Validating attention bias as a novel measure of affect in sheep

Abstract

To facilitate the understanding and enhancement of animal well-being in livestock production systems, there is a need to develop robust methods which can assess the emotional or affective states of animals, as an aspect of their welfare. Chapter 1 of this thesis discusses some current methods used for the assessment of animal affect, highlighting the key limitations of each approach. The potential role of cognitive methods for welfare assessment is introduced, with a particular focus on attention bias tests. The aim of this thesis was to further develop and validate a novel attention bias test for the assessment of affective states in sheep. Chapter 2 examines the impact of pharmacologically-induced stress on judgement bias and attention bias in sheep. The study finds no clear indication that elevated cortisol concentrations impacted on cognitive biases in sheep. Chapter 3 refines the attention bias test methodology to remove a habituation period, improving the practical application of the test. The study demonstrates that pharmacologically-induced anxiety-like and calm-like states impact on attention bias in sheep. Chapter 4 introduces a modified method for the assessment of attention bias, which is shown to assess and differentiate pharmacologically-induced anxiety-like and depression-like states in sheep. Chapter 5 examines the potential influence of pharmacologically induced positive affective states on the modified attention bias test, finding no clear effect of positive states on attention bias in sheep. It is suggested that external factors may have confounded results of this study. Chapter 6 examines repeatability of the attention bias test to gain insight into the factors influencing animal behaviour during the attention bias test. Key measures of attention had low repeatability and are suggested to be readily influenced by emotions and moods. Measures of vigilance and zones crossed had moderate repeatability and are suggested to be more heavily influenced by temperament or personality traits. Finally, chapter 7 concludes that the attention bias test developed throughout this thesis may be a useful and practical tool for the assessment of negative affective states in sheep