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.     

Equine Mandibular Fibrosarcoma in Two Horses: Clinical,Diagnostic, and Therapeutic Considerations

A 25 year old Arabian gelding (case 1) presented for a large mandibular swelling involving the caudal aspect of the left horizontal mandible and a 14 year old Quarter Horse gelding (case 2) presented for a soft tissue swelling on the labial mucosa adjacent to 304. Both horses were bright and alert on presentation. Computed tomography allowed for further characterization regarding the extent of bone penetration within the lesions. This facilitated surgical planning and resection in Case 2. Histopathology of both masses diagnosed fibrosarcomas. Case 1 was humanely euthanized due to the severity of bone involvement and the grave prognosis. Case 2 underwent a left subtotal rostral hemimandibulectomy that proved to be successful in complete resection of the fibrosarcoma with a comfortable and cosmetic post-operative outcome. Surgeries that were once deemed radical should be considered for the treatment of neoplastic masses involving the soft tissues and bony structures of the oral cavity. With the aid of computed tomography, assessment of tumor penetration into deeper tissues can be achieved, thus facilitating complete surgical excision.     

Intra-articular Infection by Scedosporium prolificans in a Horse

Two months following the surgical repair of an acute, open, comminuted, and articular fracture of the left olecranon, a 15-year-old American Saddlebred gelding presented with nonweight-bearing lameness. A fungus cultured from the cubital joint was identified as Scedosporium prolificans by sequencing of the D2 large subunit ribosomal DNA region and subsequently confirmed by phenotypic methods. Therapy with systemic fluconazole, terbinafine and intra-articular voriconazole was attempted, but was unsuccessful.     

Exophthalmos Caused by Chronic Sinusitis in a Horse: A Case of Exophthalmos Caused by Sinusitis

A 12-year-old Thoroughbred gelding exhibited a unilateral exophthalmos on the left side. There had been no other clinical symptoms, such as rhinorrhea, before the first consultation. Clinical, hematologic, plasma biochemical, cytologic, and computed tomography (CT) examinations and complete necropsy were performed. These examinations did not reveal neoplastic lesions. CT images suggested that maxillary and frontal sinuses may have been filled with fluid. Cytologic and pathologic examinations revealed that the maxillary and orbital bones were pushed up with a large amount of the inflammatory fluid effused by chronic sinusitis. The CT and cytologic examinations were of great use for differential diagnosis in this case. This was an unusual case of exophthalmos induced by deformation of the orbital bones resulting from chronic sinusitis.     

Making Sense of the Metaphor: How Acupuncture Works Neurophysiologically

Dropping the veil of mystery surrounding acupuncture's effects exposes the compelling and vibrant inner workings of acupuncture based on anatomy and physiology. Shining the light on the mechanisms of acupuncture with a methodical, scientific, and evidence-based approach to equine acupuncture holds the promise of improving treatment consistency and effectiveness. Disentangling acupuncture actions from arcane notions of body function that originated millennia ago requires in-depth study of the nervous system and modern scientific evidence. Abundant information exists concerning the connections between acupuncture anatomy, nerve stimulation, and neuromodulation of the peripheral, central, and autonomic nervous systems. This body of evidence can assist equine practitioners and researchers in approaching acupuncture from a scientific, rather than a metaphorical, platform.     

Equine Multinodular Pulmonary Fibrosis in association with asinine herpesvirus type 5 and equine herpesvirus type 5: a case report

A standardbred gelding with a history of 10 days pyrexia and lethargy was referred to the Equine Hospital at the Swedish University of Agricultural Sciences in Uppsala, Sweden.The horse had tachypnea with increased respiratory effort and was in thin body condition. Laboratory findings included leukocytosis, hyperfibrinogenemia and hypoxemia. Thoracic radiographs showed signs of pneumonia with a multifocal nodular pattern, which in combination with lung biopsy findings indicated Equine Multinodular Pulmonary Fibrosis (EMPF). EMPF is a recently described disease in adult horses with clinical signs of fever, weight loss and respiratory problems. The pathological findings include loss of functional pulmonary parenchyma due to extensive nodular interstitial fibrosis which has been related to infection with the equine herpesvirus type 5 (EHV-5). In this case, lung biopsy and tracheal wash samples tested positive for both asinine herpesvirus type 5 (AHV-5) and EHV-5 using PCR assays. The horse failed to respond to treatment and was euthanized for humane reasons. Postmortem examination confirmed the diagnosis of EMPF. This case suggests that not only EHV-5 alone should be considered in association with the development of this disease.     

Does Acupuncture Acutely Affect Heart Rate Variability in Horses?

One of the mechanisms by which acupuncture (AP) exerts its purported effects involves modulation of the autonomic nervous system. Heart rate variability (HRV) noninvasively and quantitatively assesses autonomic nervous system activity. We hypothesized that AP treatment would acutely affect HRV by affecting autonomic tone. Eleven horses received three treatments in random order on different days: AP, placement of AP needles at eight AP points; sham AP (SAP), placement of eight AP needles at non-AP points; and control, no needles inserted. A Holter monitor recorded an electrocardiogram for 40 minutes during each treatment session and was analyzed over three periods: 10 minutes of initial “baseline” before AP and/or SAP, the first 10 minutes of a 20-minute AP/SAP/control “treatment”, and the first 10 minutes “post”-AP/SAP/control. RR intervals were measured during each period after the electrocardiograms were inspected and filtered, and mean heart rate (HR), low-frequency (LF) power (0.01–0.07 Hz), high-frequency (HF) power (0.07–0.6 Hz), and LF-to-HF ratio were calculated for each period. Baseline HR decreased with sequential experiments. Within experiments, HF decreased and LF-to-HF ratio increased reciprocally with time. These results suggest that parasympathetic tone decreased over the course of the experiment, perhaps, because of the stress of being restrained. Consequently, HRV indices were either not acutely affected by AP over the intervals studied or autonomic responses to being restrained may have masked any autonomic response to AP.     

Usability of normal force distribution measurements to evaluate asymmetrical loading of the back of the horse and different rider positions on a standing horse

Pressure measurement devices in equine sports have primarily focused on tack (saddle pads and saddle fitting methods). However, saddle pressure devices may also be useful in evaluating the interaction and distribution of normal forces between the horse and rider, including rider position and riding technique. This study examined the validity, reliability, repeatability and possibilities of using a saddle pressure device to evaluate rider position. All measurements were performed using a standing horse. Validity was tested by calculating the correlation coefficient between measured normal force and the weight of the rider. Repeatability was tested by calculating intra-class correlation coefficients. The use of normal force measurements to evaluate horse–rider interaction was tested by adding a known weight to saddle or rider and collecting measurements with the rider sitting in four different positions.The device was found to be valid and reliable for force measurements when the measurement device was not replaced. The system could be used to determine the expected differences with added weight and in different rider positions. The normal force distribution measurement device proved to be a valid and reliable tool for studying the interaction between a rider and a static horse provided it is positioned carefully and consistently relative to both the horse and the saddle.     

Articular sagittal and medial parasagittal patellar fracture repair using lag screws in two mature horses

This report describes the clinical experience with internal fixation of a sagittal and a medial parasagittal patellar fracture using lag screws. Severely displaced sagittal and medial parasagittal fractures of the patella were diagnosed in 2 horses (a 10‐year‐old Thoroughbred gelding and a 5‐year‐old Thoroughbred mare) and were repaired using internal fixation. A direct approach through the fascia latae was used. In both cases, the leg was placed in full extension and the fracture was corrected by a combination of digital manipulation and application of bone reduction forceps. Articular congruency was assured by arthrotomy and digital assessment, and radiographic skyline projection. Then, the leg was placed in flexion and two 5.5 mm cortical screws with washers were inserted in lag fashion, under radiographic guidance (skyline projection). In one case, an additional 6.5 mm cancellous screw was used. Both fractures healed without evidence of degenerative joint disease. However, the first horse's wound dehisced, then healed by second intention uneventfully. The second horse was put in a sling in order to prevent lying down. Both horses were able to be used for their intended purpose. In these clinical cases, sagittal and medial parasagittal patellar fractures were treated successfully by open reduction and internal fixation. Post‐operative management in a sling was used successfully in the second case to prevent wound dehiscence.     

Severe supracondylar lysis of the third metatarsal bone due to intra‐articular haemorrhage with similarities to human pigmented villonodular synovitis: A differential diagnosis to intra‐articular neoplasia

This report describes a case of severe supracondylar lysis of the third metatarsal bone of a mature Cob gelding. The gelding presented with moderate to severe lameness and soft tissue swelling in the distal metatarsal region. A mass was present plantar to the third metatarsal bone and dorsal to the suspensory ligament branches. The mass was removed surgically, and was found to be a large blood coagulum within an enlargement of the plantar pouch of the metatarsophalangeal joint. The mass was pedunculated and attached to a region of abnormal synovium. This synovium was identified histologically as being an area of villonodular synovitis. The lesion had similarities with human pigmented villonodular synovitis. Removal of the abnormal tissue resulted in resolution of the lameness and of the lysis of the third metatarsal bone. Haemarthrosis should be considered in the list of differential diagnoses for focally mineralised soft tissue masses found within an articulation, and may be associated with pigmented villonodular synovitis.     

Pathological Findings in a Case of Equine T-Cell Lymphoma Associated with Ataxia

A 15-year-old Dutch Warmblood gelding suddenly developed incoordination and hindlimb stumbling. The horse had a history of eyelid lymphoma. Necropsy revealed yellow-white or dark reddish-brown masses adhering to the outer surface of the spinal dura mater from the first cervical vertebra to the seventh thoracic vertebra. The spinal cord close to the first cervical vertebra and the seventh thoracic vertebra was markedly compressed by the masses filling the epidural space. The masses were also observed in the larynx, eyelids, and adipose-rich tissues, including the joints and orbits. They appeared similar in shape. The mandibular, retropharyngeal, axillary, superficial inguinal, deep inguinal, and lateral iliac lymph nodes were solid and enlarged. Histologically, the masses were composed of small or medium-sized lymphocyte-like tumor cells, but atypical cells and mitotic figures were rare. There were moderate infiltrations of macrophages and multinucleated giant cells, which were occasionally ingesting the surrounding tumor cells. Immunohistochemically, the tumor cells were classified as T-cell-derived cells. Throughout the spinal cord, enlargement or loss of nerve axons, dilation of periaxonal spaces, and macrophage infiltration into periaxonal spaces were observed, mainly in the ventral funiculus. Spinal cord compression by the tumor mass was suggested as a cause of the locomotive dysfunction. This is the first report of equine lymphoma with ataxia located from the proximal cervical to middle thoracic dura mater and in joint cavities.     

Acute normovolaemic haemodilution in a Clydesdale gelding prior to partial resection of the left ventral concha under general anaesthesia

A 16‐year‐old Clydesdale gelding underwent oral extraction of tooth 210 under standing sedation with partial resection of the left ventral concha under general anaesthesia 4 days later. Due to the highly vascular nature of the surgical site, significant intraoperative haemorrhage was anticipated. A lack of compatible donor horses confirmed by crossmatching prompted an autologous donation of 6 l of blood and acute normovolaemic haemodilution using a gelatine solution immediately prior to surgery. Intraoperative haemorrhage was estimated at 5% circulating volume and autologous transfusion was commenced once haemostasis was confirmed. The horse recovered uneventfully from general anaesthesia and surgery. To our knowledge this is the first report of acute normovolaemic haemodilution used in a clinical equine case.     

Tracheal perforation managed by temporary tracheostomy in a horse

Tracheal trauma with resultant rupture is uncommonly reported in veterinary literature. We report the case of a 16-year-old Thoroughbred gelding that sustained a 1 cm longitudinal perforation of the dorsal tracheal membrane in the proximal cervical region. The horse subsequently developed dyspnoea due to acute upper respiratory obstruction secondary to severe emphysema of the guttural pouches. A temporary tracheostomy caudal to the site of tracheal perforation was performed under local anaesthesia. This procedure helped relieve the upper airway obstruction and aided resolution of the injury by diverting air away from the site of tracheal perforation. After conservative management, the gelding recovered completely.     

Occipitoatlantoaxial malformation in two non-Arabian horses

Occipitoatlantoaxial malformation was diagnosed in a 19-month-old mare of Appaloosa breeding and in a 3-year-old Quarter Horse gelding. Both horses had abnormal head and neck carriage since birth, but neurologic deficits did not become evident clinically until the horses reached 2 and 3 years of age, respectively. Palpation and manipulation of the base of the skull and cervical area proved to be useful diagnostically. Movement could not be elicited at the atlantooccipital joint but, in comparison with clinically normal horses, the range of dorsoventral motion at the atlantoaxial joint was increased. Alternate subluxation and relocation of this joint generated audible clicking sounds. Radiography revealed symmetric atlantooccipital fusion, with modification of the atlas, atlantoaxial joint, and axis. These findings were confirmed at necropsy.     

Actinomyces as a Cause of Osteomyelitis of the Nasofrontal Suture in a Gelding

A 7-year-old American Quarter Horse gelding was referred to the JT Vaughan Large Animal Teaching Hospital at Auburn University, College of Veterinary Medicine, for an investigation of a recurrent swelling of the nasofrontal region. Computed tomography examination of the skull was most consistent with a sequestrum of the left nasofrontal suture with associated focal osteomyelitis and left conchofrontal sinusitis. Surgery to remove the sequestrum, debride the devitalized bone, and flush the left conchofrontal sinus was performed. A microbial culture was obtained at the time of surgery, which yielded a mixed heavy growth of an Actinomyces species. Quantitative PCR indicated a species with 93% resemblance to Actinomyces funkei. A treatment course of two weeks of oral chloramphenicol was prescribed. At three-month follow-up, the owner reported resolution of the swelling.     

Chronic eosinophilic granulomatous tenosynovitis in a Quarter Horse mare

A 5-year-old Quarter Horse mare was presented to the Michigan State University Equine Surgery Service for evaluation of a right hind metatarsophalangeal joint injury. On presentation, the horse was a grade 4/5 lame. Radiographs and ultrasonography showed peritendinous ossification/mineralisation of soft tissue structures and digital flexor tenosynovitis with profound intracapsular mineralisation. A digital flexor tendon sheath tenoscopy was performed with a plantar annular ligament desmotomy and a manica flexoria ligament tenotomy. During surgery, a significant amount of tan granular material was found within the digital tendon sheath. Approximately 80% of this material was removed, and a sample was sent for histopathology. The horse was diagnosed with eosinophilic granulomatous tenosynovitis. Long-term follow-up revealed improvement with four treatments of intralesional triamcinolone given 2–4 weeks apart. The horse became serviceably sound (grade 1/5) and was beginning light work under the saddle approximately 5 months post-tenoscopy.     

Reliability and repeatability of thermographic examination and the normal thermographic image of the thoracolumbar region in the horse

REASONS FOR PERFORMING STUDY: Thermographic imaging is an increasingly used diagnostic tool. When performing thermography, guidelines suggest that horses should be left for 10-20 mins to 'acclimatise' to the thermographic imaging environment, with no experimental data to substantiate this recommendation. In addition, little objective work has been published on the repeatability and reliability of the data obtained. Thermography has been widely used to identify areas of abnormal body surface temperature in horses with back pathology; however, no normal data is available on the thermographic 'map' of the thoracolumbar region with which to compare horses with suspected pathology. OBJECTIVES: To i) investigate whether equilibration of the thermographic subject was required and, if so, how long it should take, ii) investigate what factors affect time to equilibration, iii) investigate the repeatability and reliability of the technique and iv) generate a topographic thermographic 'map' of the thoracolumbar region. METHODS: A total of 52 horses were used. The following investigations were undertaken: thermal imaging validation, i.e. detection of movement around the baseline of an object of constant temperature; factors affecting equilibration; pattern reproducibility during equilibration and over time (n = 25); and imaging of the thoracolumbar region (n = 27). RESULTS: A 1 degrees C change was detected in an object of stable temperature using this detection system, i.e the 'noise' in the system. The average time taken to equilibrate, ie. reach a plateau temperature, was 39 mins (40.2 in the gluteal region, 36.2 in lateral thoracic region and 40.4 in metacarpophalangeal region). Only 19% of horses reached plateau within 10-20 mins. Of the factors analysed hair length and difference between the external environment and the internal environment where the measurements were being taken both significantly affected time to plateau (P<0.05). However, during equilibration, the thermographic patterns obtained did not change, nor when assessed over a 7 day period. A 'normal' map of the surface temperature of the thoracolumbar region has been produced, demonstrating that the midline is the hottest, with a fall off of 3 degrees C either side of the midline. CONCLUSIONS: This study demonstrates that horses may not need time to equilibrate prior to taking thermographic images and that thermographic patterns are reproducible over periods up to 7 days. A topographical thermographic 'map' of the thoracolumbar region has been obtained. POTENTIAL RELEVANCE: Clinicians can obtain relevant thermographic images without the need for prior equilibration and can compare cases with thoracolumbar pathology to a normal topographic thermographic map.     

Surgical repair of synovial fistulae between a carpal hygroma,the tendon sheath of the extensor carpi radialis and the antebrachiocarpal joint in a horse

This paper reports the diagnosis and repair of synovial fistulae between a carpal hygroma and both the antebrachiocarpal (ABC) joint and the extensor carpi radialis (ECR) tendon sheath of the left carpus in a 7-year-old gelding. The communication was confirmed using contrast radiography. Arthroscopy visualised the synovial fistulae and aided in the surgical repair. The gelding made a full athletic and acceptable cosmetic recovery.     

The influence of breed,age, gender,training level and ambient temperature on forelimb and back temperature in racehorses

A previous thermographic study of racehorses identified 13 regions of interest (ROIs) for monitoring the impact of training. However, that investigation did not consider the influence of breed, age, gender or training intensity level on the temperature of ROIs. The present study adopted a multivariate analysis approach to determine whether the aforementioned factors, along with ambient temperature, significantly influenced ROI temperature in the key body regions. Thermography measurements were obtained from 53 racehorses of three breeds. Horses were in regular training for over 10 months, having 13 thermographic examinations in each racing season. Backward stepwise multiple linear regression indicated that ambient temperature and breed contributed significantly to the model for predicting ROI temperature at all 13 ROIs. Training intensity level contributed significantly to the model only at the thoracic vertebrae, the left third metacarpal bone and left fetlock joint. Neither gender nor age contributed to the model significantly at any ROI. Our data suggest that ambient temperature, breed and training level affect racehorse body surface temperature in some areas of the distal parts of the forelimbs and the back. This contributes to a better understanding of the normal range of thermographic findings in racehorses undergoing intensive training.     

Effect of Fatigue on Equine Metacarpophalangeal Joint Kinematics—A Single Horse Pilot Study

The objective was to validate a scientific method for characterizing equine metacarpophalangeal joint (MCPJ) motion in the nonfatigued and fatigued states using a single horse at trot, slow canter, and fast canter. One healthy Thoroughbred gelding exercised on a treadmill to exhaustion (fatigued state) (heart rate >190 BPM and blood lactate >10 mmol/L) while bilateral MCPJ angular data were acquired using electrogoniometry. Blood lactate and heart rate reflected transition from nonfatigued to fatigued states with increasing exercise duration and treadmill speed. Electrogoniometry consistently demonstrated: increase in mean MCPJ maximum extension angle with onset of fatigue; altered extension and flexion angular velocities with onset of fatigue; and increasing stride duration and decreasing stride frequency with onset of fatigue. The method allowed a preliminary but comprehensive characterization of the dynamic relationship between MCPJ kinematics and fatigue, prompting the need for multisubject studies that may enhance our ability to moderate exercise-related distal limb injury in equine athletes.