title: An equine pain face.
abstract: OBJECTIVE
  The objective of this study was to investigate the existence of an equine pain face and to describe this in detail.
  
  
  METHODS
  Semi-randomized, controlled, crossover trial.
  
  
  METHODS
  Six adult horses.
  
  
  METHODS
  Pain was induced with two noxious stimuli, a tourniquet on the antebrachium and topical application of capsaicin. All horses participated in two control trials and received both noxious stimuli twice, once with and once without an observer present. During all sessions their pain state was scored. The horses were filmed and the close-up video recordings of the faces were analysed for alterations in behaviour and facial expressions. Still images from the trials were evaluated for the presence of each of the specific pain face features identified from the video analysis.
  
  
  RESULTS
  Both noxious challenges were effective in producing a pain response resulting in significantly increased pain scores. Alterations in facial expressions were observed in all horses during all noxious stimulations. The number of pain face features present on the still images from the noxious challenges were significantly higher than for the control trial (p = 0.0001). Facial expressions representative for control and pain trials were condensed into explanatory illustrations. During pain sessions with an observer present, the horses increased their contact-seeking behavior.
  
  
  CONCLUSIONS
  An equine pain face comprising 'low' and/or 'asymmetrical' ears, an angled appearance of the eyes, a withdrawn and/or tense stare, mediolaterally dilated nostrils and tension of the lips, chin and certain facial muscles can be recognized in horses during induced acute pain. This description of an equine pain face may be useful for improving tools for pain recognition in horses with mild to moderate pain.
authors.affiliation: Department of Large Animal Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Karina B
authors.initials: KB
authors.lastname: Gleerup
authors.forename: Björn
authors.initials: B
authors.lastname: Forkman
authors.forename: Casper
authors.initials: C
authors.lastname: Lindegaard
authors.forename: Pia H
authors.initials: PH
authors.lastname: Andersen
mesh_terms: D000818:Animals; D018592:Cross-Over Studies; D005149:Facial Expression; D006734:Horse Diseases / Q000175:diagnosis*; D006736:Horses; D010146:Pain / Q000175:diagnosis / Q000662:veterinary*; D010147:Pain Measurement / Q000379:methods / Q000662:veterinary*
keywords: experimental study; horses; pain behavior; pain evaluation; pain face
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