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.
James C, Lloyd EM, Arthur PG.The extent to which muscle strain or tears are affecting race performance in horses is unknown because it is difficult to objectively identify muscle damage. One approach includes the use of physiological markers in blood. Recently, we linked the level of plasma thiol-oxidised albumin, an oxidative stress biomarker, to muscle damage in humans. Objective: This aim of this work was to investigate whether the level of plasma thiol-oxidised albumin was elevated in the days following a thoroughbred horse race. Methods: 'In vivo' experiments. Methods: Blood collection was performed by each trainer a...
Knox AL, Fenner K, Zsoldos RR, Wilson B, McGreevy P.The off-the-track Thoroughbred's (OTTTB's) suitability for equestrian retraining and rehoming should always be subject to behavioral considerations. Certain attributes may be advantageous to a horse's racing performance but unfavorable to their prospects off the track. It is important to gain a non-biased understanding of how Thoroughbreds (TBs) in equestrian disciplines compare with other horses behaviorally, to minimize risks of poor welfare and safety outcomes. The current study used owner-reported information ( = 1633) from the Equine Behavior Assessment and Research Questionnaire (E-BARQ)...
Murase H, Wachi S, Matsuyama R, Makita K, Sato F.Pituitary pars intermedia dysfunction (PPID) is an age-related disease considered to have a negative impact on fertility. To understand the true impact of PPID on fertility, the influence of age must be considered. Objective: This study aimed to assess the impact of PPID on fertility while accounting for the effect of aging. Methods: A total of 332 Thoroughbred mares aged 10-20 years and managed across 137 private farms in Hidaka, Hokkaido, Japan were classified as PPID, equivocal, or non-PPID based on plasma adrenocorticotropic hormone concentration in 2019 and 2020. The prevalence of PPID an...
McCarthy J, Cameron-Whytock HA, Bennet ED.Thoroughbred racing is a major industry, and in recent years, public concerns about equine safety have become more prominent, particularly in relation to on-track injuries and fatalities. This has challenged the industry's social licence to operate (SLO). Objective: To investigate and elucidate how UK and Irish racing stakeholders perceive risks to racehorses on race day and how those risks should be managed. Methods: Qualitative analysis of stakeholder perspectives using a constructionist approach. Methods: Twelve stakeholders from veterinary, communication and regulatory sectors within racin...
Kuroda T, Minamijima Y, Niwa H, Mita H, Nomura M, Ohta M.A pharmacokinetics/pharmacodynamics (PK/PD) approach was used to determine the dosage regimens of trimethoprim/sulfamethoxazole for methicillin-resistant Staphylococcus aureus (MRSA) infections after intravenous (IV) and per os (PO) administration in horses. Methods: Trimethoprim/sulfamethoxazole plasma concentrations were measured in six horses after a single IV administration of 15 mg/kg (2.5 mg/kg trimethoprim and 12.5 mg/kg sulfamethoxazole) and PO administration of 30 mg/kg (5.0 mg/kg trimethoprim and 25.0 mg/kg sulfamethoxazole). The data were modeled using a nonlinear mixed-effects mode...
Qin X, Xi L, Zhao L, Han J, Qu H, Xu Y, Weng W.Gut microbiota exerts a pivotal function in host nutrient metabolism and maturation of the mucosal immunity. Analyzing the reciprocal interaction between horses and gut microbiota constitutes a crucial aspect of scientific feeding practices. This study aims to investigate the differences in gut microbiota among Hequ horses, Mongolian horses, and Thoroughbred horses, as well as between Thoroughbred horses at two age stages. Unassigned: Paired-end sequencing with a read length of 2×250 bp targeting the V3-V4 region of the 16S rRNA gene in fecal samples was carried out. Subsequently, differences...
Ruspi BD, Bramlage LR, Ruggles AJ, Slone SA.To report the rate of survival, rate of return to racing, and quality of racing performance following surgical fixation of medial condylar fractures. Methods: Retrospective study. Methods: A total of 150 Thoroughbred and Standardbred racehorses surgically treated for medial condylar fracture (100 lag screw fixation, 50 plate fixation). Methods: Medical records, radiographs, and racing databases (2000-2020) were reviewed to collect signalment, fracture characteristics, fixation methods, survival rate, and complication rate. Change in racing performance was assessed using Wilcoxon rank sum tests...
Knudsen AR, Marsh JS, Pye JL.To describe reproductive performance in Thoroughbred broodmares post-large colon resection and to compare to performance post-colopexy. Methods: A single-institution retrospective study. Methods: A total of 29 client-owned horses: post-large colon resection (LCR) n = 19, post-colopexy: n = 10. Methods: Thoroughbred broodmares that survived until discharge following LCR (Group R) or colopexy (Group P) between 2006 and 2023 were included. Clinical data were collected from clinical records. Breeding and foaling data were collected from the Australian and New Zealand Studbooks. Statistical...
Li J, Matsumoto T, Liu H, Li C, Murase H, Yamamoto Y, Nagaoka K.Accurate prediction of the timing of parturition is crucial to ensure the health and well-being of both mares and foals. However, equine pregnancies are characterised by significant variability in gestation length, unique endocrine mechanisms, and subtle physiological changes before parturition. Objective: To investigate the characteristic changes in the peripheral metabolites of mares before and after parturition using metabolomic approaches. Methods: Longitudinal in vivo metabolic study. Methods: Plasma samples (n = 95) were collected from successfully foaling Thoroughbred mares (n =â€...
Vaughan B, McKerney ER, Wollenberger C, Cloninger A, Spriet M, Galuppo L, Stover SM.Humeral stress fractures in racehorses can progress to catastrophic fracture if unrecognised. Scintigraphy is the gold standard diagnostic technique but is limited by accessibility and cost. It was hypothesised that ultrasonography could be used to visualise caudoproximal humeral stress fractures. Objective: To determine the utility of ultrasonography to identify caudoproximal humeral stress fractures in racehorses. Methods: Clinical case series. Methods: Seven racehorses that had a clinical history consistent with the presence of a humeral stress fracture were examined using humeral ultrasono...
Walz KR, McCormick ME, Fedorka CE.Breed bias exists within many of the top disciplines of equestrian sport. Therefore, the objective of this study was to evaluate the influence of breed on performance at the CCI5*-L level of eventing. To do so, the results of all CCI5*-L events from 2014 to 2024 were assessed. Initially, Thoroughbreds were compared to all non-Thoroughbreds, and this was followed by assessing the ten primary breeds. Data included penalties accrued in dressage, cross country, show jumping, and overall. Additionally, the likelihood of completing each phase was assessed. It was found that Thoroughbreds accrued mor...
Bannai H, Kambayashi Y, Kume K, Takebe N, Endo Y, Kawanishi N, Nemoto M, Tsujimura K.The endemic situation of respiratory disease caused by equine herpesvirus type-1 (EHV-1) and type-4 (EHV-4) was investigated in a training facility for Thoroughbred yearlings in Japan. Vaccination typically starts in mid-September or early October-only after all yearlings have arrived-leaving those introduced earlier unprotected. To bridge this immunity gap, a revised vaccination program that started earlier was implemented. In 2021-2022 and 2022-2023, yearlings were allocated to three groups according to their introduction dates. Each group received a live EHV-1 vaccine (Equi N Tect ERP, Niss...
Maeda Y, Kanno C, Sugiyama M, Yamamoto R, Sato S, Ando R, Noda R, Kawaguchi H, Takahashi F.A 17-year-old Thoroughbred stallion died suddenly after grazing. Necropsy revealed massive hemorrhage in the pericardial sac, suggesting cardiac tamponade. Aortic perforation was observed at the aortic origin, and hemorrhage was observed in and around the epicardium. Superficial observation of the aortic lumen revealed a transverse tear of the aortic wall at the bases of the right semilunar valve and septal semilunar valve. Fibro-osseous changes with calcification were histopathologically observed at the site of the rupture. A nodular goiter was observed in the left thyroid gland. The horse di...
Li C, Li X, Liu K, Xu J, Yu J, Liu Z, Mach N, Ni W, Liu C, Zhou P, Wang L, Hu S.Gut microbes play a vital role in host physiology, but whether specific bacterial functions contribute to the exceptional athletic performance of racehorses needs to be better understood. Here, we identify an association of gut butyrate-producing bacteria with athletic performance in racehorses (Thoroughbred horse). Butyrate-producing bacteria and microbial butyrate synthesis genes were significantly enriched in the racehorse gut, and the GC-MS results confirmed this conclusion. Using a mouse model, we demonstrated that sodium butyrate is sufficient to increase treadmill run time performance. ...
Ishimaru M, Kume K, Murase H, Sato F, Matsui A, Ohmura H, Taya K.Thoroughbreds born early in the year are believed to have an advantage in racing. However, the development of endocrine functions in early-born foals in the cold winter climate is unclear. The present study was conducted to elucidate the effect of birth month on the development of endocrine function in Thoroughbred foals born from February to May in Hokkaido by comparing hypothalamic-pituitary axis, adrenal and thyroid functions from birth to 24 weeks of age. Eighty-seven Thoroughbred foals were used to compare the changes in circulating luteinizing hormone (LH), follicle-stimulating hormone (...
Ding W, Gong W, Bou T, Shi L, Lin Y, Shi X, Li Z, Wu H, Dugarjaviin M, Bai D, Zhao Y.Speed and endurance are the primary goals in racehorse breeding. The Grassland-Thoroughbred is a newly developed breed in northern China that combines speed, endurance, and environmental adaptability. However, current research on the genetic background of this breed and the genes associated with athletic performance remains limited. We conducted whole-genome resequencing on Mongolian (MG), Thoroughbred (TB), Xilingol (XL), and Grassland-Thoroughbred (CY) horses, generating 3813.74 Gb of clean data after quality control. The number of transitions was significantly higher than that of transversi...
Ding W, Gong W, Bou T, Shi L, Lin Y, Shi X, Li Z, Wu H, Dugarjaviin M, Bai D.Copy number variation (CNV) is an important source of genetic variation. However, studies utilizing whole-genome sequencing to investigate CNVs in horse populations and their effects on traits remain relatively limited. This study aims to address the lack of research on the impact of copy number variation (CNV) on racing performance in horse populations, providing new insights for locally bred racing breeds. We analyzed 60 offspring derived from the crossbreeding of Thoroughbred horses and Xilingol horses. These horses were temporarily named "Grassland-Thoroughbred" and were divided into two g...
Kodama S, Maeda T, Mita H, Tamura N, Chiba K, Matsukawa M.Despite the prevalence of lower limb disease in racehorses, outdoor bone evaluation equipment is lacking. Consequently, a secure and cost-effective field screening system for bones is required to identify early-stage leg illness. Elastic stiffness cannot be measured using x-ray techniques and is closely associated with bone quality, which is recognized as a significant determinant of fracture risk. Quantitative ultrasound has garnered attention as a viable option, offering insights into elastic stiffness. Understanding the characteristic behaviors of ultrasonic wave properties (velocity, atten...
Soroko-Dubrovina M, Zielińska P, Dudek KD, Śniegucka K, Nawrot K.The aim of the present study was to assess the thermal effects of high-intensity laser therapy (HILT) on the temporomandibular joint (TMJ) area of clinically healthy Thoroughbred racehorses. The study was conducted on 21 clinically healthy Thoroughbreds in regular training. The horses were subjected to thermographic examinations before and immediately after a HILT session to measure changes in the body surface temperature in the TMJ area. The left TMJ was subjected to therapy, while the contralateral joint served as a control. Statistically significant differences in the body surface temperatu...
Debald DC, Stanton VL, Sandow CB, Rodgerson DH, Spirito MA, Hunt RJ, Menarim BC.While radiographically evident carpal osteochondral fragments (COF) in Thoroughbred yearlings impair sales, their impact on future racing performance has been minimally investigated. Objective: To assess the impact of COF on Thoroughbred yearling sales and racing performance, and whether these are improved by arthroscopic removal. We hypothesised that surgical removal of COF improves Thoroughbred yearling sales and racing performance. Methods: Retrospective observational. Methods: Using clinical records from years 2015-2018, 46 Thoroughbred yearlings with COF were identified and allocated to a...
Jimenez C, Hogan P, Belaghi R, Curtiss A.Epiglottitis is an uncommon upper airway pathology manifested endoscopically by mucosal oedema, reddening and thickening of the epiglottic mucosa. Literature on epiglottitis in horses is sparse. Objective: To describe the diagnosis, treatment and outcome of Thoroughbred and Standardbred racehorses diagnosed with epiglottitis at a single centre. A secondary objective is to demonstrate the efficacy of inhaled and topical anti-inflammatories for this condition. Methods: Retrospective case series. Methods: Medical records (2009-2023) were reviewed for racehorses treated for epiglottitis. Data coll...
Warren AS, Werner LA, Thombs LA, Rodgerson DH, Spirito MA, Sandow CB, McCracken MJ.To report the impact of ventral midline colopexy on colic, recurrence of large colon volvulus (LCV) and time to next live foal. Methods: Retrospective case control study. Methods: A total of 188 Thoroughbred broodmares surgically treated for LCV (2016-2020). Methods: Horses treated for LCV were grouped based on whether they received a colopexy (CP) or did not (NCP). All broodmares that underwent a second LCV surgery were subsequently categorized into two groups: those that received a colopexy (RCP) and those that did not (NRCP). Differences in the number of horses with large colon compromise, ...
Dash RF, Perkins JD, Chang YM, Morgan RE.Temporohyoid osteoarthropathy (THO) is characterised by bone proliferation and cartilage ossification caused by infectious and degenerative conditions, amongst others. Objective: To describe the variable appearance of the temporohyoid joint (THJ) on computed tomography (CT) and investigate associations between CT changes and potential risk factors. Methods: Cross-sectional study. Methods: Head CT examinations were assessed. A grading system was developed for osseous proliferation (grade 0 [normal] to 3 [severe]) and tympanohyoid cartilage change (grade 0 [normal] to 3 [complete ossification])....
Ciamillo SA, Bills KW, Gassert TM, Richardson DW, Brown KA, Stefanovski D, Ortved KF.Stress-induced bone injury can lead to catastrophic injuries in Thoroughbred racehorses. Accumulation of high-speed exercise can increase the risk of subchondral bone injury. Objective: To investigate the effect of high-speed exercise on the subchondral bone of the metacarpo-metatarsophalangeal (MCP/MTP) joints using standing cone-beam computed tomography (CBCT) in young racing Thoroughbreds. Methods: Observational cohort study. Methods: Forty-one 2-year-old Thoroughbred racehorses during their first year of training were evaluated at 0, 6 and 12 months. Horses were evaluated for lameness an...
Findley JA, Bladon BM, O'Neill HD.Sagittal plane fractures of the proximal phalanx (P1) are commonly observed in the UK Thoroughbred racehorse, with the technique and outcome following standing lag screw fixation widely reported. Long frontal plane P1 fractures propagating from the central third of the proximal articular surface occur less frequently, with information concerning repair methods and outcomes currently lacking. Objective: To describe a surgical technique for standing lag screw fixation of long frontal P1 fractures and report on post-operative performance in a UK Thoroughbred population. Methods: Single centre ret...
Volding DM, Flores-Ahlschwede P, Cramer MJ, Landrock KK, Sayre KC, Welsh TH, Bordin AI, Piccione J, Cohen ND.To determine the effects of transfusion of Rhodococcus equi hyperimmune plasma (REHIP) on serum electrolyte and protein concentrations in neonatal foals. Unassigned: A prospective observational study of 355 privately owned Thoroughbred foals from 13 farms in New York and cross-sectional study of REHIP samples. Blood was collected immediately before and after transfusion of either 1 or 2 L of REHIP to foals, and serum samples were separated and frozen until tested for concentrations of sodium (Na), potassium (K), chloride (Cl), total protein (TP), albumin, and globulins. Samples (n = 90) of REH...
Sohn Y, An SJ, Forbes E, Kim BS, Jeon HS, Ryu SH, Lee I.The lateral trochlear ridge of the stifle joint is highly susceptible to developing Osteochondrosis (OC)/Osteochondritis dissecans (OCD) lesions. This retrospective study evaluated the medical and racing outcomes of 75 Thoroughbreds who underwent arthroscopic OCD removal at the Jeju Stud Farm Equine Hospital from 2015 to 2017. The analysis included medical records, radiographic assessments, and race performance data, comparing 75 horses that underwent surgery with 257 control horses selected as siblings from the same dam. The surgical group had comparable racehorse registration rates (89.3 %...
Drahonovska A, Bladon BM, O'Neill HD.To describe a technique and report outcomes for internal fixation of short frontal-plane fractures involving the dorsoproximal articular surface of the proximal phalanx (P1) in standing horses. Methods: Short case series. Methods: Six Thoroughbred racehorses with short, frontal plane fractures involving the dorsoproximal P1. Methods: All fractures were located in the hindlimb. Horses presented with moderate lameness and marked effusion of the affected metatarsophalangeal joint. Fractures had a medial bias extending from the central aspect of proximal P1 to involve the dorsomedial prominence. F...
Renaudin CD, Picandet V, Kass PH.Using the equation of Hartwig et al. and the table established for light breed horses, day of gestation was predicted in 108 Warmblood (WB) and 59 racehorses (Thoroughbred [TB] and Standardbred [STB]) pregnant mares. In WB, gestational ages were predicted within 2 weeks from 100 to 200 days of gestation using biparietal diameter (BPD), aortic diameter (AortD) or femur length (FL); within 2 weeks from 100 to 250 days using BPD or AortD; within 2 weeks from 100 to 300 days using BPD alone; and within 3 weeks from 100 to 350 days using eye approximated volume (EyV) alone. In the ...
Szabó L, Pollard D, Nagy A.There are no published reference ranges on computed tomographic (CT) hoof wall and sole measurements. Objective: To establish reference ranges for CT measurements of the hoof wall and sole in non-lame horses, and to investigate associations between measurements and signalment, laterality, and medial or lateral sides. Methods: Retrospective, cross-sectional study. Methods: Soft tissue reconstructions of fan-beam CT studies of 110 front feet of 56 non-lame horses (30 Thoroughbred racehorses, 26 Warmblood showjumpers), performed in non- to semi-weightbearing positions, were analysed. Hoof wall th...
Johnson BJ, Stover SM, Daft BM, Kinde H, Read DH, Barr BC, Anderson M, Moore J, Woods L, Stoltz J.Necropsies were performed on 496 horses that had a fatal injury or illness at a California racetrack during the period February 20th 1990 to March 1st 1992. The primary cause of death was categorised by breed, activity at time of injury or illness and organ system affected. Most of the submissions were Thoroughbred horses (432) and Quarter Horses (46). Most of the injuries occurred while racing (42%) and in training sessions (39%); with fewer non-exercise (12%) and accident (7%) related injuries or illnesses. Musculoskeletal injuries accounted for 83% of the Thoroughbred and 80% of the Quarter...
Wallner B, Palmieri N, Vogl C, Rigler D, Bozlak E, Druml T, Jagannathan V, Leeb T, Fries R, Tetens J, Thaller G, Metzger J, Distl O, Lindgren G....The Y chromosome directly reflects male genealogies, but the extremely low Y chromosome sequence diversity in horses has prevented the reconstruction of stallion genealogies [1, 2]. Here, we resolve the first Y chromosome genealogy of modern horses by screening 1.46 Mb of the male-specific region of the Y chromosome (MSY) in 52 horses from 21 breeds. Based on highly accurate pedigree data, we estimated the de novo mutation rate of the horse MSY and showed that various modern horse Y chromosome lineages split much later than the domestication of the species. Apart from few private northern Euro...
Bower MA, McGivney BA, Campana MG, Gu J, Andersson LS, Barrett E, Davis CR, Mikko S, Stock F, Voronkova V, Bradley DG, Fahey AG, Lindgren G....Selective breeding for speed in the racehorse has resulted in an unusually high frequency of the C-variant (g.66493737C/T) at the myostatin gene (MSTN) in cohorts of the Thoroughbred horse population that are best suited to sprint racing. Here we show using a combination of molecular- and pedigree-based approaches in 593 horses from 22 Eurasian and North-American horse populations, museum specimens from 12 historically important Thoroughbred stallions (b.1764-1930), 330 elite-performing modern Thoroughbreds and 42 samples from three other equid species that the T-allele was ancestral and there...
Madigan JE, Gribble D.Case records of horses with equine ehrlichiosis (Ehrlichia equi) at the University of California Veterinary Medical Teaching Hospital and Ackerman Creek Large Animal Clinic were analyzed for evaluation of clinical signs, time of onset, hematologic values, response to treatment, and recovery. Equine ehrlichiosis was found to be seasonal in horses in the foothills of northern California, with higher incidence than reported previously. The horses developed fever, anorexia, depression, limb edema, icterus, and ataxia. Hematologic changes were leukopenia, thrombocytopenia, icterus, anemia, and incl...
Newton JR, Daly JM, Spencer L, Mumford JA.Between March and May 2003, equine influenza virus infection was confirmed as the cause of clinical respiratory disease among both vaccinated and unvaccinated horses of different breeds and types in at least 12 locations in the UK. In the largest outbreak, 21 thoroughbred training yards in Newmarket, with more than 1300 racehorses, were affected, with the horses showing signs of coughing and nasal discharge during a period of nine weeks. Many of the infected horses had been vaccinated during the previous three months with a vaccine that contained representatives from both the European (A/eq/Ne...
McGivney BA, McGettigan PA, Browne JA, Evans AC, Fonseca RG, Loftus BJ, Lohan A, MacHugh DE, Murphy BA, Katz LM, Hill EW.Digital gene expression profiling was used to characterize the assembly of genes expressed in equine skeletal muscle and to identify the subset of genes that were differentially expressed following a ten-month period of exercise training. The study cohort comprised seven Thoroughbred racehorses from a single training yard. Skeletal muscle biopsies were collected at rest from the gluteus medius at two time points: T(1) - untrained, (9 +/- 0.5 months old) and T(2) - trained (20 +/- 0.7 months old). Results: The most abundant mRNA transcripts in the muscle transcriptome were those involved in mus...
Wood JL, Newton JR, Chanter N, Mumford JA.Respiratory disease is important in horses, particularly in young Thoroughbred racehorses, and inflammation that is detected in the trachea and bronchi (termed inflammatory airway disease [IAD]) is more significant in this population in terms of impact and frequency than other presentations of respiratory disease. IAD, which is characterized by neutrophilic inflammation, mild clinical signs, and accumulation of mucus in the trachea, may be multifactorial, possibly involving infections and environmental and immunological factors, and its etiology remains unclear. This 3-year longitudinal study ...
Begg LM, O'Sullivan CB.To report the prevalence and distribution of gastric ulceration within a group of racehorses and to describe the endoscopic appearance of gastric antrum and pyloric ulceration. Methods: Retrospective clinical study. Methods: Medical records from gastroscopic examinations of 345 racehorses (331 Thoroughbreds and 14 Standardbreds) were reviewed. Prevalence, distribution and severity of gastric ulcers were recorded. Lesions involving the squamous mucosa and the glandular mucosa of the antrum and pylorus were graded and compared. Results: Gastric ulceration was found in 86% of racehorses. The squa...
Todd ET, Ho SYW, Thomson PC, Ang RA, Velie BD, Hamilton NA.The Thoroughbred horse has played an important role in both sporting and economic aspects of society since the establishment of the breed in the 1700s. The extensive pedigree and phenotypic information available for the Thoroughbred horse population provides a unique opportunity to examine the effects of 300 years of selective breeding on genetic load. By analysing the relationship between inbreeding and racing performance of 135,572 individuals, we found that selective breeding has not efficiently alleviated the Australian Thoroughbred population of its genetic load. However, we found evidenc...
Brooks SA, Makvandi-Nejad S, Chu E, Allen JJ, Streeter C, Gu E, McCleery B, Murphy BA, Bellone R, Sutter NB.Horses, like many domesticated species, have been selected for broad variation in skeletal size. This variation is not only an interesting model of rapid evolutionary change during domestication, but is also directly applicable to the horse industry. Breeders select for complex traits like body size and skeletal conformation to improve marketability, function, soundness and performance in the show ring. Using a well-defined set of 35 measurements, we have identified and quantified skeletal variation in the horse species. We collected measurements from 1215 horses representing 65 breeds of dive...
Ely ER, Avella CS, Price JS, Smith RK, Wood JL, Verheyen KL.While fractures and tendon injuries are known to be important diseases in National Hunt (NH) racehorses during racing, there are no accurate estimates of their incidence in NH training yards. Objective: To estimate the incidence of fractures and tendon and suspensory ligament injuries (TLIs) in NH racehorses in training; to describe the injuries incurred and to compare injury incidence rates by horse age, trainer, gender and background (ex-flat vs. ex-store horses). Methods: Cohort data were collected from 14 UK NH training yards for 2 racing seasons. Daily exercise regimens and details of fra...
Haase B, Brooks SA, Schlumbaum A, Azor PJ, Bailey E, Alaeddine F, Mevissen M, Burger D, Poncet PA, Rieder S, Leeb T.White coat color has been a highly valued trait in horses for at least 2,000 years. Dominant white (W) is one of several known depigmentation phenotypes in horses. It shows considerable phenotypic variation, ranging from approximately 50% depigmented areas up to a completely white coat. In the horse, the four depigmentation phenotypes roan, sabino, tobiano, and dominant white were independently mapped to a chromosomal region on ECA 3 harboring the KIT gene. KIT plays an important role in melanoblast survival during embryonic development. We determined the sequence and genomic organization of t...
Haase B, Brooks SA, Tozaki T, Burger D, Poncet PA, Rieder S, Hasegawa T, Penedo C, Leeb T.White coat colour in horses is inherited as a monogenic autosomal dominant trait showing a variable expression of coat depigmentation. Mutations in the KIT gene have previously been shown to cause white coat colour phenotypes in pigs, mice and humans. We recently also demonstrated that four independent mutations in the equine KIT gene are responsible for the dominant white coat colour phenotype in various horse breeds. We have now analysed additional horse families segregating for white coat colour phenotypes and report seven new KIT mutations in independent Thoroughbred, Icelandic Horse, Germ...
Harris RC, Marlin DJ, Dunnett M, Snow DH, Hultman E.1. Muscle buffering capacity (beta m) and dipeptide content were measured in locomotory muscles of the Thoroughbred horse, Greyhound dog and Man. 2. Beta m and carnosine contents were highest in the horse. Anserine was only found in dog muscle. 3. The higher beta m in horse and dog muscle, compared with man, appears to be predominantly due to higher muscle contents of histidine containing dipeptides in these species.
Yamanaka T, Niwa H, Tsujimura K, Kondo T, Matsumura T.On August 2007, we encountered equine influenza epidemic by Florida sub-lineage strain (H3N8) in Japan Racing Association's facilities where 4142 racehorses in total were stabled. The number of new febrile cases sharply increased, but the occurrence was rapidly calmed down within 2 weeks. The morbidity rate in these facilities was 12.8% and the subclinical infection rate of healthy racehorses examined by rapid antigen detection tests was 19.4% at the early stage of epidemic. The serological studies along with the low morbidity rate and the existence of numbers of asymptomatically infected race...
Lyle CH, Uzal FA, McGorum BC, Aida H, Blissitt KJ, Case JT, Charles JT, Gardner I, Horadagoda N, Kusano K, Lam K, Pack JD, Parkin TD, Slocombe RF....To improve the understanding of exercise related sudden death in Thoroughbred racehorses. Objective: To describe the post mortem findings in cases of sudden death associated with exercise in 268 Thoroughbred racehorses. Methods: Gross and histological post mortem findings of 268 cases of sudden death were collated and reviewed. Cases originated from 6 racing jurisdictions around the world. Sudden death was defined as acute collapse and death in a closely observed and previously apparently healthy Thoroughbred racehorse, during, or within one hour after, exercise. Cause of death as determined b...
Vatistas NJ, Snyder JR, Carlson G, Johnson B, Arthur RM, Thurmond M, Zhou H, Lloyd KL.Although gastric ulcers have been identified relatively frequently in racing Thoroughbreds, there have been no large scale studies to determine their effect on health and performance. Two hundred and two Thoroughbred horses in active race training were selected by the attending veterinarians for gastro-endoscopic examination. Images of the stomach mucosa were stored in a digitised format for subsequent evaluation. The number of ulcers and a score of severity were determined. Gastric ulceration of the squamous mucosa was identified in 82% of horses. Seventy-three (39%) horses displayed clinical...
Waters AJ, Nicol CJ, French NP.Stereotypies are invariant and repetitive behaviour patterns that seemingly have no function, which tend to develop in captive animals faced with insoluble problems and may be indicative of reduced welfare. A 4 year prospective study of the factors influencing the development of stereotypic and redirected behaviours (abnormal behaviour) in a population of 225 young Thoroughbred and part-Thoroughbred horses was conducted between 1995 and 1999. Abnormal behaviour affected 34.7% of the population. Multivariable analysis showed that foals of low- or middle-ranking mares were less likely to develop...
Allen WR, Wilsher S, Turnbull C, Stewart F, Ousey J, Rossdale PD, Fowden AL.The interacting influences of maternal size and fetal genotype on placental and fetal development in the mare were assessed by comparing conventional within-breed Thoroughbred (Tb-in-Tb, n = 7) and Pony (P-in-P, n = 7) control pregnancies established by artificial insemination (AI) with between-breed (Tb-in-P, n = 8; deprived in utero condition and P-in-Tb, n = 7; luxurious in utero condition) experimental pregnancies established by embryo transfer. All foals were born spontaneously and the mean (+/- SEM) duration of gestation in the two groups of control mares was significantly different (P <...
Verheyen K, Price J, Lanyon L, Wood J.In order to gain insight into those training regimens that can minimise the risk of fracture in athletic populations, we conducted a large epidemiological study in racehorses. Thoroughbred racehorses provide a suitable model for studying fracture development and exercise-related risk factors in physically active populations. They represent a homogeneous population, undertaking intensive exercise programmes that are sufficiently heterogeneous to determine those factors that influence injury risk. Daily exercise information was recorded for a cohort of 1178 thoroughbreds that were monitored for ...
Witte TH, Hirst CV, Wilson AM.Stride duration, stance duration and protraction duration are key variables when describing the gaits of terrestrial animals. Together, they determine the duty factor (the fraction of the stride for which the limb maintains contact with the ground surface), from which the peak vertical force can be estimated. When an animal changes speed, these variables change at different proportions. Limited measurements of these variables and predictions of peak limb force have been undertaken for large mammals performing high-speed over-ground exercise. This study set out to make such measurements, employ...
Binns MM, Boehler DA, Lambert DH.One hundred and eighty-nine Thoroughbred horses that had won Graded Stakes races in North America were genotyped with the Illumina Equine SNP50 bead chip. Association tests using PLINK to determine whether any SNPs were associated with optimum racing distance (7 furlongs and under compared to 8-10 furlongs) identified a locus on ECA18 that was statistically significant (-log 10 EMP2=1.63) at the genome-wide level following permutation analysis (10,000 permutations). Bioinformatic analysis revealed that the two ECA18 SNPs with the highest statistical significance spanned the MSTN (myostatin) lo...
Hoffman RM, Boston RC, Stefanovski D, Kronfeld DS, Harris PA.Insulin resistance is considered a risk factor in obesity, laminitis, exertional rhabdomyolysis, and osteochondrosis. The objective was to use the minimal model to estimate glucose effectiveness (Sg) and insulin sensitivity (Si) in nonobese to obese horses initially adapted to forage only, then adapted to forage plus supplements rich in starch and sugar (SS) or fiber and fat (FF). Ten Thoroughbred geldings, with BCS of 5 (nonobese), 6 (moderately obese), and 7 to 8 (obese), were adapted to pasture and hay, allocated to two groups, and fed SS or FF in a switch-back design with 8 wk of adaptatio...
Raudsepp T, Finno CJ, Bellone RR, Petersen JL.The horse reference genome from the Thoroughbred mare Twilight has been available for a decade and, together with advances in genomics technologies, has led to unparalleled developments in equine genomics. At the core of this progress is the continuing improvement of the quality, contiguity and completeness of the reference genome, and its functional annotation. Recent achievements include the release of the next version of the reference genome (EquCab3.0) and generation of a reference sequence for the Y chromosome. Horse satellite-free centromeres provide unique models for mammalian centromer...
Metzger J, Philipp U, Lopes MS, da Camara Machado A, Felicetti M, Silvestrelli M, Distl O.Copy number variants (CNVs) have been shown to play an important role in genetic diversity of mammals and in the development of many complex phenotypic traits. The aim of this study was to perform a standard comparative evaluation of CNVs in horses using three different CNV detection programs and to identify genomic regions associated with body size in horses. Results: Analysis was performed using the Illumina Equine SNP50 genotyping beadchip for 854 horses. CNVs were detected by three different algorithms, CNVPartition, PennCNV and QuantiSNP. Comparative analysis revealed 50 CNVs that affecte...
Neundorf RH, Lowerison MB, Cruz AM, Thomason JJ, McEwen BJ, Hurtig MB.To determine the prevalence and severity of osteoarthritis in the metacarpophalangeal joints of Thoroughbred racehorses via development and validation of a quantitative macroscopic evaluation system. Methods: Metacarpophalangeal joints from 50 Thoroughbred racehorses. Methods: Joints were collected from horses that died or were euthanized within 60 days of racing. Metacarpophalangeal joints were assessed for osteoarthritic degeneration by use of macroscopic and histologic scoring systems, polarized light microscopy, and cartilage biochemical analysis. The global macroscopic score for the entir...
Wilsher S, Allen WR, Wood JL.The low productivity associated with training and racing of young Thoroughbreds (TBs) in the UK due to athletic inability, injury and disease requires further study. Objective: To identify the time points and causes of losses during growth and training phases of a cohort of 1022 TB foals born in 1999 up to the end of their third year. Methods: Movement and fate of 1022 Thoroughbred foals conceived in 1998 and born live in 1999 were monitored from birth to age 3 years. Those (n = 562) that entered training age 2 and/or 3 years with one of 161 registered trainers in Britain or Ireland in 2001/2 ...
Morris LH, Allen WR.The findings of a retrospective survey of 1393 Thoroughbred mares visiting 22 studfarms in the Newmarket region of the UK during the 1998 mating season were compared with those of a similar study undertaken in 1983. The effects of mare age and status, stallion, month of mating, application of uterine treatments and other parameters on the rates of singleton and twin conception and subsequent pregnancy losses were analysed. Mare age and status significantly affected the per cycle pregnancy rate and the incidence of pregnancy loss. Overall, the mean number of matings per oestrus was 1.12 and the...
Rizk MA, El-Sayed SA, Terkawi MA, Youssef MA, El Said el Sel S, Elsayed G, El-Khodery S, El-Ashker M, Elsify A, Omar M, Salama A, Yokoyama N....A rapid and accurate assay for evaluating antibabesial drugs on a large scale is required for the discovery of novel chemotherapeutic agents against Babesia parasites. In the current study, we evaluated the usefulness of a fluorescence-based assay for determining the efficacies of antibabesial compounds against bovine and equine hemoparasites in in vitro cultures. Three different hematocrits (HCTs; 2.5%, 5%, and 10%) were used without daily replacement of the medium. The results of a high-throughput screening assay revealed that the best HCT was 2.5% for bovine Babesia parasites and 5% for equ...
Proudman CJ, Hunter JO, Darby AC, Escalona EE, Batty C, Turner C.The intestinal bacterial community of the horse is a key determinant of intestinal and whole body health. Understanding the bacterial community structure and function is an important foundation for studies of intestinal health and disease. Objective: To describe the faecal bacterial community and volatile organic compounds (VOCs) of the faecal metabolome of healthy Thoroughbred racehorses and to characterise responses to dietary supplementation with amylase-rich malt extract. Methods: Intervention study. Methods: Faecal samples were collected noninvasively before and 6 weeks after supplementat...
