Thoroughbreds are a breed of horse known for their agility, speed, and spirit, often associated with horse racing and equestrian sports. Originating from crossbreeding native English mares with imported Arabian, Barb, and Turkoman stallions, Thoroughbreds have a well-documented pedigree that traces back to the late 17th and early 18th centuries. This breed is characterized by a refined head, deep chest, and long legs, contributing to their athletic capabilities. Thoroughbreds are primarily bred for their performance in racing but are also utilized in other equestrian disciplines. This page compiles peer-reviewed research studies and scholarly articles that explore the genetics, physiology, and performance characteristics of Thoroughbreds, as well as their management and welfare in various equine activities.
Todd ET, Thomson PC, Hamilton NA, Ang RA, Lindgren G, Viklund Å, Eriksson S, Mikko S, Strand E, Velie BD.Domestic animal populations are often characterised by high rates of inbreeding and low effective population sizes due to selective breeding practices. These practices can result in otherwise rare recessive deleterious alleles drifting to high frequencies, resulting in reduced fertility rates. This study aimed to identify potential recessive lethal haplotypes in the Thoroughbred horse breed, a closed population that has been selectively bred for racing performance. In this study, we identified a haplotype in the LY49B gene that shows strong evidence of being homozygous lethal, despite having h...
Flunker JC, Clouser JM, Swanberg JE.Thoroughbred horse farm workers self-report a high frequency of work-related injuries and pain. However, an analysis of Thoroughbred horse farm workers' compensation injury claims is absent from the literature, yet may benefit worker safety. We analyzed workers' compensation insurance firm data containing 2276 claims filed between 2008 and 2015. Injury frequency, cost, and lost time per cause, nature, and body part injured were examined qualitatively and via univariate tests. Factors associated with high cost and high duration lost time claims were modeled via multivariable logistic regression...
Shaffer SK, To C, Garcia TC, Fyhrie DP, Uzal FA, Stover SM.Proximal sesamoid bone (PSB) fracture is the most common fatal injury in Thoroughbred (TB) racehorses in the United States. Epidemiological and pathological evidence indicates PSB fracture is likely the acute culmination of a chronic stress-related process. However, the aetiopathogenesis of PSB fracture is poorly understood. Objective: To characterise bone abnormalities that precede PSB fracture. Methods: Two retrospective case-control groups of PSBs from TB racehorses with, and without, unilateral biaxial PSB fracture. Methods: Proximal sesamoid bones were harvested post-mortem from TB raceho...
Godlewska M, Soroko M, Zielińska P.The aim of the study was to assess the influence of high-intensity laser therapy (HILT) on vein diameter and on body surface temperature changes in the tarsal joint area in a group of clinically healthy racehorses. The hypothesis of the study was that HILT increases vein diameter and body surface temperature in healthy tissue. The study involved 16 Thoroughbreds being subjected to ultrasonographic examination to assess changes of diameter of the cranial branch of the medial saphenous vein and thermographic examination to indicate temperature change of the dorsal surface of the tarsal joint, ju...
Toishi Y, Tsunoda N, Kirisawa R.In 2017, two Thoroughbred stallions, A and B in Farms A and B, respectively, in Hokkaido in Japan showed clinical signs of equine coital exanthema (ECE). In 2020, stallion C in Farm B showed clinical signs of ECE. Eighteen mares were mated within five days before stallion A developed ECE. Ten mares that mated within 3 days before onset showed clinical signs of ECE on the external genitalia. Equine herpesvirus 3 (EHV-3) was isolated from vaginal swabs from three mares that mated within 2 days before onset. Swabs from 12 mares that mated within 4 days before onset were real-time PCR (rPCR)-posit...
Whittaker CJ, Reynolds BD, McCarthy PM, Taylor SF, Major D, Caruso KA, Smith J.A 3-year-old Thoroughbred filly presented to a referral equine hospital for surgical correction of a severe cicatricial lateral lower eyelid ectropion OD, with secondary exposure keratitis. The severity of the ectropion deemed that conventional ectropion repairs would be unsuccessful. Therefore, a soft tissue expansion device was used to create sufficient local tissue for a rotational graft with tension-relieving horizontal incisions to be performed to facilitate closure and acceptable eyelid apposition. The keratitis had resolved by two months postoperatively. There were no long-term complica...
Elzer EJ, Bramlage LR.Outcomes have been reported for a limited number of short frontal plane fractures of the proximal phalanx following nonsurgical treatment and internal fixation. Objective: To describe a new approach, arthroscopic debridement, of short frontal plane fractures of the proximal phalanx in flat-racing Thoroughbreds and post-operative racing outcome. Methods: Retrospective case-control study. Methods: Medical records of 81 Thoroughbred racehorses treated with arthroscopic debridement for frontal plane fractures of the proximal phalanx were reviewed. Diagnostic images and operative reports were used ...
Kalashnikov V, Khrabrova L, Blohina N, Zaitcev A, Kalashnikova T.The Thoroughbred (TB) horse has hugely impacted the development of horse breeding around the world. This breed has unique genetic qualities due to having had a closed studbook for approximately 300 years. In Russia, TBs have been bred since the second half of the 18th century. Here, we analyzed the genetic diversity and the inbreeding level in TB horses (n = 9680) for the period from 1990 to 2018 using polymorphisms of 17 microsatellite loci. We found that the genetic structure of the TB breed in Russia is represented by 100 alleles of panel STR (short tandem repeat) loci and has been stable f...
Henderson B, Bramlage LR, Koenig J, Monteith G.To assess the influence of humeral stress fracture location on the time to return to racing and postinjury performance of thoroughbred racehorses. Methods: Retrospective study (1992-2015). Methods: Thoroughbred racehorses (n = 131) that presented for lameness with the sole diagnosis of humeral stress fractures in the lame limb, as determined by scintigraphy or radiology. Methods: Sex, fracture site, age, starts, earnings, and average earnings per race were examined for differences in pre-stress and post-stress fracture diagnosis for the entire population as well as individual stress fracture l...
Moore-Colyer M, Tuthill P, Bannister I, Daniels S.Traditions and the economic advantage when producing big athletic Thoroughbred (TB) yearlings for sale encourage owners to feed high levels of cereals. Such diets can predispose gastric ulceration and developmental orthopedic diseases, impacting negatively on future careers. This study aimed to (1) determine if an all-fiber creep feed (total mixed fiber ration [TMFR] would sustain equal growth rates in TB foals versus a cereal-based stud cube (SC) and (2) compare pH and lactate produced by SC and TMFR in in vitro foregut and hindgut conditions. Eight TB foals in matched-pairs were fed SC or T...
Verkade ME, Hazeleger E, van de Lest CHA, Back W.Throughout the ages, humans have selected different horse breeds for their locomotor capacities. Consequently, the properties of equine locomotor tissues could have diversified because of the specific requirements of different disciplines. Therefore, this study aimed to compare biochemical properties of tendons in different equine breeds traditionally selected for racing or sports performance. We hypothesised that tendons in racing breeds would have biochemical properties that would increase strength, whereas those in sporting breeds would have more elastic properties. An ex vivo tendon tissue...
Redpath A, Marr CM, Bullard C, Hallowell GD.Atrial septal defects have been well reported in humans and dogs and the principles of intervention have been well established. In contrast, there is very little information published about these congenital anomalies in horses. True ASDs are regarded as rare and little is known about the clinical significance of these defects in horses. An 11-year-old Thoroughbred gelding with a history of poor performance was diagnosed with an atrial septal defect, measuring approximately 2 cm in diameter, on 2D transthoracic echocardiography. Real-time three-dimensional (3D) echocardiography was used to map...
Muñoz L, Sepúlveda-Calderón P, Villaguala-Pacheco C, Aqueveque CL.The aim of this research was to assess the copro-prevalence of Fasciola hepatica in owned Chilean breed horses (Equus caballus) residing in the province of Concepción, Chile. The study was carried out throughout October 2017. Samples were taken from all (100%) Chilean breed horse (124 specimens; 45 females and 79 males, aged between 7 months and 24 years old) from the Concepción province. A rectal stool sample was obtained from each animal. This was analyzed using the Army Medical School method (AMS III) technique to detect F. hepatica eggs. Information about the horse's age, sex, previous f...
Mostafa MB, Elemmawy YM.There is limited knowledge about causes of musculoskeletal injury in jumping Thoroughbred horses. The objective of this study was to describe the relationships between musculoskeletal disorders and linear and angular limb measurements acquired from photographs of horses with markers at specific reference points. The diagnosed musculoskeletal disorders in either fore or hind limbs were flexor tendonitis, suspensory ligaments desmitis, and osteoarthritis of the distal intertarsal and tarso-metatarsal and carpometacarpal joints. Lengths and angles in 17 clinically normal jumping Thoroughbred hors...
Ishii H, Obara T, Kusano K, Kijima-Suda I.Paracetamol is commonly used as an over-the-counter analgesic and antipyretic medication for humans, but not sold as a legitimate therapeutic medication for horses in Japan. However, paracetamol is commonly found in horses together with its two isomers, metacetamol and orthocetamol. We previously reported that paracetamol and orthocetamol were both present in selected feed consumed by Japanese racehorses. For the purpose of the doping control of paracetamol in local Japanese horses, we proposed establishing residue limits (Japanese residue limits, JRLs) to minimize the risk of reporting parace...
Wang W, Mukai K, Takahashi K, Ohmura H, Takahashi T, Hatta H, Kitaoka Y.The aim of this study was to investigate effects of short-term hypoxic training on lactate metabolism in the gluteus medius muscle of Thoroughbreds. Using crossover design (3 months washout), eight Thoroughbred horses were trained for 2 weeks in normoxia (F O = 21%) and hypoxia (F O = 18%) each. They ran at 95% maximal oxygen consumption (V̇O ) on a treadmill inclined at 6% for 2 min (3 days/week) measured under normoxia. Before and after each training period, all horses were subjected to an incremental exercise test (IET) under normoxia. Following the 2-week trainings, V̇O in IET ...
Knych HK, Wilson WD, Vale A, Kass PH, Steffey EP, Jones JH, Arthur RM.Although controversial, due to its reported effectiveness in attenuating bleeding associated with exercise-induced pulmonary hemorrhage (EIPH), furosemide is currently a permitted race day medication in most North American racing jurisdictions. The objective of this study was to assess the efficacy of furosemide in reducing the presence and severity of EIPH when administered 24 hr prior to strenuous treadmill exercise. Eight exercised Thoroughbred horses received saline or 250 mg of furosemide either 4 or 24 hr prior to high-speed treadmill exercise in a balanced 3-way cross-over design. Bl...
Kinnison T, Cardwell JM.Inflammatory airway disease (IAD) is a commonly diagnosed but variably defined syndrome of equine lower airway inflammation. The most recent American College of Veterinary Internal Medicine (ACVIM) consensus statement, informed by research evidence, recommends a case definition based on clinical signs (poor performance or occasional coughing of at least 3 weeks duration), increased endoscopically-visible tracheal mucus, and bronchoalveolar lavage cytology, and proposes that the condition should be termed 'mild-moderate equine asthma' (mEA). In British Thoroughbred racehorses, research to date ...
Mukai K, Ohmura H, Matsui A, Aida H, Takahashi T, Jones JH.We examined the effects of high-intensity training in normobaric hypoxia on aerobic capacity and exercise performance in horses and the individual response to normoxic and hypoxic training. Eight untrained horses were studied in a randomized, crossover design after training in hypoxia (HYP; 15.0% inspired O ) or normoxia (NOR; 20.9% inspired O ) 3 days/week for 4 weeks separated by a 4-month washout period. Before and after each training period, incremental treadmill exercise tests were performed in normoxia. Each training session consisted of 1 min cantering at 7 m/s and 2 min galloping ...
Takahashi Y, Ohmura H, Mukai K, Shiose T, Takahashi T.Horses need aggressive cooling to prevent exertional heat illness after strenuous exercise in hot and humid conditions. This study compared various methods for cooling horses in such conditions, testing the hypothesis that continual application of running water would be the most effective method to decrease core temperature. Five Thoroughbreds were exercised on a treadmill at wet-bulb globe temperature of 31.8 ± 0.1°C until their pulmonary artery temperature reached 42°C. The time until the pulmonary artery temperature returned to <39°C (t) and the rectal temperature at 30 minutes afte...
Legg KA, Cochrane DJ, Bolwell CF, Gee EK, Rogers CW.To determine the incidence of, and risk factors for, race-day jockey falls occurring in Thoroughbred flat and jumps (hurdle and steeplechase) racing. Methods: Retrospective cohort study. Methods: Incidence rates for race-day jockey falls over 14 racing seasons in New Zealand (n=421,596 race-day starts) were calculated per 1000 rides. Univariable and multivariable analyses of jockey, horse and race level risk factors were conducted with Poisson regression in a generalized linear mixed model. Results: Most races (97%, n=407,948 race starts) were flat racing with 10 races/race-day, whilst most ju...
Mizobe F, Mori M, Nagata SI, Yamashita S, Okada J, Kusano K.Ever since 'One Health' concept was introduced in early 2000s, judicious use of antimicrobials by veterinarians has become an issue of great concern. Recently, findings of anti-inflammatory effects in certain types of antimicrobials have raised a subject for discussion among racing authorities. Regulatory framework of antimicrobials in racing should be based on best interest of horse welfare and doping control perspective, but basic data on prevalence of antimicrobials are lacking. Analysis of 100 postrace urinary samples collected from 10 Japanese racecourses by targeting 21 antimicrobials us...
Tamura N, Okano A, Kuroda T, Niwa H, Kusano K, Matsuda Y, Fukuda K, Mita H, Nagata S.To clarify the detailed pharmacokinetics (PK) of orally administered voriconazole in tear fluid (TF) of horses for evaluating the efficacy of voriconazole secreted into TF against equine keratomycosis. Methods: Five healthy Thoroughbred horses. Methods: Voriconazole was administrated through a nasogastric tube to each horse at a single dose of 4.0 mg/kg. TF and blood samples were collected before and periodically throughout the 24 hours after administration. Voriconazole concentrations in plasma and TF samples were analyzed using liquid chromatography-electrospray tandem-mass spectrometry. T...
Cvitas I, Oberhänsli S, Leeb T, Dettwiler M, Müller E, Bruggman R, Marti EI.Insect bite hypersensitivity (IBH) is a Th-2, IgE-mediated dermatitis of horses caused by bites of insects of the genus Culicoides that has common features with human atopic dermatitis. Together with Th-2 cells, the epithelial barrier plays an important role in development of type I hypersensitivities. In order to elucidate the role of the epithelial barrier and of the skin immune response in IBH we studied the transcriptome of lesional whole skin of IBH-horses (IBH-LE; n = 9) in comparison to non-lesional skin (IBH-NL; n = 8) as well as to skin of healthy control horses (H; n = 9). To study t...
Dubois BB, Rodgerson DH.To describe a drilling technique for hemiepiphysiodesis of the distal lateral metacarpal physis and report the outcome of treated foals. Methods: Retrospective case series. Methods: Eleven thoroughbred foals. Methods: While horses were under general anesthesia, the lateral aspect of the distal metacarpal physis was approached through a single small incision by using a power drill. The drill bit was placed at the level of the physis under radiographic guidance. A 4.5-mm drill bit was passed several times through the lateral growth plate to remove the cartilage in a fan-like pattern. Postoperati...
Gretler SR, Finno CJ, McKemie DS, Kass PH, Knych HK.To describe the pharmacokinetics and selected pharmacodynamic variables of codeine and its metabolites in Thoroughbred horses following a single oral administration. Methods: Prospective experimental study. Methods: A total of 12 Thoroughbred horses, nine geldings and three mares, aged 4-8 years. Methods: Horses were administered codeine (0.6 mg kg) orally and blood was collected before administration and at various times until 120 hours post administration. Plasma and urine samples were collected and analyzed for codeine and its metabolites by liquid chromatography-mass spectrometry, and plas...
Wodas L, Mackowski M, Borowska A, Puppel K, Kuczynska B, Cieslak J.β-lactoglobulin is one of the most abundant milk whey proteins in many mammal species, including the domestic horse. The aim of this study was to screen for polymorphism in the equine LGB1 and LGB2 gene sequences (all exons, introns, and 5'-flanking region) and to assess potential relationship of particular genotypes with gene expression levels (measured in milk somatic cells) and milk composition traits (protein, fat, lactose, and total β-lactoglobulin content). Direct DNA sequencing analysis was performed for twelve horse breeds: Polish Primitive Horse (PPH), Polish Coldblood Horse (PCH), ...
Miller SM.Endoscopy of thoroughbred (TB) yearlings at public auctions is common in South Africa. Laryngeal function (LF) is a common concern of buyers of young TBs. Cancellation of sale because of LF abnormalities is a concern for both the vendor and the buyer, with recurrent laryngeal neuropathy (RLN) being a common cause of sale cancellation. The aim of this descriptive study was to determine the prevalence of RLN at South African premier TB yearling sales. This study was designed as a retrospective descriptive analysis of upper respiratory tract (URT) endoscopic examinations to determine RLN grade, p...
Knych HK, Arthur RM, McKemie DS, Baden RW, Seminoff K, Kass PH.Flunixin meglumine (FM) and phenylbutazone (PBZ) are potent anti-inflammatory agents and as such their potential to mask injuries that would otherwise keep a horse from training or racing is concerning. A common practice in racetrack medicine in the USA is to administer the two drugs within close proximity (24 hours apart) of each other, raising the concern of pharmacokinetic interactions and enhanced anti-inflammatory effects. Objective: Describe the pharmacokinetics and effects of PBZ on the clearance of FM when administered in close proximity as well as effects on inflammatory mediators. M...
Pollock PJ, Reardon RJ, Parkin TD, Johnston MS, Tate J, Love S.There are potential advantages to imaging the upper portion of the respiratory tract (URT) of horses during ridden exercise. With the advent of a wireless endoscope, this is now possible. However, there has been no detailed validation of the technique and findings have not been compared to ridden speed. Objective: To assess the combined use of a Dynamic Respiratory Scope (DRS) and global positioning system (GPS) receiver for examining the URT of a group of Thoroughbred racehorses randomly selected from a single flat racehorse training establishment. Methods: Horses were selected randomly from ...
Arfuso F, Giannetto C, Giudice E, Fazio F, Piccione G.The effect of exercise on platelet aggregation, albumin and nonesterified fatty acids (NEFAs) values and the correlation among these parameters were evaluated in ten clinically healthy and regularly trained Thoroughbred horses. All horses were subjected to two simulated races. Blood samples were collected by jugular venipuncture before and after the first simulated race (T0PRE and T0POST), every 7 days at rest condition for a month (T1R-T2R-T3R), and before and after the second simulated race (T4PRE and T4POST) in order to assess platelet aggregation, albumin and nonesterified fatty acids (NEF...
Overbeck W, Jäger K, Schoon HA, Witte TS.Endometritis constitutes a major problem in managing broodmares. The histological occurrence of polymorphonuclear neutrophils (PMNs) in the stratum compactum of the endometrium is accepted as the reference standard to diagnose endometritis in mares. The objective of this study was to determine the distribution of PMNs within different sampling locations of the uterus by cytological examinations and to compare it with PMN numbers in endometrial biopsies of the corresponding location. Cytological and endometrial samples were obtained from 37 uteri within 2 ± 1 hours after slaughter through smal...
Mawdsley A, Kelly EP, Smith FH, Brophy PO.A linear assessment trait evaluation system is proposed to allow quantitative description of the static conformation of the horse. Measurements were made on 27 selected traits. The system was tested initially for repeatability of measurements on 4 horses. Twenty-one of the selected traits were satisfactory and 6 proved unsatisfactory in terms of reproducibility. A population of 101, superior 2- and 3-year-old Thoroughbreds and 19 premium Thoroughbred stallions were similarly assessed. More than 65% of the traits exhibited large (CV > 10%) phenotypic variation within the sampled population. ...
Catalano DN, Coleman RJ, Hathaway MR, Neu AE, Wagner EL, Tyler PJ, McCue ME, Martinson KL.Adding breed type, height, and neck circumference to body length and girth circumference improves bodyweight (BW) estimation in different breeds of horses; however, equations have not been developed for all breed types. The objectives were to develop BW estimation equations for Miniature, saddle-type, and Thoroughbred horses using morphometric measurements. Measurements were collected on adult (≥3 years, nonpregnant) saddle-type (n = 209), adult (n = 249) and juvenile (<3 years, n = 61) Miniatures, and adult Thoroughbreds (n = 100). Personnel determined body condition score (BCS), m...
Bond SL, Hundt J, Léguillette R.Mild equine asthma is a common inflammatory airway disease of the horse. The primary treatment of mild equine asthma is corticosteroids. The purpose of this study was to investigate the effects of injected dexamethasone on relative IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p35, IL-17, IL-23, IFN-γ, Eotaxin-2 and TNF-α mRNA expression in bronchoalveolar lavage (BAL) fluid in healthy Thoroughbred horses (n = 6), and those with mild equine asthma (n = 7). Results: Horses with mild equine asthma had a significantly greater bronchoalveolar lavage mast cell percentage than healthy horses...
Pozza ME, Kaewsakhorn T, Trinarong C, Inpanbutr N, Toribio RE.Vitamin D is essential in calcium and phosphorus regulation, bone physiology, cell proliferation and epithelial integrity. Literature on vitamin D in growing horses is sparse, and the effect of age on vitamin D has not been evaluated in equids in the United States or in tropical countries. The goal of this study was to determine if there was an effect of age on serum 25(OH)D3 concentrations in equids in the US (Ohio/Kentucky) and Thailand (Chiang Rai and Kanchanaburi) during the same time of the year. Blood samples were collected from healthy ponies (n=21) and Thoroughbred foals (n=13), yearli...
Bolwell C, Rogers C, Gee E, McIlwraith W.The objective of the study was to determine the incidence of veterinary events that resulted in a horse failing to finish a race and identify risk factors for musculoskeletal injury (MSI) during a race. Data were obtained on Thoroughbred flat race starts in New Zealand between 1 August 2005 and 31 July 2011 (six racing seasons). Stipendiary Steward's reports were key-word searched to identify veterinary events that prevented a horse from finishing a race. Race data were used calculate the incidence of veterinary events per 1000 horse starts and Poisson regression was used to investigate risk f...
Eaton MD, Evans DL, Hodgson DR, Rose RJ.We examined the effect of treadmill speed and incline on O2 uptake (VO2), CO2 production, heart rate (HR), plasma lactate concentration, economy of locomotion, stride frequency, and stride length. A further aim was to examine the relationships between HR and VO2 and lactate and VO2 and whether these relationships vary with alterations in treadmill incline. The experiment was a latin square design, using five horses and five treadmill inclines (0, 2.5, 5.0, 7.5, and 10.0%). Fit Thoroughbred horses exercised for 4 min at 3 m/s at 0% slope, after which the treadmill was set to the allocated incli...
Waran NK, Robertson V, Cí·¯ord D, Kokoszko A, Marlin DJ.The effects of transporting horses facing either forwards or backwards were compared by transporting six thoroughbred horses in pairs in a lorry on one journey facing in the direction of travel, and on another journey facing away from the direction of travel, over a standard one-hour route. Heart rate monitors were used to record their heart rate before, during and after the journey and the horses' behaviour was recorded by scan sampling each horse every other minute. The average heart rate was significantly lower (P < 0.05) when the horses were transported facing backwards, and they also t...
Takahashi Y, Takahashi T, Mukai K, Ohmura H.Exercise intensity during races is considerably high. To understand how Thoroughbreds adapt to fatigue conditions, stride parameters for the first and second lap of the race (2400-m, turf) were compared. A high-speed video system was set in a right lateral position about 20 m before the finishing post, with a field view width of about 16 m. The stride frequency, the length between each limb (hind step, diagonal step, fore step, and airborne step), and stride length were measured and analyzed using a generalized linear mixed model. Compared with the first lap, the mean ± standard deviation val...
Velie BD, Hamilton NA, Wade CM.Performance data for 164,046 Thoroughbreds entered in a race or official barrier trial in Australia were provided by Racing Information Services Australia. Analyses estimating the heritability for a range of racing performance traits using a single-trait animal model were performed using ASREML-R. Log of cumulative earnings (LCE; 0.19 ± 0.01), log of earnings per race start (0.23 ± 0.02) and best race distance (0.61 ± 0.03) were all significantly heritable. Fixed effects for sex were significant (P < 0.001) for all performance traits aside from LCE (P = 0.382). With the exception of annual ...
Hernandez JA, Scollay MC, Hawkins DL, Corda JA, Krueger TM.To evaluate horseshoe characteristics and high-speed exercise history as risk factors for catastrophic musculoskeletal injury in Thoroughbred racehorses. Methods: 377 horses (37,529 race starts). Methods: Shoe characteristics included material, toe grab height, heel traction device, pads, and rim shoes. Racing variables were obtained from a computerized database. Forty-three horses that had a musculoskeletal injury and then failed to race or train for 6 months (cases) and 334 noninjured horses from the same race in which a horse was injured (controls) were compared regarding risk factors. Resu...
Nath LC, Elliott AD, Weir J, Curl P, Rosanowski SM, Franklin S.Atrial fibrillation (AF) impacts performance and horse and jockey safety. Understanding the outcomes of AF identified postrace will better inform regulatory policy. Objective: To investigate the outcomes after episodes of AF identified postrace and determine whether affected horses are at increased risk of additional episodes compared to the general racing population. Methods: Total of 4684 Thoroughbred racehorses. Methods: Race records for Thoroughbred horses racing in Hong Kong from 2007 to 2017 were reviewed. Horses that performed below expectation were examined by cardiac auscultation and ...
Wagner PD, Erickson BK, Seaman J, Kubo K, Hiraga A, Kai M, Yamaya Y.Although the horse is considered an elite athlete with a specific VO2max some 2-4 times higher than man, maximal O2 transport is compromised both by moderately severe arterial desaturation and by failure to extract all O2 from blood perfusing exercising muscle. This prompted the present study to ascertain whether correction of arterial desaturation would proportionally augment VO2max and, if so, would O2 extraction behave in a manner predicted by diffusional transport limitation. Six two year old thoroughbreds were exercised to VO2max on a treadmill each on three separate occasions breathing g...
Ronéus M, Lindholm A, Asheim A.Muscle biopsies were taken from the middle gluteal muscle in 163 healthy Thoroughbreds aged one to six years. The horses were separated according to sex and divided into four different age groups (one, two, three and four to six years). Muscle biopsies were analysed for fibre type (I, IIA and IIB), and the enzyme activities of citrate synthase, 3-OH-acyl-CoA dehydrogenase, lactate dehydrogenase and hexokinase were measured. The percentage of Type I fibres of all horses increased with age, irrespective of sex (from 9 to 16 per cent). The percentage of Type IIA fibres varied with age and sex, in...
Rubio-Martínez LM, Cruz AM, Gordon K, Hurtig MB.To characterize the mechanical properties of subchondral bone (SCB) of the distopalmar aspect of the condyles of the third metacarpal bone (MC3) and their correlations with structural aspects of MC3s in Thoroughbred racehorses. Methods: 12 pairs of MC3s from Thoroughbred racehorses euthanized for various reasons. Methods: MC3s were collected from horses with mild (n = 6) and with severe (6) SCB changes, as determined by micro-computed tomography (CT). Specimens of SCB plate and trabecular bone were cut from the distopalmar aspect of condyles and sagittal ridge and examined with 3-dimensional m...
Tanner J, Rogers C, Bolwell C, Cogger N, Gee E, Mcllwraith W.The objective was to describe the incidence of failure to finish a race in flat-racing Thoroughbreds in New Zealand as these are summary indicators of falls, injuries and poor performance. Retrospective data on six complete flat racing seasons (n = 188,615 race starts) of all Thoroughbred flat race starts from 1 August 2005 to 31 July 2011 were obtained. The incidence of failure to finish events and binomial exact 95% confidence intervals were calculated per 1000 horse starts. The association between horse-, rider- and race-level variables with the outcomes failure to finish, pulled-up/fell an...
Martinson KL, Coleman RC, Rendahl AK, Fang Z, McCue ME.Excessive BW has become a major health issue in the equine (Equus caballus) industry. The objectives were to determine if the addition of neck circumference and height improved existing BW estimation equations, to develop an equation for estimation of ideal BW, and to develop a method for assessing the likelihood of being overweight in adult equids. Six hundred and twenty-nine adult horses and ponies who met the following criteria were measured and weighed at 2 horse shows in September 2011 in Minnesota: age ≥ 3 yr, height ≥ 112 cm, and nonpregnant. Personnel assessed BCS on a scale of 1 t...
da Costa CF, Samesima N, Pastore CA.Different methodologies for electrocardiographic acquisition in horses have been used since the first ECG recordings in equines were reported early in the last century. This study aimed to determine the best ECG electrodes positioning method and the most reliable calculation of mean cardiac axis (MEA) in equines. Methods: We evaluated the electrocardiographic profile of 53 clinically healthy Thoroughbreds, 38 males and 15 females, with ages ranging 2-7 years old, all reared at the São Paulo Jockey Club, in Brazil. Two ECG tracings were recorded from each animal, one using the Dubois lead posi...
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 ...
Vallance SA, Case JT, Entwistle RC, Kinde H, Barr BC, Moore J, Anderson ML, Arthur RM, Stover SM.To determine if scapular fractures occur in racehorses with distinctive characteristics. Objective: To test the hypothesis that Thoroughbred (TB) and Quarter Horse (QH) racehorses with a scapular fracture have similar characteristics that are different from those of their respective racetrack populations. Methods: Necropsy findings, case details, last race information and career earnings for TB and QH racehorses that had a scapular fracture in California between 1990 and 2008 were retrospectively compared between breeds. Horse signalment, career earnings, career starts and race characteristics...
Rogers CW, Firth EC, McIlwraith CW, Barneveld A, Goodship AE, Kawcak CE, Smith RK, van Weeren PR.No data exist on the effects of conditioning exercise at foal age on workload and subsequent clinical injury rate during their 2- and 3-year-old racing careers. Objective: To investigate the effects of subjecting TB foals to conditioning exercise prior to the start of race training on: the workload required to reach a level of fitness sufficient to compete; and the prevalence of orthopaedic injury during the first 2 seasons of their racing careers. Methods: Twenty 18-month-old TBs, 12 subjected to conditioning exercise at foal age (CONDEX) and 8 exercised spontaneously at pasture only (PASTEX)...
Trumble TN, Brown MP, Merritt KA, Billinghurst RC.Validate use of a commercially available immunoassay for measurement of bone alkaline phosphatase (BAP) in equine serum and synovial fluid (SF), and investigate the effects of osteochondral (OC) injury in horses on BAP concentrations in serum and SF. Methods: SF was collected from 37 joints of 34 Thoroughbred (TB) racehorses undergoing arthroscopic surgery for the removal of OC fragments from either the carpal joints (n=18) or the metacarpo-/metatarsophalangeal (MP) joints (n=19). SF was also obtained from 52 joints of 16 normal TB horses, collected bilaterally from carpal joints of 10 horses ...
Reilly GC, Currey JD, Goodship AE.Exercise can have a profound effect on bone mass, but little is known of its effect on bone's material properties. In this experiment, our hypothesis was that a large difference in the training regimen of young thoroughbreds would produce a measurable difference in the mechanical properties of their bone material. When they were about 19 months old, eight thoroughbred racehorses were given one of two exercise regimens that lasted for 19 weeks: four horses (controls) were walked for 40 minutes a day but had no other exercise, and the remaining four (exercised) were additionally trotted for 20 m...
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...
Hyytiäinen HK, Mykkänen AK, Hielm-Björkman AK, Stubbs NC, McGowan CM.Although the majority of equine muscles have a mixed fibre type distribution indicative of diverse functional roles, the predominance of a fibre type can indicate the primary function of a muscle. The deep epaxial musculature has an important role in core spinal stability in humans, reflected as a predominantly muscle fibre type (MFT) I or postural fibre type. The fibre type of the deep epaxial musculature has not been determined in horses. The objective of the study was to determine the MFT distribution in selected muscles of thoracolumbar and hindlimb region of horses. This included deep epa...
Lindner AE.The speed producing the maximal lactate steady state (maxLASS) is supposed to be the optimal speed to condition for endurance. The maxLASS was defined as the maximal speed at which the blood lactate concentration ([LA]) between the 5th and the 25th min of continuous exercise did not increase by more than 1 mmol/L. According to the aerobic-anaerobic lactate threshold concept determined in humans, maxLASS corresponds to v(4) [speed in a standardized exercise test (SET) shown to produce an [LA] of 4 mmol/L; generalized to v(i) for the speed producing an [LA] of i mmol/L]. Four Thoroughbreds were ...
Fincham DA, Mason DK, Young JD.Horse erythrocytes are polymorphic with respect to L-alanine permeability. The present investigation compared the specificity, kinetics and cation-dependence of erythrocyte amino acid transport in two groups of thoroughbred horses, those with erythrocyte L-alanine permeabilities in the range 5-15 mumol/h per litre of cells (0.2 mM extracellular L-alanine, 37 degrees C) (transport-negative type) and those with L-alanine permeabilities in the range 450-700 mumol/h per litre of cells (transport-positive type). Transport-positive cells are shown to possess a novel high-affinity, stereospecific, Na...
Bithell S, Habershon-Butcher JL, Bowen IM, Hallowell GD.The aims of this study were to assess the repeatability and reproducibility of transabdominal ultrasonography to assess intestinal wall thickness in adult Thoroughbred horses (n = 8). Ultrasonographic cineloops were captured by one examiner from each horse for five consecutive days. During each examination at least three cineloops were obtained for five different intestinal tract locations. Measurements were performed by three separate observers to assess reproducibility and measured on three separate occasions by three observers to evaluate short-term repeatability. The repeatability of measu...
