Assessment of pain and welfare in sheep

Animal welfare is the combination of subjective and objective (qualitative and quantitative) aspects of the conditions of life for animals, including health and disease, behaviour, husbandry and management, and is thus, a complex and abstract construct. Many definitions of farm animal welfare exist, but it is recognized that many prevalent inflammatory diseases are a major contributor to adverse welfare worldwide. Inflammation induces alterations in nociceptive information processing, which may have serious consequences for animals. Allodynia (perception of innocuous stimuli as noxious) and hyperalgesia (exaggerated responses to noxious stimuli) are common features of inflammatory pain. When these changes occur, animals and humans are said to be hyperalgesic, that is they respond to an unpleasant stimulus at a level which would not affect normal individuals. Hyperalgesia can therefore, be used as an indicator of the presence of pain. Subjective and objective measures of pain in sheep have been investigated. Subjective measures include assessment of behaviours and the use of a number of scales to assess severity based on clinical and pathological signs. Objective measures include the use of cortisol, acute phase proteins and hyperalgesia. Sheep with footrot and chronic mastitis, and cows with lameness and acute mastitis, have been shown to be hyperalgesic and studies have shown that use of non-steroidal anti-inflammatory drugs (NSAIDs) may be useful in reducing hyperalgesia. Work is going on to develop composite indices that can be employed to assess both pain and welfare in sheep and other livestock species and that may be employed to measure changes in these parameters over time. (c) 2005 Elsevier B.V. All rights reserved.