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.

Background: Pain in horses is an emergent welfare concern, and its assessment represents a challenge for equine clinicians. This study aimed at improving pain assessment in horses through a convergent validation of existing tools: we investigated whether an effective analgesic treatment influences the horse grimace scale (HGS) and the concentration of specific circulating microRNAs (miRNAs). Methods: Eleven stallions underwent routine surgical castration under general anaesthesia. They were divided into two analgesic treatment groups: castration with the administration of preoperative flunixin and castration with preoperative flunixin plus a local injection of mepivacaine into the spermatic cords. HGS and levels of seven circulating miRNAs were evaluated pre‐, 8 and 20 hours post‐procedure. Results: Compared to pre‐castration, HGS, miR‐126‐5p, miR‐145 and miR‐let7e increased significantly in horses receiving flunixin at 8 hours post‐castration (Friedman test, p < 0.05). Both behavioural and molecular changes occurred in horses receiving flunixin only, confirming that the addition of local mepivacaine is an effective analgesic treatment. Conclusions: Combining the use of HGS and circulating miRNAs, particularly miR‐145, could be meaningful to monitor acute pain conditions in horses. Our results further validate the HGS as a method to assess acute pain in horses and point out miR‐145 as a promising biomarker to identify pain.

Reasons for performing study: Lack of ‘gold standard’ for pain assessment in horses. Objectives: To assess different approaches of quantifying pain in horses. Castration was chosen as a pain model because of its wide clinical relevance. Study design: Exploratory study. Methods: 51 equine stallions undergoing castration under general anaesthesia were divided in 3 pain‐relieving treatment groups: A) single perioperative administration of flunixin (n = 19), B) additional subsequent flunixin administrations (n = 21), D) like A but with intra‐operative mepivacaine injections into the spermatic cord (n = 11). All horses were assessed before and 5 times after surgery (up to 44 h) by means of a modified composite pain scale ( CPS ), a newly developed facial expression pain scale ( FEPS ), faecal glucocorticoid metabolites ( GCMs ) and plasma cytokine profiles. The same parameters were measured in a control group C , undergoing general anaesthesia for different nonpainful procedures (n = 6). Data were analysed with nonparametric statistical tests (Wilcoxon, Mann Whitney U ). Results: Time had an influence on CPS and FEPS scores in treatment groups A , B and D but not in C . Scores of groups A and B were higher compared to groups D and C at 4 ( CPS , FEPS ) and 8 h ( CPS ), whereas there was no difference between groups A and B nor between groups D and C . Only in group AB was there an increase of faecal GCMs 20 h after surgery. GCMs in group AB were higher compared with groups C and D at 32 h. No effects by time or treatment could be identified for the different plasma cytokines. Conclusions: CPS and FEPS seem to be able to detect different levels of post castration pain differentiating from possible anaesthesia effect. Additional local anaesthesia of the spermatic cord was associated with lower post surgical pain scores when compared to perioperative flunixin application alone, whereas subsequent applications of flunixin had no obvious effect. Ethical animal research: This study was registered as an animal experiment by the Brandenburg state authority ( V 3‐2347‐ A ‐42‐1‐2012). Client‐owned horses were included with informed consent. Sources of funding: EU ‐funded FP 7‐project “Animal Welfare Indicators ( AWIN )” ( FP 7‐ KBBE ‐2010‐4). Competing interests: None.

"Assessment of different methods to identify pain in horses" published on 01 Nov 2014 by Wageningen Academic.