Associations between welfare indicators and environmental choice in laying hens

• Published in: Animal behaviour 2009-08, Vol.78 (2), p.413-424
• Main Authors: Nicol, Christine J., Caplen, Gina, Edgar, Joanne, Browne, William J.
• Format: Article
• Language: English
• Subjects: Animal behavior; Animal cognition; Animal ethology; animal welfare; Aves; Biological and medical sciences; choice decision making; Correlation analysis; Fundamental and applied biological sciences. Psychology; Gallus gallus; laying hen; Poultry; Psychology. Psychoanalysis. Psychiatry; stress; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; welfare indicator
• ISSN: 0003-3472; 1095-8282
• DOI: 10.1016/j.anbehav.2009.05.016

Animal welfare is usually assessed by measuring animals' responses to different environments or procedures. The alternative approach examines animal decision making, assuming that even domestic animals in artificial environments are able to integrate all relevant inputs and select in their own best interests. These two approaches to animal welfare assessment have been pursued largely in isolation over the past 30 years. If choice is taken as a particularly meaningful welfare measure, then valid behavioural, physiological or physical responses should be statistically associated with choice. We investigated this for the first time. We housed 60 hens, Gallus gallus, sequentially in three environments, experienced as three sets (A versus B; B versus C; A versus C), over a 40-week period. During each set, over 100 responses were recorded for each hen, and choices between all environmental pairs measured. Different types of birds had different environmental preferences. To analyse the relationship between choice and environmental response, we calculated the difference between the response value for each pair of environments. We then used a hierarchical statistical model that controlled for bird, group and order effects. Responses associated with positive choice included lower body temperature, blood glucose, heterophil:lymphocyte ratio and response to novelty, and greater feed digestibility and self-grooming. Conversely, many indicators believed to be valid measures of welfare were not associated with environmental choice. Because the analysis adjusted for preference for specific environments, the indicators identified were associated with general positive or negative choice, providing a platform for further testing.