Effects of regular handling and exposure to an outside area on subsequent fearfulness and dispersal in domestic hens

Abstract

The effects of regular handling and/or exposure to the outside environment on immature laying hens' ( Gallus gallus domesticus) fear levels and subsequent readiness to disperse in an outdoor area were investigated. When they were between 12 and 20 weeks old, 56 birds were subjected to one of three treatments: (1) no handling plus no outdoor experience (control); (2) regular handling, no outdoor experience; (3) regular handling plus outdoor experience. Fear levels in birds from all three treatments were measured by tonic immobility “righting times” (Experiment 1). Compared with controls, there was a non-significant tendency ( P < 0.1) for regular exposure to an outdoor area to reduce fear levels to a greater degree than regular handling alone. The same subjects were subsequently tested for their readiness to emerge from a familiar box and disperse in an outdoor paddock (Experiment 2). The paddock was divided into three areas: inside the box, within 2 m of the box, and more than 2 m from the box. Birds which had previous experience of the outside environment emerged significantly earlier (and spent less time inside the box) than birds from the other two treatments. Furthermore, these birds were most often seen in the area furthest from the box. There were no significant differences between controls and regularly handled only birds either in emergence time or in the amount of time spent in each area. A third study examined whether the observed relationship between increased outdoor experience and lower fear level applied to adult birds in a large-scale free-range system (Experiment 3). Predominantly “outside” birds (which spent more than half their time outside) had shorter tonic immobility righting times than birds which were never seen outside. The results suggest that regular exposure to an outdoor area (which was more complex and varied than their home pen) during the rearing process increased birds' readiness to utilise the available outdoor area as adults. Such experience also reduced birds' fear levels (in both immature birds and adults), whereas regular handling alone had little or no effect on either measure.