A review of behavioural and physiological responses of sheep to stressors to identify potential behavioural signs of distress
This paper discusses the potential for using observations of behaviour to recognise distress in sheep. The term distress is used to describe situations in which an animal is likely to be suffering, and is indicating this by overt behavioural signs. Literature on the behavioural responses
of sheep to procedures that induce a physiological stress response is reviewed. This approach is based on human analogy and the assumption that physiological changes can be used to differentiate between stimuli that induce an emotional response in sheep and those that do not. The degree to
which the behaviour of sheep in certain situations represents, at least in part, an expression of emotional behaviour, or whether it can be fully explained as a functional response to a specific situation, is a fundamental and unresolved question in ethological and psychological studies. Therefore,
the validity of compiling a list of objective common behavioural indicators of distress in sheep will be contentious. However, it is important to be able to recognise and deal with suffering, and the use of behavioural methods for the identification of distress in sheep is a practical welfare
issue. There is a need for further research to identify indicators of distress in sheep, but in the meantime it would be reasonable to make the judgement that, in some circumstances, sheep that are found to be vocalising, panting, and/or showing markedly increased locomotory activity could
be experiencing distress.