Rewarding memories? Behaviour of broiler chickens towards peat in flocks with and without previous exposure to peat

Abstract

Under commercial conditions, environmental provisions assumed to have an enriching effect on broiler chicken welfare may be offered infrequently and at limited locations, raising questions about their enrichment value. We hypothesized that, if broilers given limited access to peat remembered peat as rewarding, they would subsequently be quicker to exploit fresh peat compared to broilers never previously exposed to peat. We observed 9 control flocks without previous peat exposure and 18 flocks given peat from 1 week of age with variable regularity and in limited locations. During flock visits at approximately 4 weeks of age, we placed 10 L of fresh peat in one location (peat patch) and pretended to do so in another location (control patch, wood shavings litter only). From 20-min video recordings of the peat and control patches, we determined the mean latency for the first five birds to perform standing, lying, ground pecking, ground scratching and vertical wing shaking in each patch. We also recorded the total number of birds present, and proportion lying, per patch based on instantaneous scan sampling at 1-min intervals. We used linear mixed models to assess effects of previous flock exposure to peat, patch type and their interaction, with farm as a random factor. Birds were quicker to ground peck, and slower to stand and lie, in peat than control patches, and the proportion lying was lower (i.e. birds were more active) in peat patches. Birds in peat-exposed flocks were quicker to ground peck than birds without prior peat experience. They also had shorter latencies to stand on peat, and to commence ground scratching and vertical wing shaking in peat, compared to birds in peat-unexposed flocks whereas previous peat exposure did not affect these behaviours in the control patch. In peat-unexposed flocks, birds were slower to stand, in the peat patch than the control patch, and fewer birds were present in the peat patch than the control patch throughout the 20-min observation period. Thus, birds in the peat-exposed flocks were quicker to exploit fresh peat by performing behavioural elements of foraging and dustbathing whereas birds in peat-unexposed flocks showed more caution towards the peat. We conclude that, even though provisioning of peat was relatively sparse and ephemeral, it was sufficient to generate long-term positive memories of the resource and to activate the performance of natural behaviours, supporting its value as an enrichment for broilers under commercial conditions.