Play stimulation as a possible means to buffer early stress from commercial hatchery treatment in laying hen chicks

Abstract

In commercial hatcheries, laying hen chicks are exposed to a range of stressors that have previously been shown to induce long-term negative effects on their welfare. It has been suggested that stimulation of play behaviour, a self-rewarding activity associated with positive emotions, may be a way to improve animal welfare. We have previously found that chicks play extensively during their first weeks of life if offered the possibility. Our hypothesis was therefore that stimulating play in chicks could buffer the long-term consequences of stress from commercial hatchery routines. Sixty female Lohmann LSL chicks were hatched at a commercial hatchery and transported for four hours before being randomly allocated to two different treatments. Play-stimulated chicks (PC) were taken out of the home pens and introduced in groups of five into a spacious, object-enriched play arena 3×30 min per week for five weeks starting from 9 days of age. Control chicks (CC) were taken out of the home pens at the same time as PC and placed in cardboard boxes for the same amount of time as PC were allowed to play. Between 46 and 57 days of age,behavioural and corticosterone reactivity tests were conducted. There were no differences between the treatment groups in open field activity, but in a novel object test PC were more active and interacted more with the novel object, indicating reduced fear. There were no differences between the treatment groups in duration of tonic immobility or in corticosterone reaction to a brief restraint. Contrary to our predictions, PC showed a more negative bias compared to CC in a cognitive judgement bias test. In conclusion, play stimulation may reduce fearfulness in early-stressed chickens, but the reason for the opposite reaction in the cognitive judgement bias needs further investigation.