Dirk Lebelt

Development of the Horse Grimace Scale (HGS) as a Pain Assessment Tool in Horses Undergoing Routine Castration

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.

Using the Horse Grimace Scale (HGS) to Assess Pain Associated with Acute Laminitis in Horses (Equus caballus)

Simple Summary Acute laminitis is a common equine disease characterized by intense foot pain. This work aimed to investigate whether the Horse Grimace Scale (HGS), a facial-expression-based pain coding system, can be usefully applied to assess pain associated with acute laminitis in horses at rest. Ten horses, referred as acute laminitis cases with no prior treatment, were assessed at the admission and at seven days after the initial evaluation and treatment. The authors found that the Horse Grimace Scale is a potentially effective method to assess pain associated with acute laminitis in horses at rest, as horses showing high HGS scores also exhibited higher Obel scores, and veterinarians classified them in a more severe painful state. Abstract Acute laminitis is a common equine disease characterized by intense foot pain, both acutely and chronically. The Obel grading system is the most widely accepted method for describing the severity of laminitis by equine practitioners, however this method requires movement (walk and trot) of the horse, causing further intense pain. The recently developed Horse Grimace Scale (HGS), a facial-expression-based pain coding system, may offer a more effective means of assessing the pain associated with acute laminitis. The aims of this study were: to investigate whether HGS can be usefully applied to assess pain associated with acute laminitis in horses at rest, and to examine if scoring HGS using videos produced similar results as those obtained from still images. Ten horses, referred as acute laminitis cases with no prior treatment, were included in the study. Each horse was assessed using the Obel and HGS (from images and videos) scales: at the admission (before any treatment) and at seven days after the initial evaluation and treatment. The results of this study suggest that HGS is a potentially effective method to assess pain associated with acute laminitis in horses at rest, as horses showing high HGS scores also exhibited higher Obel scores and veterinarians classified them in a more severe painful state. Furthermore, the inter-observer reliability of the HGS total score was good for both still images and video evaluation. There was no significant difference in HGS total scores between the still images and videos, suggesting that there is a possibility of applying the HGS in clinical practice, by observing the horse for a short time. However, further validation studies are needed prior to applying the HGS in a clinical setting.

Welfare assessment of horses: the AWIN approach

The EU-funded Animal Welfare Indicators (AWIN) research project (2011–2015) aimed to improve animal welfare through the development of practical on-farm animal welfare assessment protocols. The present study describes the application of the AWIN approach to the development of a welfare assessment protocol for horses (Equus caballus). Its development required the following steps: (i) selection of potential welfare indicators; (ii) bridging gaps in knowledge; (iii) consulting stakeholders; and (iv) testing a prototype protocol on-farm. Compared to existing welfare assessment protocols for other species, the AWIN welfare assessment protocol for horses introduces a number of innovative aspects, such as implementation of a two-level strategy focused on improving on-farm feasibility and the use of electronic tools to achieve standardised data collection and so promote rapid outcomes. Further refinement to the AWIN welfare assessment protocol for horses is needed in order to firstly gather data from a larger reference population and, secondly, enhance the welfare assessment protocol with reference to different horse housing and husbandry conditions.

Do Different Emotional States Affect the Horse Grimace Scale Score? A Pilot Study

Abstract The Horse Grimace Scale (HGS) is a facial‐expression–based pain coding system that incorporates six Facial Action Units, independently scored. The aim of this pilot study was to determine whether HGS score changed in response to emotional states other than pain. Seven riding school horses were exposed to different experimental conditions that are known to elicit different emotional states (new environment, grooming, anticipation of food reward, fear). As a control, videos were also recorded with the horse undisturbed in their home environment. Videos were recorded in each experimental condition and individual frames were captured from HD video files. Thirty‐five pictures were scored using HGS by three experimental design blind observers. The results showed that the HGS score did not change in any of the experimental conditions when compared with control. In all the conditions but one (fear), the mean HGS score was low (≤2 on a maximum score of 12), but not zero; the scores of stiffly backward ears and prominent strained chewing muscles tended to be higher in fear than in other conditions. Although these are preliminary results as the number of tested horses is limited, HGS seems to be a specific tool to assess pain in horses. Changes in ear posture and tension in chewing muscles tend to be present in negative emotional states such as fear; therefore, a larger scale study is needed to collect data from the same horses in positive and negative situations, including pain. HighlightsHGS score did not change in any of the four experimental conditions when compared to control.The mean HGS score was low (≤2 out of 12) in all the conditions but one (fear).The scores of stiffly backwards ears and prominent strained chewing muscles tended to be higher in fear than in other conditions.Although this is a pilot study, the results suggest that HGS could be considered a specific indicator for assessing pain in horses.

Simultaneous detection and quantification of six equine cytokines in plasma using a fluorescent microsphere immunoassay (FMIA).

Cytokines are cell signalling proteins that mediate a number of different physiological responses. They are also biomarkers for inflammatory conditions and potential diagnostic references for diseases. Until recently, simultaneous quantification of cytokine profiles had not been possible. Now however, fluorescent microsphere immunoassays (FMIA) are able to measure multiple cytokines in a single sample. The following pro-inflammatory and anti-inflammatory cytokines were quantified in equine plasma and serum samples: interleukin (IL)-2, IL-4, IL-6, IL-10, interferon (IFN)-γ, tumor necrosis factor (TNF)-α. • The objective of this study was to quantify six equine cytokines simultaneously using the BioPlex® 200 system in equine EDTA-plasma and serum.• It demonstrates an increased number of detectable cytokines over published studies.• This technology has the advantage of reduced sample volume and assay time compared to traditional sandwich ELISAs.

Can grimace scales estimate the pain status in horses and mice? A statistical approach to identify a classifier

Pain recognition is fundamental for safeguarding animal welfare. Facial expressions have been investigated in several species and grimace scales have been developed as pain assessment tool in many species including horses (HGS) and mice (MGS). This study is intended to progress the validation of grimace scales, by proposing a statistical approach to identify a classifier that can estimate the pain status of the animal based on Facial Action Units (FAUs) included in HGS and MGS. To achieve this aim, through a validity study, the relation between FAUs included in HGS and MGS and the real pain condition was investigated. A specific statistical approach (Cumulative Link Mixed Model, Inter-rater reliability, Multiple Correspondence Analysis, Linear Discriminant Analysis and Support Vector Machines) was applied to two datasets. Our results confirm the reliability of both scales and show that individual FAU scores of HGS and MGS are related to the pain state of the animal. Finally, we identified the optimal weights of the FAU scores that can be used to best classify animals in pain with an accuracy greater than 70%. For the first time, this study describes a statistical approach to develop a classifier, based on HGS and MGS, for estimating the pain status of animals. The classifier proposed is the starting point to develop a computer-based image analysis for the automatic recognition of pain in horses and mice.