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.
Milne FJ.FOR MANY YEARS, concern has been expressed at the wastage of young Thoroughbreds at the racetrack. This concern even manifested itself in the publication of a book (1) which referred to the prevailing practice of prematurely start-ing the racing career of the Thoroughbred long before it had attained sufficient maturity to engage in stiff, damaging competition. This is not a fault of the Thoroughbred industry alone, because in certain parts of the U.S.A., Quarter Horses less than two years of age are already racing. We could swing to the opposite extreme, of course, to the pleasure horse world ...
Witherington DH.The post-race heart rates have been recorded in 1,000 Thoroughbreds following Flat, Hurdle and Steeplechase races in varying climatic conditions and on 54 different British racecourses. The post-race deceleration of the heart rate, under racecourse conditions, was marked by an apparent three-phase recovery period. Reference is made to the normal heart sounds and to the relationship between the heart and respiratory rates.
Baird JD, Hutchins DR, Lepherd EE.A 12-month-old thoroughbred horse, after being treated with 30 g. of micronized phenothiazine, developed an acute haemolytic anaemia characterized by Heinz-body formation. Elevation of serum glutamic oxaloacetic transaminase, isocitric dehydrogenase, lactate dehydrogenase and blood urea nitrogen also occurred. The colt's clinical condition improved after receiving blood transfusions, fluids, antibiotics and corticosteroids. After 10 weeks, the haematological and biochemical picture returned to normal. [A.S.] D.A.Cz.
Son JK, De Paz P, Kim J, Sanaei R, Seungho R, Bailey S, Davies HMS.The risk of carpal injury in racehorses may be related to the morphology, yet whether carpal morphologies are set from birth or change through growth remains unclear. Objective: To quantify carpal bone changes through growth. Methods: Twenty privately owned Thoroughbred foals born between January 2022 and May 2023 were radiographed bimonthly from birth to 10 months of age. Imprint training was used to take radiographs safely without chemical restraints. Fifteen individual and 11 relative angular carpal parameters were measured using ImageJ on dorsopalmar radiographs of the carpus at zero degre...
Takahashi K, Mukai K, Ebisuda Y, Sugiyama F, Yoshida T, Hatta H, Kitaoka Y.Evidence suggests that positive pacing strategy improves exercise performance and fatigue tolerance in athletic events lasting 1-5 min. This study investigated muscle metabolic responses to positive and negative pacing strategies in Thoroughbred horses. Eight Thoroughbred horses performed 2 min treadmill running using positive (1 min at 110% maximal O uptake [V̇Omax], followed by 1 min at 90% V̇Omax) and negative (1 min at 90% V̇Omax, followed by 1 min at 110% V̇Omax) pacing strategies. The arterial-mixed venous O difference did not significantly differ between the two strategies. Pl...
Flores JG, Bueno VC, Bastos HBA, Rechsteiner SMDEF.Reproductive biotechniques in the equine species have advanced in the last decade and horse breeders have started to question the possibilities of interfering in the determination of foal sex. The aim of the present study was to verify whether the variables mares and stallion's age, side of the ovary containing the preovulatory follicle, preovulatory follicle diameter, time between breeding and ovulation, and ovulation inducing hormones influence the sex of the foal. A total of 259 reproductive cycles of 160 mares and 22 Thoroughbred stallions were used. Statistical analysis was performed usin...
Stutsel M, Jordan L, Smith C, Lee WY, Symonds N, Bell R, Young A.Foot-related lameness is common in Standardbred and Thoroughbred racehorses. Magnetic resonance imaging (MRI) provides information on both the soft tissue and osseous structures of the distal extremity. The aim of this study was to determine whether abnormalities identified on distal limb MRI differed between these two racehorse populations. Methods: The records of Standardbred and Thoroughbred racehorse distal extremity MRI examinations conducted at Camden Equine Centre and Ballarat Veterinary Practice between 2013 and 2023 were retrieved. Horses were included if pain causing lameness had bee...
Cheung HW, Wong KS, Tam JCL, Farrington AF, Bond AJ, Wan TSM, Ho ENM.Erythropoiesis-stimulating agents (ESAs) continue to be a significant threat to the integrity of human and equine sports. Besides conventional direct testing, monitoring the biomarkers associated with the effects of ESAs may provide a complementary approach via indirect detection to enhance doping control. In this study, we applied label-free proteomics to discover plasma protein biomarkers in Thoroughbred geldings after administration with a long-acting form of recombinant human erythropoietin (rhEPO), methoxy polyethylene glycol epoetin beta, Mircera. Increased haematocrit, haemoglobin and r...
Cassiers V, McNally T.Palatal dysfunction (PD), which encompasses palatal instability (PI) and intermittent dorsal displacement of the soft palate, is the most common performance-limiting upper respiratory tract obstruction in young Thoroughbred racehorses. Soft palate thermocautery (SPT) performed under general anaesthesia is a routinely performed procedure for PD in some countries, but the procedure for and outcome of SPT performed under standing sedation has not been published. (1) To describe a technique for SPT performed under standing sedation; and (2) to assess post-operative performance in horses compared t...
Kuroda T, Minamijima Y, Kinman CK, Takahashi Y, Ebisuda Y, Inoue K, Ishikawa H, Mita H, Tamura N, Nukada T, Toutain PL, Ohta M.Quinidine (QND) sulfate is an effective treatment for atrial fibrillation (AF) in horses, and several dosage regimens have been proposed to address its wide variability in response and potential adverse effects. The purpose of this study was to analyze the variability in plasma quinidine concentrations using population pharmacokinetics to determine an effective and safe dosage regimen for Thoroughbred horses. Unassigned: Six healthy Thoroughbred horses were treated with 20 mg/kg quinidine sulfate dihydrate (16.58 mg/kg QND base) administered PO or 5 mg/kg quinidine hydrochloride monohydr...
Argue BJ, Ahern BJ.The veterinary yearling pre-sale repository radiographs have the potential to impact both vendor and prospective purchaser. The primary aim of this study was to determine inter-observer agreement for orthopaedic lesions identified in thoroughbred yearling repository radiographs. A secondary goal was to determine agreement when using a pre-defined risk rating classification. Unassigned: Three experienced specialist equine surgeons (2 ACVS & 1 FANZCVS) interpreted thirty repository radiographs once each for radiographic abnormalities. Each radiographic abnormality was given an associated ris...
Nomura M, Kuroda T, Ohta M, Kusano K, Minamijima Y, Nagata S.Salbutamol is a short-acting and selective beta-2 adrenergic agonist. Inhaled (IH) administration of salbutamol is widely used to control lower respiratory tract disease in horses. Here, we estimated the pharmacokinetic parameters of salbutamol after a single intravenous (IV) or IH administration in six horses, and we statistically analysed the detection times with various dosing regimens. Plasma and urine concentrations of salbutamol were measured by liquid chromatography-tandem mass spectrometry, and data were modelled by using a nonlinear mixed effect model followed by Monte Carlo simulatio...
Ryu SH, Lee KE, Forbes E, An SJ, Kim JG, Lee H, Kim BS.Equine behavioral traits are important criteria to assess the suitability of retired Thoroughbred racehorses for equestrian sports. Objective: This study aims to develop a practical procedure to assess retired Thoroughbreds for their suitability for equestrian sports or leisure purposes and to assess if horses identified as having reactive temperaments in response to a standardized startle test, will have improved test results following a period of transition training. Methods: Behavioral reactivity data and cardiac autonomic responses to a startle test (comprising of a plastic bag applied to ...
Davis MS, Bayly WM, Hansen CM, Barrett MR, Blake CA.The intracellular environment of skeletal muscle can develop pronounced hyperthermia and acidosis during strenuous exercise, and these alterations in the typical intracellular conditions have been shown to alter mitochondrial respiration. However, the impact of these conditions on ATP synthesis is poorly understood. We used Thoroughbred racehorses to test the hypothesis that both hyperthermia and acidosis decrease the rate of ATP synthesis, but that athletic conditioning mitigates this loss of phosphorylation capacity. Isolated mitochondria were harvested from skeletal muscle before and after ...
Norton AM, Rosanowski SM, O'Brien T.Epiglottic entrapment (EE) is a common cause of poor performance in racing standardbreds (STBs) and thoroughbreds (TBs). There is limited information published on the condition in STB racehorses and limited information on factors associated with return to racing available for either breed. Unassigned: This study investigated and compared the pre surgical findings, post-surgical complications and racing performance in STBs and TBs undergoing surgery for correction of EE. Associations between signalment and pre-surgical findings, and the presence of complications and racing post-surgery were com...
Allen SE, Taylor S, Given J, Verheyen KL.The British horseracing industry is committed to reducing equine fatalities in jump racing. Race-related fatalities are a major welfare concern and threaten the sport's social licence to operate. Objective: To describe the risk of, and determine risk factors for, fatality in British jump racing. Methods: Retrospective cohort. Methods: Analyses included all starts made in British jump races between January 2010 and April 2023. Available information for each horse, race, racecourse, trainer and jockey was collated and combined with details of all fatalities recorded by official veterinary office...
Silva GC, Nogueira CEW, Scalco R, Pizzi GLBL, Leite TA, Bastos R, Curcio BR.Gestation length (GL) in horses varies widely, influenced by multiple variables, including maternal, fetal, and environmental factors. This study aimed to investigate and quantify the relative contributions of climatic (photoperiod and temperature-humidity index - [THI]), maternal (age and parity), fetal (sex) and environmental (year and month of foaling) variables influencing gestation length in Thoroughbred mares. Retrospective data encompassing 704 pregnancies across nine breeding seasons in tropical and subtropical Brazilian climates were analyzed. Stepwise regression analysis identified f...
McGivney CL, McGivney BA, Farries G, Gough KF, Han H, Holtby AR, MacHugh DE, Katz LM, Hill EW.Equine recurrent laryngeal neuropathy (RLN) is an economically important upper respiratory tract (URT) disease with a genetic contribution to risk, but genetic variants independent of height have not been identified for Thoroughbreds. The method of clinical assessment for RLN is critical to accurately phenotype groups for genetic studies. Objective: To identify genetic risk loci for RLN in Thoroughbreds in a genome-wide association study (GWAS) following high-resolution phenotyping. Methods: Case-control. Methods: Thoroughbred horses were characterised as RLN cases and controls using resting a...
Yildirim İG, Karaarslan S, Erkan A.Musculoskeletal injuries (MSI) are a major concern in the horse racing industry, often leading to career-ending outcomes. Contributing factors include conformation, limb and joint defects, hoof structure, age, and hard track surfaces. Objective: This study aimed to evaluate the distribution of MSI in Thoroughbred and Arabian racehorses during racing and training, categorised by breed and track surface. Methods: Retrospective cohort study. Methods: The data from 2018 to 2023 were collected at the Turkish Jockey Club's Şirinyer Hippodrome (38°23'03.7″ N 27°09'01.0″ E), covering 553 MSI ca...
Gallacher K, Champion K, Denholm KS.Foals suffer from total failure to transfer passive immunity (TFTPI) when serum immunoglobulin (IgG) is <4 g/L, and partial failure to transfer passive immunity (PFTPI) when serum IgG is 4-8 g/L. Objective: To explore risk factors for poor serum IgG concentration. Methods: Retrospective observational study. Methods: Data from 535 Thoroughbred foals born to 177 mares were analysed and included foal sex, birthweight, month and year of birth and colostrum Brix %. Associations between dam age and colostrum Brix (%); and between foal serum IgG and liveweight gains were also measured. Pre-suckle...
Ha Y, Yi K, Park C, Kim G, Choi D, Lee J, Kim N.This study aimed to measure the whole blood viscosity (WBV) in racehorses using a new viscometer and establish reference values, as well as to investigate the correlation between the WBV and the haematological parameters and serum chemistry. WBV measurements were conducted on 51 Thoroughbred horses using a novel U-shaped scanning capillary-tube viscometer. The reference values for the WBV were determined at various shear rates ranging from 1 s to 1 000 s. Correlation analyses were performed to examine the correlation between the WBV and the haematological and serum chemistry parameters. The fi...
Orozco Lopez D, Garcia-Lopez JM, Carpenter R, Bras JJ, Richardson DW, Ortved KF.To describe the outcome of metacarpophalangeal (MCPJ) and proximal interphalangeal joint (PIPJ) arthrodesis using a locking compression-distal femur plate (LCP-DFP) in Thoroughbred racehorses with traumatic disruption of the suspensory apparatus (TDSA) at risk of PIPJ subluxation. Methods: Multicenter retrospective study. Methods: Twenty-six Thoroughbred racehorses. Methods: Records of Thoroughbred racehorses with TDSA that had undergone MCPJ and PIPJ arthrodesis using an LCP-DFP at three referral hospitals between 2020 and 2024 were reviewed for inclusion. The preoperative data collected incl...
Dollemore G, McGovern K, Tallon R.Conservative and surgical management of left dorsal displacement and nephrosplenic ligament entrapment of the large colon (NSLE) is well described in horses. Whilst breed factors predispose the development of NSLE, it is unknown if breed affects the likelihood for surgical intervention. Objective: To compare the incidence of surgical intervention and differences in pre-operative parameters between Thoroughbred and non-Thoroughbred horses. The authors hypothesise a higher proportion of Thoroughbreds require surgical intervention. Methods: Retrospective cross-sectional study. Methods: Case recor...
Heath HD, Peng S, Szmatola T, Ryan S, Bellone RR, Kalbfleisch T, Petersen JL, Finno CJ.Allele-specific expression (ASE) analysis provides a nuanced view of cis-regulatory mechanisms affecting gene expression. Results: An equine ASE analysis was performed, using integrated Iso-seq and short-read RNA sequencing data from four healthy Thoroughbreds (2 mares and 2 stallions) across 9 tissues from the Functional Annotation of Animal Genomes (FAANG) project. Allele expression was quantified by haplotypes from long-read data, with 42,900 allele expression events compared. Within these events, 635 (1.48%) demonstrated ASE, with liver tissue containing the highest proportion. Genetic var...
Chatha MA, Ahmad N, Abbas MA, Saadullah M, Khan JA.This study was designed to explore the impact of intrinsic (breed of foal, age of dam, and age of foal at weaning) and extrinsic (season of birth and housing type) factors on the growth and survival of foals in the subtropical conditions of Pakistan. For the growth study, retrospective data analysis of foals (n = 150) born from purebred brood mares of Thoroughbred, Arabs, and Percheron breeds (n1, n2, and n3 = 50 each) was made. Six hundred and twenty-four (n = 624) foals born between 2020 to 2022 were observed for the study of foal survival rate. The survival of these foals till the age of on...
Klitzing L, Kirsch K, Schindler M, Merle R, Hoffmann G, Thöne-Reineke C, Wiegard M.The novel object test is one of the three most common fear tests in veterinary science and employed in several different species. Although having been applied in several different studies in horses, it is surprising that there is no standardized test procedure available for these kinds of tests. Unassigned: This study investigated the performance of the novel object test on 42 young Thoroughbred horses to determine the effect of sex (mare or stallion), test sites (round pen or paddock) and whether the horses had previously participated in an auction or not on the behavior during the novel obje...
Wilson CS, Carrick J, Shearer P, Heller J, Brookes VJ.Pregnancy failure is a serious economic and welfare concern in the Thoroughbred horse industry, yet its incidence and risk factors in Australia remain unclear. This retrospective, nested, case-control study investigated pregnancy failure in resident mares on studs in the Hunter Valley, Australia, in 2021-2022, in early (46-150 days), mid (151-270 days), and late (>270 days) gestation. We found an annual incidence risk of 5.4 pregnancy failure cases/100 45-day pregnancies (0.05 cases/mare; 95 % CI 0.04-0.07), with full-term (perinatal) losses (≥320 days) accounting for 24 % of cases (9...
Barshick MR, Ely KM, Mogge KC, Chance LM, Johnson SE.Methylsulfonylmethane (MSM) is a sulfur-containing molecule with reported anti-inflammatory and antioxidant activities. Exercise causes the formation of free radicals and stimulates inflammatory gene expression in leukocytes and skeletal muscle. The hypothesis that dietary supplementation with MSM alters the exercise-mediated inflammatory and oxidant response was assessed in unfit adult thoroughbred geldings. Ten geldings (6.7 ± 1.6 yr) were assigned to a diet supplemented without (CON, = 5) or with 21 g of MSM ( = 5) for 30 days. Following the supplementation period, horses performed a stan...
Kodaira K, Kakizaki M, Nagata SI, Ode H, Okano A, Tamura N, Mizobe F, Matsuda Y, Kurimoto S, Aida H.To investigate the pharmacodynamics and pharmacokinetics of rocuronium administered by bolus injection to sevoflurane-anesthetized horses. Methods: Prospective, experimental, crossover study. Methods: Five healthy adult Thoroughbred horses (body mass 368-470 kg, three females and two males). Methods: Each horse was anesthetized twice with sevoflurane and assigned to be administered rocuronium bromide intravenously: 0.2 mg kg (R02) or 0.4 mg kg (R04). There was a minimum 2 week washout period between experiments. During anesthesia, the peroneal nerve was stimulated (train-of-four) and neuromusc...
Hardwick JL, Ahern BJ, Crawford KL, Allen KJ, Anderson BH, Rose KJ, Franklin SH.The relationship between Thoroughbred yearling laryngeal function (YLF) grade and race performance is unclear. Objective: To determine the effect of YLF on future race performance. Methods: Retrospective cohort study. Methods: Post-sale endoscopic recordings were reviewed from Australian yearling sales in 2018-2019. Race performance was evaluated for career and as 2-, 3- and ≥4-year-olds. Multivariable generalised linear modelling examined the association between YLF and performance, with risk estimates presented as coefficients (95% CI). Results: The YLF in 5175 examinations was graded I in...
Harding C, Viljanto M, Hincks P, Habershon-Butcher J, Paine SW.Omeprazole is a gastric acid secretion inhibitor used as an effective anti-ulcer drug. Based on oral administration studies, its International Screening Limit (ISL) was established in plasma and urine at 1 ng/mL with a Detection Time (DT) of 48 h. A novel formulation of injectable omeprazole has since been released, and therefore, a pharmacokinetic study was performed to assess the DT above the ISL against current advice. Six Thoroughbred horses were given four repeated weekly intramuscular administrations of omeprazole (4 mg/kg). Plasma and urine omeprazole concentrations were measured ...
Sanz MG, Jellen G, Cody L, Bergsma J, Cha M, Kogan C, Kordas G, Bayly WM, Leguillette R.Mild-moderate asthma is common in horses. Inhaled ciclesonide has been approved only for treatment of severe asthma in horses. Objective: We hypothesized that a 10-day treatment course of inhaled ciclesonide (Aservo EquiHaler) would improve clinical signs, endoscopic tracheal mucus scores, and bronchoalveolar lavage fluid (BALF) cytology in racehorses with moderate asthma. Methods: Racehorses with moderate asthma housed at the Emerald Downs Racetrack in Auburn, WA. Methods: Prospective, randomized, double-blinded, placebo-controlled clinical study. Horses received inhaled ciclesonide (n = ...
Son JK, De Paz P, Kim J, Sanaei R, Ryu S, Bailey S, Davies HMS.Changes in the third metacarpal (MC3) mid-diaphyseal dimensions were measured radiographically in young Thoroughbred racehorses through race training and found to be associated with a higher risk of shin soreness. However, it is still unclear whether such negative MC3 morphologies are set congenitally or through development. Objective: To quantify MC3 bone dimensional changes through growth. Methods: Longitudinal. Methods: Twenty privately owned Thoroughbred foals were radiographed bimonthly from birth to 14 months of age. Four linear MC3 parameters (proximodistal MC3 length, mid-diaphyseal do...
