Racehorses are a distinct category of horses bred and trained for competitive racing events, characterized by their speed, agility, and stamina. These horses are primarily Thoroughbreds, Standardbreds, or Quarter Horses, each with specific attributes suited to different types of racing. The physiology and management of racehorses focus on optimizing performance through training, nutrition, and veterinary care. Research in this area often explores aspects such as biomechanics, cardiovascular health, and injury prevention. This page gathers peer-reviewed research studies and scholarly articles that investigate the physiology, training methodologies, and health management practices associated with racehorses, providing insights into the factors influencing their performance and welfare.
Barbazanges P, Richard EA, Lemonnier LC, Wouters CP, Toquet MP, Couroucé A.Cytology of airway samples is sensitive for diagnosis of exercise-induced pulmonary haemorrhage (EIPH), but the association between tracheal wash (TW) and bronchoalveolar lavage fluid (BALF) is unknown. The objective of this study was to determine whether diagnosis of EIPH, using haemosiderophages/macrophages (H/M) ratio, differs when based on TW or BALF. Methods: A prospective cross-sectional study was conducted on 102 standardbred horses in training. TW and BALF were collected concomitantly from all horses at rest (at least 24 hours after their last training or race), and their H/M ratios w...
Miglio A, Falcinelli E, Cappelli K, Mecocci S, Mezzasoma AM, Antognoni MT, Gresele P.Training has a significant effect on the physiology of blood coagulation in humans and in horses. Several hemostatic changes have been reported after exercise in the horse but data available are inconclusive. The aim of this study was to investigate platelet activation and primary platelet-related hemostasis modifications in young never-trained Thoroughbreds in the first incremental training period in order to improve knowledge on this topic. Twenty-nine clinically healthy, untrained, 2-year-old Thoroughbred racehorses were followed during their incremental 4-month sprint exercise training. Bl...
Ciamillo SA, Wulster KB, Gassert TM, Richardson DW, Brown KA, Stefanovski D, Ortved KF.Catastrophic injuries of the fetlock joints occur in Thoroughbred racehorses and are preceded by stress-induced bone injury. Early detection of subchondral bone injury is essential to prevent irreversible damage or bone failure. Objective: To investigate the use of standing, robotic cone-beam computed tomography (CBCT) for assessing longitudinal changes in subchondral bone morphology and pathology of the fetlock joints associated with race training in young Thoroughbreds. Methods: Observational cohort study. Methods: Forty-one 2-year-old Thoroughbred racehorses were recruited prior to the star...
Racehorses may experience exercise-induced bronchodilation or bronchoconstriction, with potential differences between healthy and asthmatic individuals. Objective: To identify exercise-related lung function variations by oscillometry in racehorses, compare lung function between healthy and mild equine asthma (MEA) horses, assess oscillometry's potential as a predictor of racing fitness. Methods: Prospective case-control clinical study. Methods: Fourteen Thoroughbred racehorses (5 healthy, 9 MEA) underwent a protocol including respiratory oscillometry at rest, exercise with fitness monitoring, ...
Yano R, Moriyama T, Fujimori M, Nishida T, Hanada M, Fukuma N.In racehorses, feeding a high-concentrate diet could cause abnormal fermentation in the hindgut. This feeding management regime is not suitable for the nutritional physiology of horses. However, studies on the hindgut environment have yet to be reported in Japanese draft horses, so feeding management needs to be investigated in these horses. Therefore, the objective of this study was to investigate the effects of a high-concentrate diet on hindgut fermentation in Japanese draft horses. Feces were collected from 20 male Japanese draft horses managed by two stables with different feeding designs...
Cutler C, Viljanto M, Taylor P, Hincks P, Habershon-Butcher J, Gray B, Scarth J.FG-4592 is a hypoxia-inducible factor inhibitor that has been approved for therapeutic use in some countries. This class of compounds can increase the oxygen carrying capacity of the blood and thus have the potential to be used as performance enhancing agents in sports. The purpose of this study was to investigate the detection of FG-4592 and metabolites in equine plasma and mane hair following a multiple dose oral administration to two Thoroughbred racehorses, to identify the best analytical targets for doping control laboratories. Urine samples were also analysed, and the results compared to...
Wilcox CV, Knych HK, Katzman SA, Arthur RM, Rodriguez V, Finno CJ.There are two FDA-approved bisphosphonate products, clodronate (Osphos®) and tiludronate (Tildren®), for use in horses. It is hypothesized that bisphosphonates can produce analgesic effects and prevent proper healing of microcracks in bone. Therefore, bisphosphonate use is banned in racehorses. However, bisphosphonates have a short detection window in the blood before sequestration in the skeleton, making the reliability of current drug tests questionable. Seven exercising Thoroughbred horses were administered clodronate (1.8 mg/kg i.m.), and four were administered saline. RNA was isolated...
Palomino Lago E, Baird A, Blott SC, McPhail RE, Ross AC, Durward-Akhurst SA, Guest DJ.Fractures caused by bone overloading are a leading cause of euthanasia in Thoroughbred racehorses. The risk of fatal fracture has been shown to be influenced by both environmental and genetic factors but, to date, no specific genetic mechanisms underpinning fractures have been identified. In this study, we utilised a genome-wide polygenic risk score to establish an in vitro cell system to study bone gene regulation in horses at high and low genetic risk of fracture. Candidate gene expression analysis revealed differential expression of and genes in osteoblasts derived from high- and low-risk...
Ratcliffe TOC, Robinson P, Rosanowski SM.To evaluate and compare the prognosis for Thoroughbred racehorses to return to galloping and racing with injuries to the palmaroproximal metacarpus diagnosed with MRI. Methods: 29 flat racing Thoroughbreds at the Hong Kong Jockey Club that underwent MRI between 2014 and 2022. Methods: Clinical, radiographic, ultrasonographic, and MRI reports were collected from veterinary clinical records, and these were combined with training and racing data. Horses were categorized on the basis of MRI diagnosis: (1) proximal suspensory ligament (PSL) involvement only, (2) PSL and concurrent proximal third me...
Virtanen J, Hautala K, Utriainen M, Dutra L, Eskola K, Airas N, Uusitalo R, Ahvenainen E, Smura T, Sironen T, Vapalahti O, Kant R, Virtala AK....Parapoxviruses (PPV) cause skin and mucous membrane lesions in several animal species, and of the five recognized PPVs, at least three are zoonotic. Equine PPV (EqPPV) is the sixth one initially described in humans in the United States and later in a severely sick horse in Finland in 2013-2015. In 2021-2022, a large-scale pustulo-vesicular pastern dermatitis outbreak occurred in horses all over Finland. This study aimed at analysing the outbreak, identifying and describing the causative agent, describing clinical signs, and searching for risk factors. EqPPV was identified as a probable causati...
Lin ST, Bolas NM, Peter VG, Pokora R, Patrick H, Foote AK, Sargan DR, Murray RC.Palmar/plantar osteochondral disease (POD) of the metacarpal/tarsal condyles is a common pathological finding in racehorses. Objective: To compare diagnoses, imaging details, and measurements of POD lesions between cone-beam computed tomography CT (CBCT), fan-beam CT (FBCT), and low-field magnetic resonance imaging (MRI) using macroscopic pathology as a gold standard. Methods: Cross-sectional study. Methods: Thirty-five cadaver limbs from 10 horses underwent CBCT, FBCT, MRI, and macroscopic examination. CT and MR images were examined for presence of POD, imaging details of POD, and measurement...
Knych HK, Katzman S, McKemie DS, Arthur RM, Blea J.Lidocaine is a local anesthetic that is sometimes administered in combination with epinephrine. The addition of epinephrine increases the time lidocaine remains at the site of administration, thus prolonging the duration of effect. Due to their potential to prevent the visual detection of lameness, the administration of local anesthetics is strictly regulated in performance and racehorses. Recent reports of positive regulatory findings for lidocaine in racehorses suggests a better understanding of the behavior of this drug is warranted. The objective of the current study was to describe serum ...
Massie SL, Bezugley RJ, McDonald KJ, Léguillette R.Arrhythmias are commonly reported in exercising horses, however due to regulatory constraints electrocardiograms (ECGs) are acquired during training but not competition, raising questions about the repeatability of findings. The aims were (1) compare training and competition arrhythmias and (2) describe the repeatability of arrhythmias during maximal-intensity exercise. A convenience sample of 52 healthy Thoroughbreds (aged 8.7 ± 2.5 years) competing in the World Professional Chuckwagon Association were obtained, totaling 152 training or competition ECGs (2-7 ECGs/horse). Speed, heart rate ...
Dąbrowska I, Grzędzicka J, Niedzielska A, Witkowska-Piłaszewicz O.Green coffee extract is currently of great interest to researchers due to its high concentration of chlorogenic acid (CGA) and its potential health benefits. CGA constitutes 6 to 10% of the dry weight of the extract and, due to its anti-inflammatory properties, is a promising natural supplement and agent with therapeutic applications. The purpose of our study was to discover the effects of CGA on peripheral blood mononuclear cell proliferation, and the production of pro- and anti-inflammatory cytokines as well as reactive oxidative species (ROS) in horses during exercise. According to the find...
Wong ASM, Morrice-West AV, Hitchens PL, Whitton RC.Catastrophic musculoskeletal injuries (CMI) in horses are associated with both too little and too much high-speed exercise. In order to advise trainers on training and management strategies that minimize the risk of musculoskeletal injury (MSI), a better understanding of how training practices affect MSI in racehorses is needed. Data from prospective studies relating training data and MSI are complicated by the gradual development of pathology and the effect of this on the ability of horses to train consistently prior to the identification of an injury. To circumvent this, 66 Australian Thorou...
Lo Feudo CM, Stucchi L, Stancari G, Conturba B, Bozzola C, Zucca E, Ferrucci F.In racehorses, the associations between physiological parameters obtained by exercise testing and racing results have been questioned. We hypothesized that fitness variables measured during a treadmill incremental test may be related with racing outcomes and lifetime career. Our study aimed to investigate the role of fitness parameters obtained during a treadmill test in performance evaluation and career prediction in poorly performing Standardbreds, through a retrospective review of the clinical records of 245 trotters that underwent an incremental treadmill test. Several fitness parameters w...
Scantamburlo G, Nofziger C, Paulmichl M, Vanoni S.Because of their importance as companion animals or as racehorses, horses can be treated with various drugs. Although it is known that drug withdrawal times can vary for each horse, pharmacogenetics for these animals has not been adequately studied and requires further development. Since is responsible for the metabolism of 25-30% of drugs in humans, including some used to treat horses, a study of the family in horses was conducted to define its genetic structure as well as its expression pattern in the liver. Unassigned: Genomic DNA extracted from venous blood and mRNA from fresh liver tiss...
Nath LC, Elliott A, La Gerche A, Weir J, Forbes G, Thomas G, Franklin S.Atrial fibrillation (AF) is the most common performance limiting arrhythmia in racehorses. High dose exercise and airway disease promote AF in humans. Few studies have investigated epidemiological factors associated with AF in horses. Objective: Explore variables relating to performance, exercise volume and postrace endoscopic findings in horses with AF. Methods: A total of 164 horses with poor race performance and postrace AF were compared to 321 horses with poor performance without AF (PP) and 314 horses performing to expectation (TE). Methods: Horse-level and race-level variables for horses...
Bergstrom TC, Spriet M, O'Brion J, Carpenter R.To assess 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) findings associated with metacarpal/metatarsal condylar fractures at the time of fracture repair and through healing. Methods: Prospective descriptive study. Methods: Fourteen Thoroughbred racehorses. Methods: 18F-NaF PET was performed within 4 days of surgical metacarpal/metatarsal condylar fracture repair, on both the injured and contralateral limb. Follow-up PET scans were offered at 3- and 5-months post fracture repair. Areas of abnormal uptake were assessed using a previously validated grading system. Results: Ei...
Terlinden A, Szymkowiak M, Jonville E, Hatrisse C, De Azevedo E, Coudry V, Denoix JM, Pilot-Storck F, Desquilbet L, Bertoni L.Evaluate the short-term effects of acupuncture on the dynamic manifestations of axial stiffness in steeplechase racehorses. 12 steeplechase racehorses presenting signs of axial stiffness during training. Horses were randomly assigned to either an acupuncture treatment by an experienced certified acupuncturist (n = 6) or no treatment as negative controls (6). The horses' locomotion was evaluated during training before treatment (D0) and 7 (D7) and 14 (D14) days after by their rider and trainer through a questionnaire. Additionally, the improvement of their dorsal flexibility 2 days after treatm...
Gueguen L, Henry S, Delbos M, Lemasson A, Hausberger M.(1) Background: Since antiquity, it is considered that sounds influence human emotional states and health. Acoustic enrichment has also been proposed for domestic animals. However, in both humans and animals, effects vary according to the type of sound. Human studies suggest that frequencies, more than melodies, play a key role. Low and high frequencies, music tuning frequency and even EEG slow waves used for 'neurofeedback' produce effects. (2) Methods: We tested the possible impact of such pure frequencies on racehorses' behavior and physiology. A commercial non-audible acoustic stimulus, co...
Pérez-Nogués M, López-Sanromán J, Spirito M, Manso-Díaz G.Subchondral cystic lesions (SCLs) in equines and their treatments have been mainly studied in the medial femoral condyle of the femur. SCLs in the distal extremities affecting the fetlock or interphalangeal joints are frequent, but treatment or prognosis studies in horses are currently sparse. Our objective was to compare four treatments for SCLs in the distal extremities (intralesional injection of corticosteroids, transcortical drilling, cortical screw placement, and absorbable hydroxyapatite implant placement) and report the racing prognoses for affected thoroughbred yearlings. Data from 11...
Daniel CR, Taylor SE, McPhee S, Wolfram U, Schwarz T, Sommer S, Kershaw LE.Fatigue-related subchondral bone injuries of the third metacarpal/metatarsal (McIII/MtIII) bones are common causes of wastage, and they are welfare concerns in racehorses. A better understanding of bone health and strength would improve animal welfare and be of benefit for the racing industry. The porosity index (PI) is an indirect measure of osseous pore size and number in bones, and it is therefore an interesting indicator of bone strength. MRI of compact bone using traditional methods, even with short echo times, fail to generate enough signal to assess bone architecture as water protons ar...
Oda D, Onogi A.The inheritance of racing performance in Thoroughbreds is of interest to breeders and geneticists. Therefore, the genetic parameters of racing performance have been investigated in various populations of Thoroughbreds. However, the predictability of the racing performance of a racehorse has not been assessed well. In this study, we built mixed-effects models for Japanese Thoroughbreds and assessed their predictability of racing performance. We used the average velocity as an index of racing performance and treated each category of racecourse and distance as different traits. Model selection us...
Collery A, Browne JA, O'Brien C, Sheridan JT, Murphy BA.Hair follicles (HF) represent a useful tissue for monitoring the circadian clock in mammals. Irregular light exposure causes circadian disruption and represents a welfare concern for stabled horses. We aimed to evaluate the impact of two stable lighting regimes on circadian clock gene rhythmicity in HF from racehorses. Two groups of five Thoroughbred racehorses in training at a commercial racehorse yard were exposed to standard incandescent light or a customized LED lighting system. The control group received light from incandescent bulbs used according to standard yard practice. The treatment...
Dosi MCM, Riggs CM, May J, Lee A, Cillan-Garcia E, Pagan J, McGorum BC.There is a paucity of data relating to the vitamin D status of racehorses. We hypothesised that the management of racehorses in Hong Kong (HK) predisposes to low vitamin D status unless they receive dietary supplementation. Serum concentrations of 25-hydroxyvitamin D2 (25OHD2), 25-hydroxyvitamin D3 (25OHD3) and total 25-hydroxyvitamin D (total 25OHD) for 79 non-grazing HK racehorses were compared with those for 22 racehorses training in the United Kingdom (UK) that grazed for ≥1 h/d, and for which published data exists. A nested group of 41 HK horses was sampled twice to determine the effect...
Shan R, Steel CM, Sykes B.The impact of recommended withholding periods (RWPs) for omeprazole on the recurrence of Equine Gastric Ulcer Syndrome (EGUS) is unknown. The study was designed to compare the effect of two RWPs on EGUS recurrence post-omeprazole treatment and to determine if a nutraceutical supplement would reduce EGUS recurrence when administrated during an RWP. The study was a blinded, randomized clinical trial. Part 1: Horses were allocated to an RWP0 or RWP2 and crossed over after 4-weeks. Horses received oral omeprazole once daily, except during the RWPs at the end of the treatment periods. Part 2: Horse...
Anderson KA, Morrice-West AV, Wong ASM, Walmsley EA, Fisher AD, Whitton RC, Hitchens PL.Musculoskeletal injuries in racehorses are difficult to detect prior to catastrophic breakdown. Lameness is commonly attributed to orthopaedic pain in horses, therefore, subtle lameness may be a pre-clinical sign of injury and, if identified early, could allow for preventative intervention. Our objective was to determine if facial expressions could be used to detect mild lameness as an indicator of orthopaedic pain in 'fit to race' horses. The Horse Grimace Scale (HGS) and the facial expressions in ridden horses (FEReq), were used to score images (n = 380) of mildly lame (n = 21) and non-lame ...
Oheida AH, Shalgum AA, Alrtib AM, Booker AO, Ben-Naser KM, Davies HMS.Carpal conformation is an important factor in relation to joint soundness. The equine carpometacarpal joint (CMCJ) was reported to have variations in its three palmaromedial articulations. Lacking one or more of these articulations has not been radiographically evaluated in Thoroughbred (TB) and Standardbred (SB) racehorses. The study aimed to identify the prevalence of the variation in the palmaromedial articulation of the carpometacarpal joint (PM-CMCJ) in TB and SB horses. Additionally, to detect the probability of having each of the three articulations within and between the breeds. Finall...
Steel C, Ahern B, Zedler S, Vallance S, Galuppo L, Richardson J, Whitton C, Young A.Radiographs underestimate the extent of bone injury in horses with third carpal bone (C3) fractures (Fx). We aimed to describe bone pathologies identified using computed tomography (CT) and compare the diagnostic value of digital radiography (DR) and CT in horses with C3 Fx. CT images of 15 racehorses with C3 Fx and 10 controls were reviewed (Part 1) then DR and CT images of 26 racehorses (24 Thoroughbred, 2 Standardbred) with C3 Fx (Part 2) were evaluated. Agreement on fracture geometry and concomitant bone lesions was tested between DR and CT using the kappa statistic (Part 2). For agreement...
Wilmink J, Wilson AM, Goodship AE.The high incidence of partial rupture of the superficial digital flexor tendor in the equine athlete represents a major cause for concern in the racing industry. Frequently, the lesion is localised to the central core of the tendon. This study tested the hypothesis that the site specific structural failure results from differences in the collagen fibre morphology and associated micromechanics between central and peripheral regions of the tendon. Bundles of collagen fibres were dissected from central and peripheral sites in the mid-metacarpal region of the tendon. Crimp morphology was quantifie...
Pickersgill CH, Marr CM, Reid SW.A quantitative investigation of the variation that can occur during the course of ultrasonography of the equine superficial digital flexor tendons (SDFT) was undertaken. The aim of this investigation was to use an objective measure, namely the measurement of CSA, to quantify the variability occurring during the course of the ultrasonographic assessment of the equine SDFT. The effects of 3 variables on the CSA measurements were determined. 1) Image acquisition operator (IAc): two different operators undertaking the ultrasonographic examination; 2) image analysis operator (IAn): two different op...
Doucet MY, Viel L.The objective of this study was to determine if a quantitative scoring system for evaluation of hemosiderin content of alveolar macrophages obtained by bronchoalevolar lavage provides a more sensitive test for the detection of exercise-induced pulmonary hemorrhage (EIPH) in horses than does endoscopy of the lower airways. A sample population composed of 74 Standardbred racehorses aged 2-5 years was used. Horses were grouped as either control (EIPH-negative) or EIPH-positive based on history and repeated postexertional endoscopic evaluation of the bronchial airways. Bronchoalveolar lavage was p...
Li G, Lee P, Mori N, Yamamoto I, Arai T.Continuous high intensity training may induce alterations to enzyme activities related to glucose and lipid metabolism in horses. In our study, five Thoroughbred race horses (3 male and 2 female, avg age=5 yrs old) were compared against five riding horses (1 male, 1 female, 3 gelding, avg age=13 yrs old) in terms of energy metabolism, by examining plasma malate (MDH) and lactate (LDH) dehydrogenase activities and M/L ratio. MDH is involved in NADH and ATP generation, whereas LDH can convert NADH back into NAD(+) for ATP generation. An increase in plasma M/L ratio can reflect heightened energy ...
Roy MA, Vrins A, Beauchamp G, Doucet MY.This study was performed to determine the prevalence of ulcers in the gastric squamous mucosa in Standardbred racehorses. Observations were performed at monthly intervals between the beginning of their training season and their 1st qualifying race. This study also identified risk factors at different levels of race training. Forty-eight Standardbred racehorses from 3 training stables in Quebec, Canada, were studied. Baseline historical information and gastroscopic findings were recorded at the beginning of the trial, and once a month thereafter, between December 2001 and June 2002, until the h...
Stover SM, Johnson BJ, Daft BM, Read DH, Anderson M, Barr BC, Kinde H, Moore J, Stoltz J, Ardans AA.Twenty-one horses had a complete unilateral humeral fracture during race training or racing at a California racetrack during the period 24 February 1990 to 10 July 1991. Fractures occurred approximately equally in left and right limbs, and in males and females. Most fractures occurred during training, and in 2- and 3-year-old horses. Only 5 of 16 Thoroughbred horses with known racing records had previously raced more than once, and their mean time between races was less than the time between their last race and fracture (P = 0.07). Ten of 13 humeri studied further had gross evidence of periost...
Asheim A, Lindblad G.Forty-five race-horses with arthritis of non-in-fectious type in 54 joints were treated with sodium hyaluronate intra-articularly. All joints had previously been treated without lasting success by conventional methods, such as firing, blistering or intraarticular injection of cortisone. In most cases only 1 injection of 2 ml (20 mg) sodium hyaluronate was needed. To avoid subjective evaluation, the effects of the treatment were based on the joint’s capacity of withstanding extreme stress, which means that the horse should be able to train and race again. The treatment was concentrated on the...
Raphel CF, Beech J.Of 122 horses with pleural effusion, 90 (73.8%) had pleuritis secondary to pneumonia or lung abscessation. Fifty-one horses died or were euthanatized. The highest prevalence was in Thoroughbred and Standardbred racehorses. Eleven (12.2%) horses were postsurgical patients and 22 (24.4%) horses had been transported over 500 miles. There was no relationship between final outcome and the age, sex, breed, hematologic values, or laboratory findings pertaining to pleural fluid except for the bacterial isolation of Escherichia coli from the pleural fluid, as this was more frequently associated with de...
Powell SE, Ramzan PH, Head MJ, Shepherd MC, Baldwin GI, Steven WN.The proximal metacarpal region is a common site of origin of lameness in the performance horse. A number of disease entities are recognised as causes of proximal metacarpal lameness but a definitive diagnosis is often elusive. Magnetic resonance imaging (MRI) is hypothesised to offer advantages over traditional imaging modalities in the investigation of proximal metacarpal pain. Objective: To describe clinical and imaging features of cases of lameness in racehorses arising from the proximal metacarpal region in which standing MRI identified 'bone marrow oedema-type' (BMO-type) signal patterns....
Hitchens PL, Hill AE, Stover SM. The rate of catastrophic musculoskeletal injuries (CMI) in racehorses is high in the United States compared to other countries. Few modifiable risk factors related to lameness, medication, and surgery history have been identified. To detect management factors that increase risk of CMI by comparing medical histories between horses that sustained, and horses that did not sustain, a CMI. Case-control. Racehorse necropsy data (May 2012-June 2013) were obtained through the California Horse Racing Board Postmortem Program. Attending veterinarians of Thoroughbreds (TB) and Quarter Horses (QH) tha...
Deng L, Li W, Zhong Z, Liu X, Chai Y, Luo X, Song Y, Wang W, Gong C, Huang X, Hu Y, Fu H, He M, Wang Y, Zhang Y, Wu K, Cao S, Peng G.Giardia intestinalis, a cosmopolitan zoonotic parasite, is one of the most common causes of protozoal diarrhea in both humans and animals worldwide. Although G. intestinalis has been detected in many animals, information regarding its prevalence and genotype in Chinese racehorses is scarce. In the present study, we investigated the prevalence of G. intestinalis in racehorses and performed molecular characterization of the pathogen to assess its zoonotic potential. Two hundred and sixty-four racehorse fecal samples from six equestrian clubs located in different regions of the Sichuan province o...
The Journal of heredityAugust 3, 2016
Volume 107, Issue 6 537-543 doi: 10.1093/jhered/esw042
Norton EM, Mickelson JR, Binns MM, Blott SC, Caputo P, Isgren CM, McCoy AM, Moore A, Piercy RJ, Swinburne JE, Vaudin M, McCue ME.Recurrent exertional rhabdomyolysis (RER) in Thoroughbred and Standardbred racehorses is characterized by episodes of muscle rigidity and cell damage that often recur upon strenuous exercise. The objective was to evaluate the importance of genetic factors in RER by obtaining an unbiased estimate of heritability in cohorts of unrelated Thoroughbred and Standardbred racehorses. Four hundred ninety-one Thoroughbred and 196 Standardbred racehorses were genotyped with the 54K or 74K SNP genotyping arrays. Heritability was calculated from genome-wide SNP data with a mixed linear and Bayesian model, ...
Brown CM, Kaneene JB, Taylor RF.An analysis was made of the causes of death in horses and ponies over one year of age which died suddenly (Group 1) or were found dead but were considered normal when last seen (Group 2). There were 49 animals in Group 1. Thoroughbreds were overrepresented, but there were no ponies in this group. No cause of death was found in 30.6 per cent of cases and 16.3 per cent died from each of the following causes: haemorrhage in the respiratory system, central nervous system, and adverse drug reactions. Cardiovascular lesions were the cause of death in 14.4 per cent and the remaining 3.1 per cent had ...
Lane JG, Bladon B, Little DR, Naylor JR, Franklin SH.The reliability of diagnoses of obstructive conditions of the upper respiratory tract (URT) based on examinations performed at rest vs. at exercise is controversial. Objective: To compare diagnosis of URT by endoscopy at rest with that achieved during high-speed treadmill exercise (HSTE). Objective: Endoscopy of URT at rest, when performed in isolation from other simpler techniques is unreliable in the prediction of dynamic respiratory obstructions. Methods: Endoscopic findings of 600 Thoroughbred racehorses during quiet breathing were compared with findings during high-speed treadmill exercis...
Ho EN, Leung DK, Leung GN, Wan TS, Wong AS, Wong CH, Soma LR, Rudy JA, Uboh C, Sams R.Administration studies of levamisole in horses were carried out using two different levamisole preparations, namely, levamisole hydrochloride oral bolus and levamisole phosphate injectable solution. These preparations were analysed in detail for the presence of aminorex-like impurities. Both levamisole preparations were found to contain 1-(2-mercaptoethyl)-4-phenyl-2-imidazolidinone (I) and 4-phenyl-2-imidazolidinone (II) as degradation impurities, but neither aminorex nor rexamino was detected in these preparations. After the administration of these preparations to horses, aminorex, rexamino,...
Mack SJ, Kirkby K, Malalana F, McGowan CM.Hereditary muscular disease is well described in racehorses, yet little is known about traumatic muscle disease associated with unaccustomed exercise or training. The objective of the study was to compare sedentary horses, racehorses undergoing training for the first time (unaccustomed exercise), and experienced racehorses during a training season (accustomed exercise) to investigate the effect of exercise and training on serum muscle enzyme activities and other variables. Horses were sampled prior to exercise for serum activities of aspartate amino transferase (AST), creatine kinase and other...
Cardwell JM, Wood JL, Smith KC, Newton JR.Rates of airway inflammation in young racehorses decrease with time but it is not clear whether this is associated with increasing age or time exposed to the training environment. The structure of the British National Hunt (NH) population allowed closer examination of this relationship. Objective: To compare rates of inflammatory airway disease diagnosed by tracheal sampling (trIAD), and its components, in NH racehorses by age and training history and with published rates in young racehorses. Methods: A prospective, longitudinal study was conducted on 5 NH yards over 2 years. Period sample pre...
Kawcak CE, McIlwraith CW.The results of arthroscopic surgery in the treatment of osteochondral fragmentation of the proximodorsal aspect of the first phalanx and the influence of other fetlock joint lesions on prognosis were evaluated in 336 horses. Horses were classified as: 1) returning to previous use at the same or higher class of performance; 2) returning to previous use (regardless of class of performance); or 3) failing to return to previous use. Ninety-six horses (29%) had fragmentation alone; 140 horses (42%) had fragmentation and additional fetlock lesions, and 100 horses (29%) underwent concurrent carpal ar...
Woodie JB, Ducharme NG, Kanter P, Hackett RP, Erb HN.Correct placement of sutures ('laryngeal tie-forward') in experimentally created dorsal displacement of the soft palate (DDSP) has been observed to replace the function of the thyrohyoideus muscles and prevent DDSP. Objective: The 'laryngeal tie-forward' procedure would prevent or delay the occurrence of DDSP during exercise in horses with naturally occurring DDSP and therefore improve performance. Methods: A clinical population (n = 116), mainly of racehorses was presented for treatment of naturally occurring exercise-induced DDSP. All horses underwent the 'laryngeal tie-forward' procedure. T...
McIlwraith CW, Yovich JV, Martin GS.The technique and results of arthroscopic surgery for the removal of osteochondral fragments from 1,000 carpal joints in 591 horses are reported. Of the 591 horses, 580 were racehorses (including 349 Quarter Horses and 220 Thoroughbreds). The distal aspect of the radial carpal bone was the most commonly affected site, followed by the proximal aspect of the intermediate carpal bone and distolateral aspect of the radius. More than one carpal joint was simultaneously operated on in 58.9% of the Quarter Horses and in 37.4% of the Thoroughbreds. Marked differences in the amount of damage were noted...
Nyerges-Bohák Z, Nagy K, Rózsa L, Póti P, Kovács L.Changes in heart rate and heart rate variabilty (HRV) were investigated in untrained (UT; starting their first racing season) and detrained (DT; with 1-3 years of race experience) racehorses before and after 14-week conventional training. HRV was measured at rest over 1 h between 9:00 and 10:00 AM on the usual rest day of the horses. The smallest worthwhile change (SWC) rate was calculated for all HRV parameters. UT horses had significantly higher heart rate compared to DT (P<0.001). There were no gender- or training-related differences in heart rate. The root-mean-square of successive diff...
Huovinen S, Tunnela E, Huovinen P, Kuijpers AF, Suhonen R.We report fingernail onychomycosis caused by Trichophyton equinum in a farmer who breeds racehorses. In addition to the thumbnail, T. equinum had infected one of the racehorses. Oral terbinafine cured the infection in the farmer.
Oki H, Kusunose R, Nakaoka H, Nishiura A, Miyake T, Sasaki Y.Genetic variation of the behaviour of racehorses is one of the major concerns for racehorse breeders. In this study, the heritabilities of behavioural responses to the inspections of conjunctiva, auscultation and blood sampling and the genetic correlations among them were estimated in the Thoroughbred racehorse. The estimation was done with Bayesian analysis with Gibbs sampling based on the univariate or bivariate threshold animal models. The behavioural responses were scored with four categories at the first entrance quarantine in Miho Training Center of Japan Racing Association from 1993 to ...
Peloso JG, Cohen ND, Vogler JB, Marquis PA, Hilt L.OBJECTIVE To compare bony changes of the third metacarpal bone (MC3) of Thoroughbred racehorse cadavers with (cases) or without (controls) catastrophic condylar fracture by use of standing MRI. SAMPLE 140 forelimbs from 26 case horses (both forelimbs) and 88 control horses (single forelimb). PROCEDURES Bone marrow lesions (BMLs), identified as a decrease in T1-weighted (T1W) signal and increases in T2*-weighted (T2*W) and short tau inversion recovery (STIR) signals, and dense bone volume percentage (DBVP), identified as decreases in T1W, T2*W, and STIR signals, in the distopalmar aspect of MC3...
Muirhead TL, Wichtel JJ, Stryhn H, McClure JT.Serum selenium (Se), vitamin E, and resting thyroid hormone concentrations were measured in 201 horses in Prince Edward Island (PEI). Selenium concentrations were either marginal (0.0053 to 0.1200 ppm) or deficient (< 0.0053 ppm) in 79% of horses based on current reference ranges for Se in serum. Aged and young adult pleasure horses had a higher prevalence of inadequate Se concentrations compared to racehorses and broodmares (82% and 97% versus 45% and 72%, respectively). Overall, 13% of horses had inadequate (< 200 μg/dL) serum vitamin E concentrations; most of these were young pleasure hors...
Curtiss AL, Ortved KF, Dallap-Schaer B, Gouzeev S, Stefanovski D, Richardson DW, Wulster KB.Subchondral bone pathology is common in Thoroughbred racehorses and believed to precede more serious injury. Early identification of pathology is critical to allow for intervention. Objective: To determine interobserver variability of fetlock subchondral bone lesions using cone beam and fan beam computed tomography (CBCT, FBCT) and to validate a robotics-controlled CBCT to identify fetlock subchondral bone pathology in the Thoroughbred racehorse. Methods: Prospective cohort study. Methods: FBCT and CBCT images were acquired of 25 metacarpo-/metatarsophalangeal joints of Thoroughbred racehorses...
Soroko M, Howell K, Dudek K, Henklewski R, Zielińska P.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, havi...
Manohar M, Hutchens E, Coney E.Exercise-induced pulmonary haemorrhage (EIPH) is a common occurrence in race horses. Although blood in cases of EIPH has been suspected to originate from the bronchial circulation, which receives approximately 1% of the left ventricular output, physiological evidence has recently emerged to indicate that the pulmonary circulation, which receives the entire output of the right ventricle, is a more likely source. High transmural pulmonary capillary pressures have been shown to cause breaks in the capillary endothelium, basement membrane as well as in the alveolar epithelium. Blood constituents e...
McIlwraith CW, Foerner JJ, Davis DM.The technique and results of arthroscopic surgery for the treatment of osteochondritis dissecans in 318 tarsocrural joints in 225 horses are reported. Of the 225 horses, 154 were racehorses or intended for racing. Arthroscopic surgery was an effective technique for treating osteochondritis dissecans of the tarsocrural joint. The overall functional ability and cosmetic appearance of the limbs were excellent. Post surgical follow-up information was obtained for 183 horses, of which 140 (76.5 per cent) raced successfully or performed their intended use following surgery. Of the remaining 43, 11 w...
McLellan J, Plevin S.Sesamoiditis is believed to be associated with injury to the suspensory branch attachment and is a common radiographic finding in yearling Thoroughbreds. No study has investigated relationships between yearling sesamoiditis and subsequent development of suspensory ligament branch injury (SLBI) in early racehorse training. Objective: To establish the prevalence of SLBI within a population of juvenile training racehorses and retrospectively investigate relationships between clinical signs of SLBI and sesamoiditis to determine if sesamoiditis is a risk factor for clinical suspensory branch injury...
