Preliminary evaluation of a behaviour-based system for assessment of post-operative pain in horses following arthroscopic surgery

Objective To develop a method for objective assessment of equine post‐operative pain. Study design Prospective nonblinded clinical study. Animals Twelve adult horses: Group 1 (G1, n = 6), admitted for arthroscopy (under general anaesthesia, with multimodal analgesia); Group 2 (G2, n = 6), ‘pain free’ controls. Materials and methods Horses were filmed continuously (CVI, time‐lapse video recorder) over 72 hours, from 24 hours pre‐surgery (PS) to 48 hours post‐recovery (PR) (G1), and over 24 hours (G2). Activity budgets were determined from 24 to 0 hours PS, 0–24 and 24–48 hours PR (G1) and for 24 hours (G2). Using direct observation (DO), active behaviours and postures were recorded at set time points PS and PR (G1) and at two time points (morning/evening) (G2). Heart rate (HR) and respiration rate (RR) were recorded simultaneously. Statistical analysis investigated within‐group and between‐group time‐related changes in behaviour, HR and RR. Results There was no difference in HR or RR between G1 and G2 at any time point. Anaesthetic ‘hangover’ and hunger‐related activity modulated behaviour from 0 to 6 hours PR, when abnormal postures and locomotion occurred in all G1 horses, but no G2 horses. Compared with G1 (0–24 hours PR), G2 spent more time eating (t = ?3.34, p < 0.01), more time at the front of the stable (t = ?2.42, p < 0.05), and less time exhibiting ‘abnormal’ behaviour (U = 56, p < 0.01). Comparing PS and PR behaviour, G1 spent less time exploring from 24 to 48 hours PR (t = 3.49, p < 0.05), less time in sternal recumbency (t = ?3.8, p < 0.05) and less time moving (t = 3.19, p < 0.05). Horses tended (p < 0.07) to spend less time positioned in the front of the stable PR (less from 24 to 48 hours PR than from 0 to 24 hours PR). Comparing PR (evening) behaviour, G2 spent more time with head above withers (U = 21.5, p < 0.01), and ears forwards (U = 22, p < 0.01). G1 showed time‐related changes (all p < 0.05) in time with lower lip tense (S = 15.8), eating (S = 17.08) and with head positioned above withers (S = 18.04). No differences in event behaviours were observed between G1 and G2. Within G1, only olfactory behaviour varied significantly with time (S = 14.52, p < 0.05). Conclusions Changes in equine behaviour suggestive of post‐operative discomfort were identified using both DO and CVI. Analysis of activity budgets may be a more sensitive method of identifying behavioural changes indicative of equine discomfort than repeated DO of specific events and postures.     

Recognition and quantification of pain in horses: A tutorial review

Pain management is dependent on the quality of the pain evaluation. Ideally, pain evaluation is objective, pain‐specific and easily incorporated into a busy equine clinic. This paper reviews the existing knowledge base regarding the identification and quantification of pain in horses. Behavioural indicators of pain in horses in the context of normal equine behaviour, as well as various physiological parameters potentially useful for pain evaluation, are discussed. Areas where knowledge is sparse are identified and a new equine pain scale based on results from all reviewed papers is proposed. Finally, the most important considerations in relation to the implementation of a pain scale in a hospital setting are discussed.     

Behavioural assessment of pain in 66 horses,with and without a bit

Horses can be ridden with or without a bit. Comparing the behaviour of the same horse in different modes constituted a ‘natural experiment’. Sixty-nine behaviours in 66 bitted horses were identified as induced by bit-related pain and recognised as forms of stereotypic behaviour. A prototype questionnaire for the ridden horse was based on 6 years of feedback from riders who had switched from a bitted to a bit-free bridle. From a template of 69 behavioural signs of pain derived from answers to the questionnaire, the number of pain signals shown by each horse, first when bitted and then bit-free, was counted and compared. After mostly multiple years of bit usage, the time horses had been bit-free ranged from 1 to 1095 days (median 35). The number of pain signals exhibited by each horse when bitted ranged from 5 to 51 (median 23); when bit-free from 0 to 16 (median 2). The number of pain signals for the total population when bitted was 1575 and bit-free 208; an 87% reduction. Percentage reduction of each of 69 pain signals when bit-free, ranged from 43 to 100 (median 87). The term ‘bit lameness’ was proposed to describe a syndrome of lameness caused by the bit. Bit pain had a negative effect on proprioception, i.e. balance, posture, coordination and movement. Only one horse showed no reduction in pain signals when bit-free. The welfare of 65 of 66 horses was enhanced by removing the bit; reducing negative emotions (pain) and increasing the potential to experience positive emotions (pleasure). Grading welfare on the Five Domains Model, it was judged that – when bitted – the population exhibited ‘marked to severe welfare compromise and no enhancement’ and – when bit-free – ‘low welfare compromise and mid-level enhancement.’ The bit-free data were consistent with the ‘one-welfare’ criteria of minimising risk and preventing avoidable suffering.     

Perioperative pain management in horses

The inability to talk does not diminish an animal's ability to experience pain, although it may hinder its recognition and therefore lead to the under-treatment of pain. Pain assessment and treatment in horses has advanced considerably with the recent publication of numerous research papers in this area. This review will summarise these research findings and suggest how advances in knowledge of perioperative pain management can be implemented in equine clinical practice.     

Standing low-field magnetic resonance imaging in horses with chronic foot pain

Objective Conventional imaging modalities can diagnose the source of foot pain in most cases, but have limitations in some horses, which can be overcome by using magnetic resonance imaging (MRI). However, there are no reports of the MRI appearance and prevalence of foot lesions of a large series of horses with chronic foot lameness. Methods In the present study, 79 horses with unilateral or bilateral forelimb lameness because of chronic foot pain underwent standing low‐field MRI to make a definitive diagnosis. Results Of the 79 horses, 74 (94%) had alterations in >1 structure in the lame or lamest foot. Navicular bone lesions occurred most frequently (78%) followed by navicular bursitis (57%), deep digital flexor tendonopathies (54%) and collateral desmopathy of the distal interphalangeal joint (39%). Effusion of the distal interphalangeal joint was also a frequent finding (53%). Conclusion Low‐field MRI in a standing patient can detect many lesions of the equine foot associated with chronic lameness without the need for general anaesthesia.     

The pharmacokinetics and antiparasitic activity of ivermectin in Hutsul and Toric horses

The aim of this study was to compare the pharmacokinetics of ivermectin and its antiparasitic activity in two horse breeds. Eight Hutsul and 14 Toric horses were administered ivermectin orally at a dose of 0.2 mg/kg body weight. Blood samples were collected for 96 hr, and faecal samples were collected one day before and on days 14 and 21 after drug administration. Ivermectin concentrations in plasma samples were determined by high‐performance liquid chromatography. Ivermectin concentration was significantly higher in Toric than in Hutsul horses 90 min after ivermectin administration and was maintained at higher level for up to 96 hr. The area under the concentration versus the time curve from 0 to the last sampling point (AUC_0→t) and the maximum plasma concentration (C_max) were significantly higher in Toric than in Hutsul horses (1792.09 ± 246.22 μg × hr/L vs. 716.99 ± 255.81 μg × hr/L and 62.72 ± 17.97 ng/ml vs. 35.34 ± 13.61 ng/ml, respectively). No parasitic eggs were found in the faecal samples collected from both groups of horses on days 14 and 21 after drug administration. The obtained results indicate that although the pharmacokinetics of ivermectin may differ significantly between horse breeds, these differences do not affect the effectiveness of therapy.     

Quantitative assessment of increased sensitivity of chronic laminitic horses to hoof tester evoked pain

Reasons for performing study: To evaluate quantitative sensory testing (QST) of the feet of laminitic horses using a power‐assisted hoof tester. Hypothesis: Hoof Compression Thresholds (HCTs) can be measured reliably and are consistently lower in horses with chronic laminitis than in normal horses. Methods: HCTs of chronic laminitic (n = 7) and normal horses (n = 7) were repeatedly measured using a hydraulically powered and feedback controlled hoof tester. Data from 2 tests, at 3 sites in both forefeet, during 3 sessions were collected and statistically analysed using linear mixed models. Results: The mean ± s.e. HCT for the laminitic horses was 29.6 ± 3.5 kg/cm² and for horses in the normal group was 59.8 ± 4.3 kg/cm². Residual variance was the largest of the error components and was greater (P<0.001) for the normal horses; none of the other components significantly differed between the 2 groups. Averaging of HCTs from each foot could produce a test with intraclass correlation coefficients of 0.83 for the normal group and 0.87 for the laminitic group, with an estimated sensitivity of 0.94 and a specificity of 0.93. This test would permit detection with 80% power and 95% confidence of a reduction of over 40% in the difference in mean HCTs between laminitic and normal horses following effective treatment provided that the experimental groups are of 9 or more horses. Conclusions: HCTs can be safely and reliably measured experimentally using this hoof tester. The level of variability found indicates that, under these conditions, treatments may need to produce at least a 40% improvement to be detected. Simplification of the hoof tester, training of the horse and repeated testing may permit the method to be used clinically to detect changes in the HCTs of individual laminitic horses but these potential improvements will require further investigation. Potential relevance: Measurement of HCTs can provide an additional means for assessing the effectiveness of treatments for alleviation of chronic equine laminitis.     

The recognition of pain and learned behaviour in horses which buck

Bucking behaviour in horses is potentially dangerous to riders. There is limited information about how bucking behaviour should be investigated by veterinarians. The objectives of this article are to define bucking behaviour, to review the literature relating to bucking and allied behaviours in horses and describe personal observations and to describe an approach to clinical investigation and management strategies. A literature review from 2000 to 2020 was performed via search engines and additional free searches. A buck is an upward leap, usually in addition to forward propulsion, when either both hindlimbs or all four limbs are off the ground with the thoracolumbosacral region raised. Bucking often occurs as a series of such leaps and different manifestations include ‘pronking’, ‘bronking’ and ‘fly bucking’. Causes include excitement, exuberance, defensive behaviour associated with fear, learned behaviour through negative reinforcement or a reaction to musculoskeletal pain. Specific causes of pain include an ill-fitting saddle or girth, thoracolumbar pain, girth region pain, sternal or rib injury, neuropathic pain, sacroiliac joint region pain, referred pain and primary hindlimb lameness. Any of these may be compounded by a rider who is fearful, poorly balanced or crooked. Determination of the underlying cause requires a comprehensive clinical assessment, including assessment of saddle fit for horse and rider and suitability of the horse–rider combination. In some horses, identification of a primary source of pain allows targeted treatment and resolution of pain, but careful retraining is crucial. An understanding of learning behaviour is required for successful rehabilitation. It was concluded that identification of the cause of bucking may enable treatment of primary pain which, when combined with retraining, results in management of bucking behaviour. However, in a minority of horses, dangerous bucking behaviour cannot be reliably resolved, requiring retirement or euthanasia of the horse.     

Computed tomographic features of the temporomandibular joint in 10 Jeju horses

BackgroundThe equine temporomandibular joint (TMJ) has a complex anatomical structure that makes diagnosis of TMJ disorders difficult. Computed tomography (CT) is now available in equine medicine; hence, TMJ evaluation has become more convenient.ObjectivesThe objectives of this study were to describe the CT features of the TMJ in Jeju horses and to compare these features with those of Thoroughbreds.MethodsIn this report, the TMJs of 10 Jeju horses (mean age: 4.5 ± 1.9 yr; mean body weight: 282.6 ± 40.3 kg) and 6 Thoroughbreds (mean age: 7.3 ± 1.6 yr; mean body weight: 479.7 ± 44.0 kg) were examined using CT. After CT scanning, the Hounsfield units (HU) and height to width ratio (H:W) of the mandibular condyle were measured.ResultsThe mean H:W in Jeju horses was significantly lower than that in Thoroughbreds. The mean HU in Jeju horses was lower than that in Thoroughbreds; however, the difference was not significant. The most frequent CT finding was an irregular medial margin of the mandibular condyle in both breeds.ConclusionsIn this study, the shape of the mandibular condyle in Jeju horses was flatter than that in Thoroughbreds. This report could be useful in evaluating the TMJ in Jeju horses. Moreover, CT could be a pragmatic choice for the examination of the TMJ in horses.     

Thermography and ultrasonography in back pain diagnosis of equine athletes

The object of the current study was to evaluate the efficacy of thermography and ultrasonography in the diagnosis of thoracolumbar lesions in Quarter Horse athletes and associate the different types of lesions found with the athletic modality practiced. Twenty-four horses were admitted to the Surgery Service for Large Animals of the Veterinary and Animal Science Faculty, UNESP, Botucatu, Brazil, with complaints of back problems. All the horses were submitted for physical examinations to confirm the existence of thoracolumbar alterations and then for thermography and ultrasonography. Thermography was used to map the lesioned areas of this region and ultrasonography for lesion characterization. The lesions found were supraspinous desmitis, interspinous desmitis, dorsal intervertebral osteoarthritis, and impingement of the spinous processes or kissing spines. The existence of a relation between the type of event practiced by the horse and the type of lesion found was determined. In horses that competed in the barrel race, a predominance of lesions in the thoracic caudal, thoracolumbar, and cranial lumbar regions occurred, with intervertebral osteoarthritis and interspinous desmitis being the most common. In cutting horses, most of the lesions were observed in the caudal lumbar region, whereas horses competing in reining showed a preferential location for lesions in the middle lumbar, with a predominance of supraspinous desmitis and myositis. Thermography associated with ultrasonography was shown to be efficient in the diagnosis of the thoracolumbar lesions of these horses.     

Pharmacokinetics of potassium bromide in adult horses

OBJECTIVE: To determine the pharmacokinetics of potassium bromide (KBr) in horses after a single and multiple oral doses. ANIMALS: Twelve adult Standardbred and Thoroughbred mares. PROCEDURE: Horses were randomly assigned into two treatment groups. In Part 1 of the study, horses were given a single oral dose of 120 mg/kg KBr. Part 2 of the study evaluated a loading dose of 120 mg/kg KBr daily by stomach tube for 5 days, followed by 40 mg/kg daily in feed for 7 days. Serum concentrations of bromide were determined by colorimetric spectrophotometry following drug administration to permit determination of concentration versus time curves from which pharmacokinetic parameters could be calculated. Treated horses were monitored twice daily by clinical examination. Serum concentrations of sodium, potassium and chloride ions and partial pressures of venous blood gases were determined. RESULTS: Maximum mean serum bromide concentration following a single dose of KBr (120 mg/kg) was 284 +/- 15 microg/mL and the mean elimination half-life was 75 +/- 14 h. Repeated administration of a loading dose of KBr (120 mg/kg once daily for 5 days) gave a maximum serum bromide concentration of 1098 +/- 105 microg/mL. The administration of lower, maintenance doses of KBr (40 mg/kg once daily) was associated with decreased serum bromide concentrations, which plateaued at approximately 700 microg/mL. Administration of KBr was associated with significant but transient changes in serum potassium and sodium concentrations, and possible changes in base excess and plasma bicarbonate concentrations. High serum concentrations of bromide were associated with an apparent increase in serum chloride concentrations, when measured on an ion specific electrode. CONCLUSIONS AND CLINICAL RELEVANCE: A loading dose of 120 mg/kg daily over 5 days and maintenance doses of approximately 90-100 mg/kg of KBr administered once daily are predicted to result in serum bromide concentrations consistent with therapeutic efficacy for the management of seizures in other species. The clinical efficacy of this agent as an anticonvulsant medication and/or calmative in horses warrants further investigation.     

Effect of chiropractic manipulations on the kinematics of back and limbs in horses with clinically diagnosed back problems

REASON FOR PERFORMING STUDY: Although there is anecdotal evidence of clinical effectiveness of chiropractic in treatment of equine back pain, little scientific work has been reported on the subject. OBJECTIVES: To quantify the effect of chiropractic manipulations on back and limb kinematics in horse locomotion. METHODS: Kinematics of 10 Warmblood horses were measured over ground at walk and trot at their own, preferred speed before, and one hour and 3 weeks after chiropractic treatment that consisted of manipulations of the back, neck and pelvic area. Speed was the same during all measurements for each horse. RESULTS: Chiropractic manipulations resulted in increased flexion-extension range of motion (ROM) (P<0.05) at trot in the vertebral angular segments: T10-T13-T17 (0.3 degrees ) and T13-T17-L1 (0.8 degrees ) one hour after treatment, but decreased ROM after 3 weeks. The angular motion patterns (AMPs) of the same segments showed increased flexion at both gaits one hour after treatment (both angles 0.2 degrees at walk and 0.3 degrees at trot, P<0.05) and 3 weeks after treatment (1.0 degrees and 2.4 degrees at walk and 1.9 degrees and 2.9 degrees at trot, P<0.05). The lumbar (L3 and L5) area showed increased flexion after one hour (both angles 0.3 degrees at walk and 0.4 degrees at trot P<0.05), but increased extension after 3 weeks (1.4 degrees and 1.2 degrees , at trot only, P<0.05). There were no detectable changes in lateral bending AMPs. The inclination of the pelvis was reduced at trot one hour (1.6 degrees ) and 3 weeks (3 degrees ) after treatment (P<0.05). The mean axial rotation of the pelvis was more symmetrical 3 weeks after the treatment at both gaits (P<0.05). There were no changes in limb angles at walk and almost no changes at trot. CONCLUSIONS: The main overall effect of the chiropractic manipulations was a less extended thoracic back, a reduced inclination of the pelvis and improvement of the symmetry of the pelvic motion pattern. POTENTIAL RELEVANCE: Chiropractic manipulations elicit slight but significant changes in thoracolumbar and pelvic kinematics. Some of the changes are likely to be beneficial, but clinical trials with increased numbers of horses and longer follow-up are needed.     

Evaluation of poor performance in competition horses: A musculoskeletal perspective. Part 1: Clinical assessment

Lack of willingness to go forward freely, lack of power, shortened steps, stiffness of the cervical or thoracolumbosacral regions are common nonspecific signs of musculoskeletal causes of poor performance in sports horses. Understanding musculoskeletal causes of poor performance requires knowledge of how normal horses move, the requirements of specific work disciplines, the nomenclature used by riders to describe how a horse is performing and the interactions between horses and riders. Determining the underlying causes needs an in‐depth history and clinical assessment, including in hand, on the lunge and ridden. Ridden exercise should include all aspects with which the rider is experiencing problems. Change of the rider can sometimes help to differentiate between horse and rider problems, but most normal horses are compliant and just because a horse goes better for a more skilled rider does not preclude an underlying pain‐related condition. Lungeing and ridden exercise should include not only trot but also transitions and canter which may highlight gait abnormalities not seen at trot. An accurate history combined with thorough clinical examination of the whole horse should permit the establishment of a list of problems requiring further investigation.     

Evaluation of cervical radiographs in Dutch Warmblood horses,using a novel radiographic grading system for the cervical articular process joints

Clinical and radiographic examination of the cervical spine has been of increasing interest in the prepurchase examination and clinical work-up conducted for horses. The objective of this study was to describe a grading system useful for evaluating all the cervical articular process joints (cAPJs). Additionally, the findings of the cervical radiographs (occiput, cAPJ and intercentral joint space grading, intra- and intervertebral sagittal ratios, and intervertebral disc width measurements) were reported, and their association with clinical complaints in a large group of Dutch Warmblood horses (n = 598) were investigated. Significant associations were found between cAPJ radiographic grades and clinical complaints using the chi-squared test (C2-3 [P = 0.01], C5-6 [P = 0.006], C6-7 [P < 0.001], and C7-T1 [P = 0.02]). Higher occiput grades were significantly associated with clinical complaints (chi-squared test, P = 0.005). A large variability was found for intra- and intervertebral ratios and minimum intercentral joint space in the control group, but no significant association between intercentral joint space and clinical complaints was observed using the Kruskal–Wallis test followed by post hoc testing with the Wilcoxon rank sum test with a Bonferroni correction. The main limitations of this study were that only information regarding localisation was used for the statistical analyses, without any other details of the clinical complaints. Furthermore, clinical records were retrospectively reviewed, and a bias towards cervical findings in the clinical data recordings should be considered. It was concluded that knowledge of the distribution of the radiographic findings evaluated in this study and their associated clinical relevance can be useful in reaching a science-based diagnosis in daily practice.     

Variability of resting endoscopic grading for assessment of recurrent laryngeal neuropathy in horses

Reasons for performing study: The extent to which variability affects endoscopic grading of arytenoid cartilage movement is uncertain. Objective: To determine the observer and within horse variability of grading arytenoid cartilage movement in horses during resting endoscopic examination, using a 7‐grade system. Methods: Endoscopic recordings of the upper respiratory tract made at rest in 270 draught horses were reviewed independently by 2 veterinarians to assess interobserver variability when scoring horses' laryngeal function with a 7‐grade system. Grading was repeated by both examiners in 80 randomly selected recordings in order to assess intraobserver variability. In 120 horses, endoscopy was repeated after 24–48 h, with videos graded by both veterinarians to assess intrahorse variability. Results: The mean weighted κ statistic for concordance within examiners was 0.867, with a mean intraobserver agreement of 76.3%. The weighted κ statistic for concordance between the 2 examiners was 0.765, with an interobserver agreement of 63.1%. Of the horses receiving 2 endoscopic examinations, the same grade was assigned to 57.1% of horses at the second examination, when effects resulting from interobserver variability were removed. The mean weighted κ statistic for concordance between the grade assigned at first vs. second examinations was 0.588, indicating only moderate agreement. Conclusions and potential relevance: Intra‐ and interobserver reliability of resting endoscopic grading of arytenoid cartilage movement using a 7‐grade system was high when examinations were conducted by experienced veterinarians. However, there was moderate daily intrahorse variability, suggesting that results of resting endoscopic examinations performed on a single day should be interpreted with caution.     

Development of a composite orthopaedic pain scale in horses

This study addresses development and validation of a composite multifactorial pain scale (CPS) in an experimental equine model of acute orthopaedic pain. Eighteen horses were allocated to control (sedation with/without epidural analgesia - mixture of morphine, ropivacaine, detomidine and ketamine) and experimental groups: amphotericin-B injection in the tarsocrural joint induced pain and analgesia was either i.v. phenylbutazone administered post-induction of synovitis, or pre-emptive epidural mixture, or a pre-emptive combination of the 2. Inter- and intra-observer reproducibility was good (0.8相似文献