Development of the Horse Grimace Scale (HGS) as a Pain Assessment Tool in Horses Undergoing Routine Castration
Emanuela Dalla Costa1*, Michela Minero1, Dirk Lebelt2, Diana Stucke2, Elisabetta Canali1, Matthew C. Leach3
1 Universita` degli Studi di Milano, Dipartimento di Scienze Veterinarie e Sanita` Pubblica, Milan, Italy, 2 Pferdeklinik Havelland / Havelland Equine Hospital, Beetzsee- Brielow, Germany, 3 Newcastle University, School of Agriculture, Food & Rural Development, Newcastle upon Tyne, United Kingdom
Background: The assessment of pain is critical for the welfare of horses, in particular when pain is induced by common management procedures such as castration. Existing pain assessment methods have several limitations, which reduce the applicability in everyday life. Assessment of facial expression changes, as a novel means of pain scoring, may offer numerous advantages and overcome some of these limitations. The objective of this study was to develop and validate a standardised pain scale based on facial expressions in horses (Horse Grimace Scale [HGS]).
Methodology/Principal Findings: Forty stallions were assigned to one of two treatments and all animals underwent routine surgical castration under general anaesthesia. Group A (n = 19) received a single injection of Flunixin immediately before anaesthesia. Group B (n = 21) received Flunixin immediately before anaesthesia and then again, as an oral administration, six hours after the surgery. In addition, six horses were used as anaesthesia controls (C). These animals underwent non-invasive, indolent procedures, received the same treatment as group A, but did not undergo surgical procedures that could be accompanied with surgical pain. Changes in behaviour, composite pain scale (CPS) scores and horse grimace scale (HGS) scores were assessed before and 8-hours post-procedure. Only horses undergoing castration (Groups A and B) showed significantly greater HGS and CPS scores at 8-hours post compared to pre operatively. Further, maintenance behaviours such as explorative behaviour and alertness were also reduced. No difference was observed between the two analgesic treatment groups.
Conclusions: The Horse Grimace Scale potentially offers an effective and reliable method of assessing pain following routine castration in horses. However, auxiliary studies are required to evaluate different painful conditions and analgesic schedules.
Citation: Dalla Costa E, Minero M, Lebelt D, Stucke D, Canali E, et al. (2014) Development of the Horse Grimace Scale (HGS) as a Pain Assessment Tool in Horses Undergoing Routine Castration. PLoS ONE 9(3): e92281. doi:10.1371/journal.pone.0092281
Editor: Edna Hillman, ETH Zurich, Switzerland
Received July 6, 2013; Accepted February 21, 2014; Published March 19, 2014
Copyright: ß 2014 Dalla Costa et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The authors would like to thank the EU VII Framework program (FP7-KBBE-2010-4) for financing the Animal Welfare Indicators (AWIN) project. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist. * E-mail: firstname.lastname@example.org
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