Examining the usefulness of a Y-maze choice method to measure the preferences of laying hens

Abstract

Measurement of animal preferences can be used as an indirect, but persuasive, method for assessing animal welfare on the basis that preferences may identify resources and behaviours that might be important to animals. The present experiment examined the usefulness of a Y-maze methodology, incorporating alteration of motivational state through prior restriction of resources of potentially differing value in assessing and understanding animal preferences. The choice behaviour of laying hens for feed, a dustbath substrate (sawdust; ‘dust’) and social contact was measured under three pairwise comparisons in a Y-maze apparatus. In each of the three experiments, 48 birds (HyLine Brown Strain; n = 24 per experiment) were offered a choice of two resources in a Y-maze test, with one of the three possible resource pairings. In each experiment, after Y-maze training, an equal number of birds was deprived in a factorial design of Resource 1, Resource 2, both, or neither resource. Analysis of choices over 24 trials per bird in each experiment revealed that birds preferred feed over social contact or dust, irrespective of restriction of any of these resources, and further, were quicker (P < 0.01) to make feed choices than dust or social-contact choices. In the social contact and dust comparison, restriction of dust significantly (P < 0.05) increased choice for dust in the 24 trials (38 vs 53% dust choice), suggesting that dust restriction increased the birds’ motivation to access dust. This result potentially highlights the impact of the resource of comparison in pairwise tests on overall choice response to restriction. The inclusion of measurements of speed of movement through the Y maze proved a useful aspect of the methodology, providing results consistent with choice behaviour in all three experiments. Although overall choices for dust and social contact were not significantly (P = 0.328) different from random, birds were quicker (P < 0.05) to make dust choices than social-contact choices, suggesting that speed of choice may be a particularly sensitive correlate of current motivation levels. The consistency of results across these experiments, together with results reported in the literature on laying-hen preferences, suggests that the methodology is a promising option for assessing the relative preference for resources for laying hens. Additional evidence, particularly on the occurrence of abnormal behaviour, stress physiology and health, when restricted of the resource of interest is necessary to provide a more comprehensive assessment of the impact of the restriction on animal welfare.