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.
The proposed biological mechanisms for exercise-induced pulmonary haemorrhage (EIPH) are many and varied. Better knowledge of risk factors should lead to achievable measures to reduce the incidence. Objective: To identify risk factors associated with epistaxis following racing in UK Thoroughbreds, to gain possible insights into the pathogenesis of the condition and to investigate the association between epistaxis and race finishing position. Methods: The association of epistaxis occurring on UK racecourses between 1996 and 1998 with a wide range of race-, horse- and start-level variables was e...
A 4-month-old Thoroughbred filly presented for abdominal pain was diagnosed with a T-shaped malformation of the ventral colon at exploratory laparotomy. Following resection and anastomosis of the large colon, no further episodes of abdominal pain occurred during a 12-month follow-up. Acute dehiscence of the linea alba occurred as a complication of the initial laparotomy, but was successfully managed following additional surgical repair. T-shaped malformation of the ventral colon has not previously been reported and is considered a congenital malformation of mesocolon formation.
Within the veterinary world, data regarding the surgical management of hypospadias is lacking. Reports within equines have documented resective phallectomy procedures rather than urethral reconstruction. This case report documents the first ever urethroplasty for an equine hypospadias, performed by a consultant paediatric surgeon. The urethroplasty was achieved by applying the same surgical principles mastered from paediatric urology to a horse. The indication for surgery was contact dermatitis of the hind-leg, which impaired the thoroughbred foal's racing potential. Methods: A single stage ur...
Osteochondrosis (OC) develops in growing horses due to disturbed differentiation and maturation of cartilage, particularly at the predilection sites of the fetlock, hock and stifle joints. Horses with osteochondrotic lesions are at a high risk of developing orthopaedic problems later in life. This article briefly reviews the published heritability estimates for OC and offers perspectives for selection in the horse industry. Heritabilities for OC in Warmblood and Standardbred horses have been estimated at 0.1-0.4 in animal threshold models. Whole genome scans using microsatellites have identifi...
To determine risk factors for Clostridium piliforme infection in neonatal foals on a Thoroughbred breeding farm in California. Methods: Case-control and retrospective cohort studies. Methods: 322 neonatal Thoroughbred foals either born on the study farm or born elsewhere but traveled to the farm with their dam during the 1998, 1999, and 2000 breeding seasons. Methods: Mare and foal records from 1998, 1999, and 2000 were examined, using case-control design methods to determine variables associated with increased risk of C. piliforme infection in foals. Important risk factors identified in the c...
Serum anti-Müllerian hormone (AMH), a marker of equine cryptorchidism, is detectable in intact and cryptorchid stallions but not in geldings because it is secreted from Sertoli cells. A 4-year-old uncastrated Thoroughbred racehorse had no visible testes; therefore, the horse was considered a bilateral cryptorchidism. However, the serum AMH was undetectable (<0.08 ng/ml). Human chorionic gonadotrophin (hCG) stimulating test result indicated that the horse was a gelding. The results of sex chromosomal analysis and sequence analysis of SRY gene suggested that the horse was a genetically-intac...
A breed known for its versatility, the American Quarter Horse (QH), is increasingly bred for performance in specific disciplines. The impact of selective breeding on the diversity and structure of the QH breed was evaluated using pedigree analysis and genome-wide SNP data from horses representing 6 performance groups (halter, western pleasure, reining, working cow, cutting, and racing). Genotype data (36 037 single nucleotide polymorphisms [SNPs]) from 36 Thoroughbreds were also evaluated with those from the 132 performing QHs to evaluate the Thoroughbred's influence on QH diversity. Results s...
Scott D, Kreitner K, Kim L, Seabaugh K, Duncan C, Magzamen S.To characterize spatiotemporal patterns of criteria air pollutants surrounding Thoroughbred racetracks in the US. Unassigned: We identified all active Thoroughbred racetracks from 2011 through 2024, linking their location with daily air quality data from the US Environmental Protection Agency (EPA) Air Quality System. Mean daily and annual pollutant concentrations within a 50-km bounding box of each racetrack were summarized using descriptive statistics and evaluated for monthly and annual trends. Exceedances were defined as any observation in which pollutant concentration met or exceeded the ...
Brown NL, Irandoust S, Thom EJ, Whitton RC, Henak CR, Muir P.Condylar stress fracture of the third metacarpal bone (MC3) is a common catastrophic injury in Thoroughbred racehorses and is associated with parasagittal groove (PSG) subchondral osteolysis. Standing computed tomography (sCT) imaging enables sensitive identification of this fatigue-induced early subchondral bone injury (SBI), but there is no objective method for identifying racehorses at heightened risk of condylar stress fracture. Objective: To estimate PSG first principal strain in elite Thoroughbred racehorses that have undergone subjective risk assessment using sCT fetlock screening. Meth...
Furukawa R, Tozaki T, Kawate K, Kikuchi M, Ishige T, Fukui E, Kakoi H.A subset of single-nucleotide polymorphisms (SNPs) are associated with various phenotypes, including diseases, coat colour, and athletic performance, and are widely used in medical and veterinary fields. In this study, we developed a novel method for direct SNP genotyping from whole blood without DNA extraction. Thoroughbred blood samples were diluted 100-fold with Milli-Q water and analysed using real-time polymerase chain reaction (PCR) with hydrolysis probes. Specificity and sensitivity were improved by increasing the annealing temperature and number of PCR cycles. Genotyping results for SN...
Faramarzi B, Lee D, Khamas W, Dong F.The distal sesamoidean impar ligament (DSIL) is a key component of the equine podotrochlear apparatus, yet its role in conditions such as caudal heel pain and navicular syndrome remains poorly understood. The objective of this study was to characterize the histological properties of the DSIL and evaluate how it is influenced by breed and age. Eighty-four cadaveric forelimb DSIL samples were collected from young, athletic Quarter horses (QHs), Thoroughbreds (TBs), and older, retired Quarter horses. Samples were stained and assessed for vessel size and count, number of nerve fascicles, and the r...
Navas de Solis C, Durando M, Nath L, Durward-Akhurst S.Exercise associated sudden death (EASD), defined as a fatal collapse in a closely monitored and previously presumed clinically healthy horse that occurs during exercise or within approximately 1 h after exercise, is disproportionately more common in equine than in human athletes. Objective: To describe ECGs from EASD cases in Thoroughbred racehorses. Methods: Retrospective case series. Methods: An international call for potential cases was made through direct contact with relevant racing authorities requesting that trainers of horses which had experienced EASD consent to researchers gaining ac...
Suzuki T, Kato F, Yamaga T, Tagami M, Tagami M.Complete atrioventricular septal defect (AVSD) is rarely reported in horses. We retrospectively reviewed three Thoroughbred foals (2017-2023) with necropsy-confirmed complete AVSD and summarized their clinical presentation, transthoracic echocardiographic findings, and postmortem anatomy. All foals showed early signs of congenital cardiac disease including weakness, failure to thrive and cardiac murmurs. Echocardiography demonstrated a common atrioventricular junction with a single atrioventricular valve and combined atrial and ventricular septal defects; all were classified as Rastelli type C...
Li K, Cappelletti E, Dessaix C, Ciosek J, Robyn E, Johnson L, AbouEl Ela NH, Arias X, Adelson DL, Raudsepp T, Piras FM, Laird-Smith M, Hudson E....We present telomere-to-telomere genome assemblies of a Thoroughbred horse and a donkey derived from their mule offspring. Now adopted and annotated by NCBI as reference genomes, these assemblies resolve previously inaccessible regions, including satellite arrays, duplications, and telomeres. Equids are known to exhibit an uncoupling between satellite DNA and centromeric function. The completeness of these assemblies enabled annotation of both satellite-based and satellite-free centromeres, as well as non-centromeric satellite loci, revealing notable centromeric plasticity. They also allowed de...
Petersen JL, Finno CJ.A prior genome-wide association (GWA; N = 200) including Thoroughbreds and stock horses implicated chromosome 6 (NC_009149.3) in owner-reported equine anhidrosis. A missense variant in KCNE4 (NC_009149.3:g.11813731A>G) was proposed as a risk allele, although its association with anhidrosis was not reported. Variant annotation and protein modelling in the original study suggested the G allele conferred risk. We reported no association of the G allele with anhidrosis in 50 horses phenotyped by an intradermal terbutaline sweat test (ITST); all horses produced sweat regardless of genotype. ...
Dirikolu L, Liu CC, Schaeffer DJ.The objectives of the study were to report the incidence of race-related injuries and equine fatalities in racehorses at the Louisiana racetracks from 2014 to 2022 for both Thoroughbred and Quarter Horse racehorses. Additionally, this study evaluated several factors that may be related to the occurrence of race-related injuries in racehorses in Louisiana. The average rates of equine fatal injuries (euthanized on or off track within 72 h of the race) were 1.70 ± 0.76 and 1.94 ± 0.89 per 1000 starts in Thoroughbred and Quarter racehorses, respectively. The average rates of non-fatal injur...
