The Push-Door for Measuring Motivation in Hens: Laying Hens are Motivated to Perch at Night
Free-living hens perch on branches in trees and domestic hens (Gallus gallus domesticus) show signs of unrest if they cannot reach a perch, suggesting that night-time perching is a behaviour that hens are motivated to perform. This motivation was quantified in two experiments using a weighted push-door that hens had to push open in order to gain access to a perch. First, the motivation of individual birds to perch, and second, the effect of a companion bird on perching motivation, were measured. Eight adult laying hens (Lohmann Selected Leghorn) were trained to push through the door at increasing resistances, and the individual capacity of each hen was determined. Hens were then tested once per day, at lights-off, in a test pen where pushing through the push-door gave access to the resource. Two consecutive series of increasing resistances were used in the experiment: 25, 50, 75 and 100 per cent of each bird's maximum capacity. In the first experiment, the resources offered were either a perch (treatment) or a 'sham perch' that could not be used for perching (control). Hens opened significantly heavier doors in order to gain access to a perch than to gain access to the sham perch. In the second experiment, pushing through the door gave access either to a perch with a companion hen already perching on it (treatment) or to a perch and a companion hen roosting on the floor (control). In this comparison, four of the hens did not push through the door, probably because of aggressive interactions with the companion, and no significant differences between treatments were found. We conclude that hens are motivated to use a perch for night-time roosting and that they should be housed in systems with perches.
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