Pain in domestic animals and how to assess it: a review

In recent years more attention has been paid to the issue of pain in animals, particularly in association with increasing awareness of animal welfare. It is therefore necessary for veterinarians to be able recognise unambiguously whether an animal suffers from pain. Adult humans suffering from pain can more or less characterise their painful experiences, including the site and intensity of the pain. However, pain in animals is in some aspects more complex and it can be rather difficult to evaluate the seriousness and impact of painful events. Therefore, in animals we have to recognise the signs of pain according to indirect markers which involve behavioural, physiological and finally clinical responses. Moreover, in particular the behavioural changes associated with pain can be along with the general signs also species-specific, and hardly recognisable (and for an inexperienced observer seemingly unimportant) which makes pain assessment even more complicated. Therefore, the current review formulates definitions of pain, its classification and is focused on methods that may facilitate pain recognition in animals, which is crucial for an effective pain assessment and consequent effective pain management. The review combines recent knowledge with well proven facts concerning pain and furthermore also highlights the author's own research on pain assessment.