Curiosity, fearfulness and use of aviary space in commercial free-range hens

Abstract

Fearfulness and exploration have been associated with the time that free-range hens spend on the range. Further understanding of these traits and the use of distinct areas within a shed may help to improve facility design and management techniques to benefit poultry welfare. The aim of this study was to assess the relationship of fear, exploration and use of key specific resources by individual laying hens on a commercial free-range housing system. The upper and lower chain feeders and the nest box areas in a 3-tier aviary system were monitored in 3 Lohmann Brown flocks from 18-72 weeks of age using a custom-built Radio Frequency Identification system. At 72 weeks of age, 769 hens were selected and subjected to a novel arena test (NA) and novel object test (NO). For NA test, hens were placed into the centre of a square arena (1.7m²) and left for 8 min. Immediately after, a NO was introduced through a small door and left with the hen for 5 min. Hen behaviour was continuously recorded using an overhead video camera and later analysed by ANYmaze tracking software and one observer blinded to treatment. Latency to step, number of lines crossed and escape attempts were assessed as indicators of fear during the NA test. Time spent within three zones (avoidance, approach and interaction) and the number of escape attempts were assessed as indicators of neophobia and exploration during the NO test. Statistical analysis was carried out using a machine learning approach (random forest). The model used 13 features to generate the most important variables for predicting the time spent at each location followed by GLIMM analysis to determine the significant association between factors. Time spent on the upper feeder was associated with less time spent in the NO interaction zone (F_(1,758)=6.26, P=0.013) and less lines crossed in NA test (F_(1,758)=12.1, P=0.001). Time spent at the lower feeder was associated with more time spent in the NO interaction zone (F_(1,750)=8.71, P=0.003), more lines crossed (F_(1,750)=7.35, P=0.007) and vocalisation (F_(1,750)=14.3, P=0.001) during NA test. These results indicate that hens that spent more time on the upper feeder were not curious while the lower feeder tier were more curious as indicated by the approach to novel stimuli. Hens may occupy key specific resources in the shed depending on their temperament. Further studies are warranted to determine if those areas promote exploration and positive welfare state or serve as a refuge.