Pain expression - linked to personality in horses
Pain is a feeling associated with actual or potential tissue damage that alters behaviour to prevent further damage. With animals, welfare assessments rely on physiological and behavioural indicators. However, in previous studies it has been shown that, as humans, animals too show inter-individual differences in pain threshold. Pain can cause stress and coping styles in horses can vary - from showing the slightest pain, to hiding strong pain.
This study aims to show whether personality is associated with level of pain behaviour demonstrated. Neuroticism and Extroversion are the main categories where neurotic horses have a predisposition towards anxiety and increased stress sensitivity, and extroversion presented as adventurousness and excitability.
As pain behaviour, such as lameness, is often used to assess progression of a condition, the efficacy of analgesia, etc. This study first assessed whether lameness could accurately predict the severity of tissue damage. 21 horses of different breeds with pre-existing lameness were used. An experienced equine vet scored horses for lameness (AAEP scale of 0-5), afterwards x-ray or ultrasound was used to check the severity of tissue damage. A questionnaire was filled out to assess the neuroticism and extroversion of the equines.
It was found that Neuroticism links with several aspects of pain behaviour and highly neurotic horses were found to be less stoic. Horses that are more neurotic are likely to be more stressed by pain, they show it at an earlier stage of degeneration and therefore be assessed earlier, preventing further injury. Such individuals might also have greater fear of movement and re-injury. Introverts, however, seem unstressed mainly due to their passive refusal and lack of response to stimuli. It is yet not known what strategies they use as part of their reactive response.
As welfare assessment, veterinary practice and pain research, all use pain behaviour to quantify pain, further research is highly recommended.
> From: Ijichi et al., Appl Anim Behav Sci. 152 (2014) 38-43. All rights reserved to Elsevier B.V.. Click here for the online summary.