Fearfulness in aviary housed laying hens – Effects of management and potential confounding effects of the Novel Object test

Abstract

Few studies have assessed fearfulness and how it relates to feather condition and management strategies in end-of-lay hens housed in commercial aviaries. As aviary housing for laying hens grows with the phasing out of cages, there is a need to ensure the currently used methods of assessing on-farm flock fearfulness are robust and to avoid confounding effects. The aim of this study was to investigate the relationship between daily management routines and plumage condition and the fearfulness of aviary housed laying hens as assessed by the Novel Object (NO) test. In addition, the study aimed at investigating potential confounding effects when performing the NO test in commercial flocks. Forty-five indoor multitiered aviary-system flocks of laying hens from across Norway were visited at the end of lay (range: 70–76 wk of age). The flocks consisted of either Lohmann LSL (n = 30) or Dekalb White (n = 15) non-beak-trimmed hens. During the visits, flock fearfulness was assessed using the NO test with 4 different objects, plumage condition was assessed using the NorWel method, and information on how the daily inspections were performed (duration and by how many different people) was collected. More hens tended to approach the NO with less damage to the breast feathers and more damage to the tail feathers in the Lohmann flocks but not in the Dekalb flocks (0.05 < P < 0.07). There was no effect of the number of people involved in the daily inspections of the hens (P = 0.56) or the amount of time spent inside the hen house per day (P = 0.80) on the number of hens approaching the NO. There was also no effect of in which corridor the NO test was carried out (wall vs inner corridors; P = 0.27). But there was an effect of the type of objects (P < 0.0001). More hens approached the “virus” NO compared to the three other objects used. The results support previous works showing a relationship between fearfulness and feather pecking and highlight the need for caution regarding hybrid differences. The results also suggest that, when performing the NO test in commercial aviaries, corridor does not have a confounding effect on this test while the type of novel object can be a confounder.