Relationship between Range Use and Fearfulness in Free-Range Hens from Different Rearing Enrichments

Simple Summary In Australia, free-range pullets are reared inside, but the adult hens can go outside. This discrepancy between environments might increase the fearful behaviour of adult free-range hens. Enriching the indoor rearing environments might help reduce this fearfulness. Adult hen fearfulness might also be linked with individual variation in range use. In this study, across 16 weeks of indoor rearing, different types of enrichments were provided to 1700 pullets: weekly changing novel objects, custom-designed perching/navigation structures, or no additional enrichments. Adult hens' range use was tracked via radio-frequency identification (RFID) systems. A sample of hens (n = 135) across all rearing enrichment groups that ranged daily or did not range at all were selected, and several behavioural tests were performed at 62 weeks of age. Overall, the rearing treatments had few effects on the fearfulness behaviour of hens late in the production cycle, and the outdoor rangers were less fearful. Hens that showed higher fear also had poorer feather coverage. Enrichments during rearing showed limited fearfulness reduction for adult free-range hens, and individual variations in range use might be an indicator of bird fearfulness. Inconsistency between the environments of indoor pullet rearing and adult outdoor housing may increase the fearfulness in free-range hens. Rearing enrichments and/or range use may reduce adult fearfulness. Hy-Line Brown(R) chicks (n = 1700) were reared inside across 16 weeks with three enrichment treatments: weekly changing novel objects, custom-designed perching/navigation structures, or no additional enrichments. Pullets were transferred to a free-range system at 16 weeks of age, with range access provided from 25 weeks. At 62 weeks, 135 hens were selected from the three rearing treatments and two ranging groups (indoor: no ranging and outdoor: daily ranging) based on individual radio-frequency identification tracking. Individual behavioural tests of tonic immobility, emergence, open field, and novel object (pen level) were carried out on hens. Spectrograms of vocalisations were analysed for the open field test, as well as computer vision tracking of hen locomotion. The results showed few effects of rearing treatments, with outdoor rangers less fearful than indoor hens. The latency to step in the open field test negatively correlated with hen feather coverage. These results show that individual variation in ranging behaviours is present even following rearing enrichment treatments, and subsequent range use might be an indicator of bird fearfulness.

Automated summary

The study showed that enrichments during rearing had limited effects on reducing fearfulness in adult free-range hens, and individual variations in range use might serve as an indicator of bird fearfulness. Inconsistency between the environments of indoor pullet rearing and adult outdoor housing may increase fearfulness in free-range hens.