off using focal sampling. For comparisons, the Post treatment served as the control. In the treatments where perching was not possible, the hens spent less time sitting (p=0.042), and also tended to spend more time standing (p=0.06), than in the control. Furthermore, the hens moved more (p=0.042) when the perch was inaccessible, and when the perch was visible but inaccessible they also showed more attempts to take off (p=0.042). These findings can be interpreted as increased frustration and/or exploration, probably to find an alternative roosting site. Together with the high use of perches for night-time roosting under undisturbed conditions, these results indicate that laying hens are motivated to perch and imply that hens kept under conditions where perching is not possible may experience reduced welfare.