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.
Hanousek K, O'Hara V, Riddell DO, Piercy RJ.In Thoroughbred horses, a highly prevalent short interspersed nuclear element (SINE) mutation in the myostatin gene (MSTN) promoter influences circulating myostatin concentration and is associated with muscle morphology, fracture risk and optimal race distance. Our prior data reveal that within horses there is substantial variation in serum myostatin concentration, particularly in MSTN heterozygotes and wild type horses but it was unclear whether such variation relates to within-horse differences or to environmental or temporal effects. Here we report the intra-horse consistency of circulating...
Takahashi K, Mukai K, Takahashi Y, Ebisuda Y, Sugiyama F, Hatta H, Kitaoka Y.To explore the molecular mechanisms underlying oxygen-dependent regulation of skeletal muscle adaptations, eight Thoroughbred horses performed 2 min of exercise at a velocity corresponding to 95% maximal O2 uptake under a normoxic condition, while using inspired O2 levels of 0.21 (normoxia), 0.26 (hyperoxia) or 0.16 (hypoxia). At the end of the exercise, arterial O2 saturation was significantly higher with hyperoxia and lower with hypoxia than with normoxia. However, no significant difference in plasma lactate or muscle glycogen concentrations was observed across the O2 conditions. A metabol...
Taned M, Zandi MB, Salek Ardestani S, Abdoli M, Spangler ML.Race performance in Thoroughbred horses is influenced by both genetic and environmental factors. Understanding their genetic architecture is essential for designing effective breeding programs. Objective: This study aimed to estimate genetic parameters and trends for key performance traits in Iranian Thoroughbred racehorses. Methods: Performance data, including race completion time (RCT), rank at the end of the competition (REC), and average speed (AS), were obtained from the Iranian Equestrian Federation (2002-2021). Pedigree data from 14,391 individuals were analyzed using CFC software. Gene...
Jacobs ME, Blea J, Hardy M, McKemie DS, Traynham M, Knych HK.The racehorse industry has strict regulations regarding the detection of prohibited substances in horses. Metformin, a diabetes medication, is a prohibited substance that has been reported in post-race blood and urine samples collected from racehorses. For further characterization of the disposition of metformin, 12 Thoroughbred horses were administered metformin orally and intravenously in a randomized, balanced, two-way crossover design. Serum and urine samples were collected, and drug concentrations determined via liquid chromatography-tandem mass spectrometry. The serum data were analyzed ...
Alexeenko V, Anchan DS, Ter Woort F, Ribonnet C, van Erck E, Marr C, Jeevaratnam K.Non-linear equine electrocardiography (ECG) analysis is an actively developing study area which has the potential to lead to novel, artificial intelligence-based diagnostic tools in equine cardiology. As more ECG recording devices are becoming available, there is a need to ensure results are interchangeable regardless of the equipment used to record the equine ECG. Objective: To evaluate the agreement of ECG complexity values obtained using the Televet™ and Equimetre™ systems. Methods: Cross-sectional clinical. Methods: ECGs were recorded using two devices simultaneously from 37 healthy Th...
Morrice-West AV, Wong ASM, Hitchens PL, Whitton RC.Musculoskeletal injuries (MSI) in racehorses are not typically spontaneous events, but develop gradually through cumulative cycles of loading over time. Stride characteristics can now be recorded with wearable technology, providing opportunity to quantify the skeletal impact of galloping over time. We estimated bone fatigue accumulation based on speed (m/s) and number of strides from n = 3168 race starts by n = 405 Thoroughbreds commencing racing in Tasmania, Australia between 2011 and 2016. The percentage bone fatigue accumulated was divided by various time periods (career, active car...
Pilger F, Aurich C, Aurich JE.The early career start of racehorses, the pretraining of two-year-old Warmblood stallions for licensing, and individual housing of young horses increasingly raise animal welfare concerns. Objective: Assess pretraining practices and the opinion of trainers on housing of young horses, minimum age to commence training and pretraining injuries. Methods: Qualitative interviews with trainers of Warmblood stallions and Thoroughbred and Trotter racehorses (n = 10 each). Results: Pretraining of Thoroughbreds and Trotters began at 18 months, whereas licensing preparation of Warmblood stallions began at ...
McDonald S, Verheyen KLP, Chang YM, Allen SE.Race-related injuries in horse racing, especially those requiring extended recovery, are a welfare concern and threaten the sport's social licence. Previous studies predominantly report on fatalities; however, serious non-fatal musculoskeletal injuries often end horses' racing careers or have a high recurrence risk. No recent studies have described or quantified long-term injuries (LTIs) in racing Thoroughbreds, which is essential to inform targeted risk prevention strategies. Objective: To describe the types, frequencies and incidences of LTIs in British jump racing. Methods: Retrospective co...
Chapple AR, Daglish J, Stover SM, Slipchenko N, Phillips KL.Stress fracture is an important cause of mortality and morbidity in racing Thoroughbreds. Nuclear scintigraphy is the imaging modality of choice for investigating unlocalised stress-related bone remodelling in horses. Stress fractures of the caudal lumbar vertebral column have been previously described in both racing Quarter horses and racing Thoroughbreds post-mortem. There is a lack of literature describing the imaging appearance of vertebral stress fractures in racehorses ante-mortem. Objective: To describe: (1) ante-mortem scintigraphic appearance of presumed thoracolumbar vertebral stress...
van den Broek M, Chan ZYS, De Bruyne C, Garcia-Alamo K, Skotarek Loch S, Pfau T.Increased risk of musculoskeletal injury in galloping racehorses has been linked to decreased stride length and reduced speed over consecutive races prior to the injury. As racetrack curvature influences horses' maximal speed, we hypothesized it also affects stride parameters. During training sessions, twenty-eight wagon-pulling Thoroughbred Chuckwagon horses were equipped with Global Navigation Satellite System (GNSS) loggers, allowing for identification of speed, stride length (SL) and stride frequency (SF), and average speed, SL and SF were calculated for consecutive 100 m sections. Effects...
Arevalo-Turrubiarte M, Edling CE, Moller-Levet C, Forbes B, Kemp V, Weir J, Marr C, Lewis R, Jeevaratnam K.The initiation and maintenance of atrial fibrillation have been associated with physiological alterations in myocardial sleeves of the pulmonary veins (PVs). Gene expression profiles of the myocardial sleeves of the PVs in healthy (n = 3) and paroxysmal atrial fibrillation (PAF) (n = 6) thoroughbred horses (Equus caballus) were studied. Tissue collected from the left superior PV, adjacent to the left atrium, was analyzed by RNA sequencing. Gene Set Enrichment Analysis demonstrated positive enrichment of gene ontology biological processes related to muscle and endothelial cell development, cell...
Feng M, Hall TJ, MacHugh DE, Katz LM, Hill EW.Early skeletal muscle development is critical for young racehorses, yet research on the transcriptional changes during this period is limited. Additionally, the impact of age on the transcriptional response to exercise training in equine athletes is not well understood. A transcriptome-wide analysis of differential gene expression in skeletal muscle was performed for five untrained Thoroughbred horses sampled at rest at two years old (UR2) and three years old (UR3). A total of 136 differentially expressed genes (DEGs) were identified, with 95 increased and 41 decreased in expression. GO enrich...
Deniz Ö, Erol HS, van den Hoven R, Onmaz AC, Aragona F, Fazio F.Weaning represents a major developmental milestone for foals, especially when 4- to 7-month-old foals are abruptly separated from their dams. Studies have shown that the post-weaning period is associated with physiological and psychological stress, which may affect immune function. The present study aimed to describe and analyze the pattern of blood inflammatory biomarkers related to the innate immune system. A gradual foal-dam separation procedure was chosen, which included post-weaning social buffering by a familiar adult horse. Twelve Thoroughbred foals (six fillies, six colts) aged 4-6 mon...
James C, Sheahan J, Arthur P.Thoroughbred race performance is influenced by genetics, training, recovery, and management, but decisions about race readiness are often subjective and lack validated physiological markers. This study evaluated thiol-oxidised albumin, a blood-based indicator of oxidative stress, as a potential biomarker of pre-race fitness in Australian Thoroughbreds. Seventy-five clinically healthy racehorses from seven stables were monitored across 216 competitive events (150 races, 66 trials). Blood samples were collected from the jugular at baseline, 48 h pre-race, and for each day up to 8 days post-race ...
Ryder E, Given J, Hamilton N.Prohibited gene editing in horses (either in embryos or via cell culture and cloning) can result in both desired and undesired outcomes. If left undetected, changes can proliferate within the population in subsequent generations, posing a major threat to welfare and breed integrity.
Naito M, Nishihata S, Amano T.To investigate the factors affecting the utilization of retired Thoroughbred racehorses in equestrian disciplines, Bayesian linear mixed models were separately fitted using rank, round time, and obstacle faults from show-jumping competitions restricted to retired Thoroughbred racehorses as dependent variables, with the interaction between horse sex and the interval from race retirement to competition (as a proxy for transition training to show-jumping) as a fixed effect. When the interval was short (≤1 year), the estimated marginal mean of rank was statistically significantly lower in stalli...
An SJ, Sohn Y, Forbes E, Ryu SH.Osteochondritis dissecans (OCD) is a common developmental orthopedic condition in Thoroughbred racehorses and although arthroscopic surgery is widely used for treatment, its long-term effects on race performance remain unclear. This retrospective study evaluated the effect of OCD surgery on race performance, compared the predictive power of pedigree and management variables and applied interpretable machine learning methods for forecasting race performance outcomes. Data were collected from 75 Thoroughbreds that underwent OCD surgery between 2015 and 2017 and 257 maternal siblings without reco...
Shroff K, Underwood C, Stefanovski D, Hopster K, Slack J.To determine transthoracic impedance (TTI) in adult horses using an exponential biphasic defibrillator and investigate patient and technique factors influencing TTI. Unassigned: A randomized crossover design with 2 phases was used. Phase 1: TTI was measured in dorsal and lateral recumbency, with and without manual pressure on the electrodes in deceased horses immediately following euthanasia. Phase 2: TTI was measured in dorsal recumbency during inspiration and expiration using anesthetized live horses sourced from 2 terminal studies. Mixed-effects linear regression modeling was performed to a...
McDonald C, Cullen S, O'Connor S, Warrington G, Pugh J, McGoldrick A, Nolan C, Losty C.The thoroughbred horse breeding industry contributes significantly to the Irish economy. However, staff shortages threaten the economic sustainability of the industry, as well as the welfare of both horses and workers. Previous research on the staffing crisis faced by the broader horseracing industry has highlighted mental health concerns as a factor. Furthermore, the influence of workplace context on mental health has been widely recognised in organisational psychology. The aim of this study was to assess prevalence rates of Common Mental Disorders (CMDs) in Irish thoroughbred horse breeding ...
Pyles MB, Fowler AL, Crum AD, Hayes SH, Schendel RR, Lawrence LM.Mare milk is the primary source of nutrients for neonatal foals and contains various carbohydrates. Milk oligosaccharides are complex carbohydrates that are resistant to enzymatic digestion and provide support for the immune system and developing microbiome in the neonate. However, factors influencing the synthesis of milk carbohydrates in the mare are not well understood. This study aimed to determine the effects of dietary nonstructural carbohydrate (NSC) on mare milk composition and yield. Thoroughbred mares were paired by age and last breeding date then randomly assigned to one of two diet...
Tobin G, Cullen S, Dunne A, Warrington G, Pugh J, McGoldrick A, Nolan C, Losty C.Stable staff and trainers are essential to racing yards and horse welfare, yet limited research focuses on this vital workforce that the thoroughbred industry heavily relies on. This systematic narrative review synthesizes existing literature on the occupational health and well-being of stable staff and trainers in the thoroughbred horse racing industry. Methods: A systematic narrative review was conducted across PubMed, Google Scholar, and Scopus using relevant keywords. Manuscripts reporting occupational or mental health data on stable staff and/or trainers and had the full-text available we...
Fain H, Hendrickson DA, Buesing MT, Griffenhagen G.Cryptorchidism is a common congenital disorder in male horses characterized by the failure of one or both testes to descend into the scrotum. This developmental anomaly has important clinical, surgical, and economic implications, particularly in breeding animals. This retrospective study investigates the prevalence and laterality of cryptorchidism in a large equine population presented to two veterinary referral hospitals-Colorado State University Veterinary Teaching Hospital (CSU VTH, 1984-2014) and Oakridge Equine Hospital (OEH, 2008-2023). Medical records were reviewed to identify affected ...
Williams JM, Jordan S, Friend L, Kay E, Edmunds M, Flynn H, Wensley S.Horse welfare within/after racing is often questioned by the public. British Racing's Horse Welfare Board's "A life well-lived" strategy provides a blueprint for Thoroughbred welfare, advocating accurate lifetime traceability of horses as essential to achieve this. The Census aimed to establish a population density model for British Thoroughbreds, not actively engaged in racing. Equestrians who owned/kept a Thoroughbred were asked to complete the Census between May and December 2023. Frequency analysis identified patterns in passport compliance, knowledge and understanding of current systems, ...
Joó K, Csanádi L, Povázsai Á, Nielsen MK.Horses remain globally at constant risk of strongylid infections, with cyathostomins being particularly prevalent and abundant. It is essential to routinely monitor the efficacy of anthelmintics against equine nematodes. This study aimed to evaluate the efficacy of ivermectin against equine strongyles and estimate the strongyle egg reappearance period (ERP) following ivermectin treatment for the first time in Hungary. Fecal samples were collected from 57 Thoroughbred mares before treatment and at 2, 4, 5, 6, and 7 weeks post-treatment at a Hungarian National Stud Farm. Fecal egg counts (FECs)...
Legg KA, Cochrane DJ, Gee EK, Chin YY, Rogers CW.Thoroughbred race-riding requires jockeys to attenuate horse movement and maintain postural stability whilst galloping at high speeds. This study aimed to investigate the head movement of jockeys in relation to race-riding experience. Accelerometer and heart rate data were collected from twelve apprentice and two senior jockeys during 85 exercise rides and 82 trial rides. Mean head displacements were determined for each jockey by double integrating the filtered acceleration data. A mixed effect multivariable linear regression model was used to investigate the relationship between jockey experi...
Ebisuda Y, Kitaoka Y, Takahashi Y, Sugiyama F, Yoshida T, Mukai K.Heat acclimation enhances thermoregulation and cardiovascular function. While daily training protocols are typically recommended for humans, optimal training protocols for Thoroughbred horses remain unclear. Here, we compared the effects of two heat acclimation protocols, consecutive and intermittent, in Thoroughbred horses. In a randomized crossover study, eight trained Thoroughbred horses completed either a consecutive (CONS: 9 consecutive days) or an intermittent (INT: 3 days/week for 3 weeks) heat acclimation protocol, comprising 30 min of exercise in hot conditions (WBGT 30°C). Increment...
van Erck-Westergren E, O'Connor S, Stewart BD, Dubois G, Morton J, Hinchcliff KW, Ter Woort F.The frequency, characteristics, and relationship with performance of arrhythmias occurring during high-intensity exercise in Thoroughbred racehorses remain poorly understood. Objective: Describe the frequency, characteristics, and association with subsequent race performance of arrhythmias occurring during intense exercise. Methods: Seventy-one racehorses competing in races sanctioned by the Hong Kong Jockey Club. Methods: Risk-based case-control study. Single-lead ECGs were recorded during high-intensity trials using wearable devices. Ectopic depolarizations identified during warm-up, maximal...
Physical exercise represents a physiological stressor capable of activating the acute-phase response (APR) in horses. However, the relative contribution of exercise intensity duration to acute-phase protein (APP) dynamics remains incompletely defined. This study compared the effects of short, high-intensity gallop exercise (2400 m flat race; = 12) and prolonged, low-intensity endurance exercise (40 km; = 13) on serum amyloid A (SAA), haptoglobin (Hp), and ceruloplasmin (Cp) in Thoroughbred racehorses. Blood samples were collected before exercise and at defined post-exercise time points. Bet...
Putnoki V, Pollard D, Dyson S, Boros K, Nagy A.There are limited data on sequential computed tomographic (CT) evaluation and objective CT assessment of the metacarpal condyles in Thoroughbred racehorses. This longitudinal study aimed to document changes in attenuation of the metacarpal condyles during the first two years of training and racing. Fan-beam CT examination of the metacarpophalangeal regions was performed on 40 non-lame Thoroughbred yearlings, and repeated four more times, approximately six months apart. Mean Hounsfield Unit (HU) measurements were obtained on sagittal reconstructions of the dorsal and palmar halves of the medial...
Pinnell E, Shoemaker S, Wang Y, Tang Y, Sellon D, Leguillette R, Gold J, Sanz M, Bayly WM.Environmental risk factors could contribute to the development of exercise-induced pulmonary hemorrhage (EIPH) in racing Thoroughbreds. Objective: To identify environmental risk factors that might contribute to differences in EIPH prevalence and severity across 12 Thoroughbred racetracks in the United States. Methods: Eight hundred fifteen 2-year-old and 122 >2-year-old Thoroughbred racehorses. Methods: Prospective blinded observational study. Videoendoscopy was performed 30-60 min post-race. Three observers independently assigned an EIPH grade to each videorecording, and prevalence and sever...
