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.
Ivester KM, Couëtil LL, Moore GE.Mild equine asthma is presumed to arise in response to environmental exposures but the relative impact of differing inflammatory phenotypes upon performance are largely unexplored. Objective: Airway inflammation negatively affects performance and cytological phenotype varies with environmental exposure. Methods: Thoroughbred racehorses in active training and racing. Methods: Thoroughbreds were recruited 24-48 hours before racing. Each horse was eligible for re-enrollment with each race entry. Within one hour of race completion, physical examination, respiratory endoscopy, and BAL were performe...
Muko R, Sunouchi T, Urayama S, Toishi Y, Kusano K, Sato H, Muranaka M, Shin T, Oikawa MA, Ojima Y, Ali M, Nomura Y, Matsuda H, Tanaka A.Histidine-rich glycoprotein (HRG) is abundant plasma protein with various effects on angiogenesis, coagulation, and immune responses. Previously, we identified the base and amino acid sequences of equine HRG (eHRG) and revealed that eHRG regulates neutrophil functions. In this study, we first conducted a large-scale gene analysis with DNA samples extracted from 1700 Thoroughbred horses and identified unique insertion/deletion polymorphisms in the histidine-rich region (HRR) of eHRG. Here we report two types of polymorphisms (deletion type 1 [D1] and deletion type 2 [D2]) containing either a 45...
Whitton RC, Rose RJ.To determine the frequency of damage to the medial palmar intercarpal ligament (MPICL), and the range of sizes of the dorsomedial intercarpal ligament (DMICL) of the midcarpal joint in horses with no history of carpal joint disease. Methods: Cadaver limbs were collected from 72 horses with no history of carpal joint disease. One hundred and forty-two midcarpal joints were dissected and the MPICL and DMICL were examined. Measurements were made with a digital micrometer. Results: MPICL tearing was present in 88 of 96 joints from horses 2 years and older. Tears were predominantly of the dorsolate...
Brandon RB, Giffard JM, Bell K.Single nucleotide polymorphisms (SNPs) in exons 13, 15 and 16 of equine transferrin for common, rare and mutant variants were investigated. Compared with previous work a further 13 SNPs have been identified, allowing for the two previously identified clades to be subdivided into 11 groups. A combination of one or more of eight SNPs can be used to classify the equine variants into these 11 groups, since most are co-inherited. Putative sites of glycosylation in exons 13 and 16 showed no polymorphism, suggesting that presence or absence of sugar moieties does not lead to electrophoretic variation...
Kingston JK, Bayly WM, Sides RH.Exercise-induced pulmonary haemorrhage has been associated with reduced performance in racing horses. However, it is unclear what volume of blood loss into the lungs impairs performance. The purpose of the present study was to determine the minimal volume of autologous Horses blood instilled into the airways that significantly affects performance and pulmonary function in exercising horses. Six Thoroughbred horses performed 2 exercise bouts on each of 4 treatment test days. Each exercise bout consisted of a 2 min warm-up at 4 m/s followed by running at a speed equivalent to 115% VO2max, until ...
Lyons ET, Bolin DC, Bryant UK, Cassone LM, Jackson CB, Janes JG, Kennedy LA, Loynachan AT, Boll KR, Burkhardt AS, Langlois EL, Minnis SM, Welsh SC....Parasite infections are more quantifiable postmortem than antemortem in horses. Thus a study was carried out examining dead horses for specific parasite species. Most of the weanling and older horses submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) for postmortem examination between November 22, 2016 and March 23, 2017 were examined for certain species of internal parasites. The stomach and duodenum from 69 horses were examined for bots (Gasterophilus spp.). Combined data for both Thoroughbred and non-Thoroughbred (16 other than Thoroughbred breeds/mixed breeds)...
Choi TLS, Wong JKY, Kwok WH, Curl P, Mechie S, Wan TSM.Methylstenbolone (2,17α-dimethyl-5α-androst-1-en-17β-ol-3-one) is a synthetic anabolic and androgenic steroid (AAS) sold as an oral 'nutritional supplement' under the brand names 'Ultradrol', 'M-Sten' and 'Methyl-Sten'. Like other AASs, methylstenbolone is a prohibited substance in both human and equine sports. This paper describes the studies of the in vitro and in vivo metabolism of methylstenbolone in horses using LC/HRMS, GC/MS and GC/MS/MS. Phase I in vitro metabolic study of methylstenbolone was performed using homogenised horse liver. Hydroxylation was the only biotransformation obse...
Davies Morel MC, Newcombe JR, Hinchliffe J.Delayed uterine involution is a major cause of early reproductive failure in mares. Involution is affected by mare age, and foaling to covering interval. Involution rates vary between the previously non-gravid horn (PNGH), which recovers the quicker, and the previously gravid horn (PGH). Location of a pregnancy and its likely success may, therefore, be affected by its location relative to the previous pregnancy. This study aimed to determine: (i) the location of concepti in consecutive pregnancies; (ii) whether this varies with mare age or foaling to conception interval; (iii) whether location...
Byron CR, Benson BM, Karlin WM, Stewart AA.To report the use of a proximolateral endoscopic portal with a distolateral instrument portal for carpal retinaculum release in a horse clinically affected with carpal canal syndrome. Methods: Clinical report. Methods: A 4-year-old Thoroughbred female. Methods: Carpal canal syndrome secondary to traumatic suppurative tenosynovitis was treated by accessory carpal bone debridement and carpal retinaculum release using a tenoscopic approach to the carpal flexor synovial sheath through a proximolateral endoscope portal and a distolateral instrument portal. Results: Resolution of carpal sheath effus...
Bailey CJ, Reid SW, Hodgson DR, Rose RJ.A prospective study of injuries and disease in a cohort of Australian thoroughbreds in training was conducted with the participation of 24 trainers. From the horses catalogued at a major yearling sale in 1995, 169 were enrolled in the study and followed through their two- and three-year-old racing seasons. The principal aim was to quantify the time lost in training as a result of the various categories of injuries and disease, recorded as either days of modified training, or weeks rested at pasture. Shin soreness was the most common condition in two-year-olds (affecting 42 per cent of the hors...
Davies HM.The third metacarpal bones (MC3) of racing Thoroughbreds are a common site for bone damage. The midshaft dorsal cortex (DC) of MC3 thickens in response to fast exercise. It is not clear if it changes to a shape and size that limits the peak bone strains to a range associated with normal loading in other species. Objective: To relate the proportionate size of the DC cortex in racehorses exercising at racing speed to surface strains, and test whether the DC reached a plateau that was sustained through subsequent exposures to racing speed exercise. Methods: Standardised lateral MC3 radiographs we...
Takahashi T, Yoshihara E, Mukai K, Ohmura H, Hiraga A.Although the main cause of injury to the superficial digital flexor tendon (SDFT) is assumed to be high intensity loading of the tendon, to date the forces exerted on the SDFT during cantering have never been measured. Objective: To measure the force exerted on the SDFT at walk, trot and canter on a treadmill. Methods: Arthroscopically implantable force probes (AIFP) were implanted in the SDFT of the left and right forelimbs of 8 Thoroughbred horses (480-565 kg). The output of the AIFP was calibrated using the SDFT force calculated by inverse dynamics and an in vitro model of the lower forelim...
Riond B, Wenger-Riggenbach B, Hofmann-Lehmann R, Lutz H.Serum protein electrophoresis is a useful screening test in equine laboratory medicine. The method can provide valuable information about changes in the concentrations of albumin and alpha-, beta-, and gamma-globulins and thereby help characterize dysproteinemias in equine patients. Reference values for horses using agarose gel as a support medium have not been reported. Objective: The purpose of this study was to establish reference intervals for serum protein concentrations in adult horses using agarose gel electrophoresis and to assess differences between warm-blooded and heavy draught hors...
Yang YH, Kim KI, Cothran EG, Flannery AR.We used sequence polymorphism of the mitochondrial DNA D-loop (968 bp excluding the tandem repeat region) to determine genetic diversity of horses inhabiting Cheju (a southern island of Korea). Seventeen haplotypes with frequencies from 1.5 to 21.5% were found among 65 Cheju horse samples. Genetic diversity (h) of the 17 haplotypes was calculated to be 0.91, indicating that the extant Cheju horse population consists of diverse genetic groups in their maternal lineage. Phylogenetic analysis showed that 17 types of Cheju (D-loop sequences determined), 5 Mongolian, 6 Arabian, 3 Belgian, 2 Tsushim...
Elcombe ME, Bellone RR, Magdesian KG, Finno CJ.Equine familial isolated hypoparathyroidism (EFIH) and fragile foal syndrome (FFS) are both fatal recessive conditions reported in Thoroughbred foals. The causal variants for EFIH (RAPGEF5 c.2624C>A; EquCab3.0. chr4: g.54108297G>T) and FFS (PLOD1 c.2032G>A; EquCab3.0, chr2: g.39927817) were recently reported. Prevalence assessment for these variants in a large cohort of samples is needed to provide evidence-based recommendations for genetic testing. Objective: To estimate the frequency of the EFIH and FFS variant alleles in the United States Thoroughbred population between 1988 and 20...
Flash ML, Crabb HK, Hitchens PL, Firestone SM, Stevenson MA, Gilkerson JR.The number of horses leaving the Australian Thoroughbred (TB) racing industry each year is of concern to animal welfare advocates, public and regulators. A horse's previous athletic performance is a significant driver of retirement from racing. Racehorse performance can be measured in terms of the total number of starts, duration of racing and prize money earned. This study investigated Australian racing records for the 2005 and 2010 Victorian TB foal crops to identify factors associated with total number of starts, racing career duration, prize money earned and age of last race start-up to th...
Robert C, Valette JP, Denoix JM.There is limited published data on conformational changes in the forelimbs of growing foals. This study was designed to describe the changes in conformation of the carpus and distal forelimb from birth to weaning in foals of three different breeds. Evaluation of the conformation of the carpus, fetlock, pastern and foot was carried out in 134 Thoroughbreds, 162 French Trotters and 98 Selle Français (French Warmblood) within 1 month of age and then at approximately 2 month intervals until weaning at approximately 6 months of age. The prevalence of limb deviations decreased from birth to weaning...
Watson ED.The mechanisms that permit maternal tolerance of the conceptus allograft during early pregnancy in the mare have not been investigated. Embryos and endometria were collected from mares 14 days after ovulation and cultured for 20.5 h. The effect of addition of culture supernatant on incorporation of [3H]thymidine by equine peripheral blood lymphocytes was studied. Culture supernatant from endometrium of nonpregnant mares did not affect lymphocyte blastogenesis, but supernatant from both embryos and endometrium of pregnant mares reduced concanavalin A (Con A)- and phytohemagglutinin-induced blas...
Kudrimoti S, Machin J, Arojojoye AS, Awuah SG, Eisenberg R, Fenger C, Maylin G, Lehner AF, Tobin T.Based on structural similarities and equine administration experiments, Barbarin, 5-phenyl-2-oxazolidinethione from Brassicaceae plants, is a possible source of equine urinary identifications of aminorex, (R,S)-5-phenyl-4,5-dihydro-1,3-oxazol-2-amine, an amphetamine-related US Drug Enforcement Administration (DEA) controlled substance considered illegal in sport horses. We now report the synthesis and certification of d -barbarin to facilitate research on the relationship between plant barbarin and such aminorex identifications. D -barbarin synthesis commenced with production of d -2-oxo-2-phe...
Bishop J, Heffron B, Taddei L, Benoit M, Hurt L, Costello S, Gross M, Negrusz A.Clenbuterol (CLE) is used in horses as a bronchodilator and for its anabolic steroid-like effects. CLE is a Class 3 drug according to current Association of Racing Commissioners International (ARCI) Uniform Classification Guidelines. The Racing Medication and Testing Consortium recommended a urine CLE threshold of 140 pg/mL after careful scientific review of the results of studies describing the disposition of CLE in the horse and this threshold was adopted by the ARCI. Enzyme-linked immunosorbent assay was previously used to screen samples for CLE in Illinois, but could not detect such low co...
Nankervis KJ, Tranquille CA, Chojnacka K, Tacey JB, Deckers I, Newton JR, Murray RC.Water treadmill (WT) exercise may induce limb and back kinematics that meet specific training and rehabilitation goals. The study aimed to investigate the effects of walk speed, at different water depths (WDs), on limb and back kinematics of six Thoroughbreds exercising on a WT. Horses walked at 2.8/4.3/5.5/6.0 km/h (i.e. 0.8/1.2/1.5/1.7 m/s) at dry, metacarpophalangeal and carpal WD. Videography captured limb movement in the sagittal plane. Motion-capture measured thoracolumbosacral flexion-extension (FE), and lateral bend (LB) ranges of movement (ROM) using skin surface markers on the sixt...
Tozaki T, Ohnuma A, Kikuchi M, Ishige T, Kakoi H, Hirota KI, Nagata SI.Individual identification and paternity testing are important for avoiding inbreeding in the management of small populations of wild and domestic animals. In horse racing industries, they are extremely important for identifying and registering individuals and doping control to ensure fair competition. In this study, we constructed an individual identification panel for horses by using insertion and deletion (INDEL) markers. The panel included 39 INDEL markers selected from a whole-genome INDEL database. Genotyping of 89 Thoroughbreds showed polymorphisms with minor allele frequencies (MAFs) of...
Massie SL, Bezugley RJ, McDonald KJ, Léguillette R.Arrhythmias are commonly reported in exercising horses, however due to regulatory constraints electrocardiograms (ECGs) are acquired during training but not competition, raising questions about the repeatability of findings. The aims were (1) compare training and competition arrhythmias and (2) describe the repeatability of arrhythmias during maximal-intensity exercise. A convenience sample of 52 healthy Thoroughbreds (aged 8.7 ± 2.5 years) competing in the World Professional Chuckwagon Association were obtained, totaling 152 training or competition ECGs (2-7 ECGs/horse). Speed, heart rate ...
Kerbert MP, Freeland RB, Verhaar N, Baker WT. The lateral trochlear ridge (LTR) of the femur is the most common predilection site for osteochondritis dissecans (OCD) in the equine stifle. The objective was to investigate the relationship between lesion size, racing performance, and sale result of Thoroughbreds with LTR OCD following arthroscopic removal as a yearling. Methods: In this retrospective study, medical records of 145 Thoroughbreds from one equine hospital that underwent surgery for LTR OCD were reviewed; the length and depth of the lesions were measured on preoperative radiographs. Horses were allocated to group S if they...
Katz LM, Gough K, McGivney CL, McGivney B, Sides RH, Hill EW, Bayly WM.Sex effects on ventilatory and oxygen consumption (V̇O) measurements during exercise have been identified in humans. This study's aim was to evaluate the hypothesis that there are sex effects on ventilatory and V̇O measurements in exercising, untrained yearling Thoroughbreds (Tb). Forty-one Tbs (16 colts, 25 fillies; 19.8 ± 1.4 months old) were recruited. Physiological, ventilatory and exercise data were gathered from horses exercising unridden at high intensity on an all-weather track from a global positioning-heart rate unit and a portable ergospirometry system. Data were analysed with an...
Zimmermann E, Ros KB, Pfarrer C, Distl O.Malformations of the equine cervicothoracic junction affect the C6 and C7 cervical vertebrae, the T1 thoracic vertebra and in variable extent the first and second sternal ribs. To date, the clinical impact of this malformation, its prevalence and mode of inheritance in equine populations are not yet determined. We examined five skeletons for signs of malformation of the cervicothoracic junction, including three skeletons from widely used Thoroughbred stallions affected with the malformation and two skeletons serving as a comparison. The three affected historical horses were the Thoroughbred st...
Ishimaru M, Okano A, Matsui A, Murase H, Korosue K, Akiyama K, Taya K.The effects of an extended photoperiod (EP) on body composition of Thoroughbreds colts and fillies from December at one year old to April at two years old were investigated. Seventy-three Thoroughbreds reared and trained in Hidaka Training and Research Center, Japan Racing Association, Hokkaido were used. Forty-one horses were under the EP conditions from December 20 to April 15, and the 32 horses were under natural light alone as the control group. Body weight (BW), rump fat thickness (RFT), fat free mass (FFM) and percentage of fat (%F) were used as parameters of body composition. The presen...
Sobotková E, Kopec T, Mikule V, Kuřitková D.The aim of the research was to assess how age, sex, sire, country of foaling, country of training and race distance influenced the international racing and performance of Thoroughbreds. The research was based on performance ratings of 6216 horses assigned by the International Federation of Racing Authorities between 2004 and 2022. The most common sex was stallion (58.54 %) and more than half of the population consisted of 3- and 4-year-old horses (54.68 %). The majority of the horses had the USA as their country of foaling (25.92 %) and also as their country of training (24.87 %). The ...
Martineau M, Kokabi E, Taiebi A, Lefebvre S, Pradier S, Jaÿ M, Tardy F, Leon A.Mycoplasmas are pathogens involved in respiratory disorders of various animal hosts. In horses, Mycoplasma (M.) equirhinis is the species most frequently detected in clinical respiratory specimens, with a prevalence of 12-16%, but its clinical implication in equine respiratory disorders remains unclear. Here we screened 1948 clinical specimens for the presence of M. equirhinis. The samples were both tracheal washes (TW) and bronchoalveolar lavages (BAL) collected by veterinarians in France in day-to-day work between 2020 and 2022. The samples were associated with a standardized form that serve...
Ryu SH, Sohn Y, Forbes E, Jeon HS, An SJ, Kim BS, Kyung SG, Lee I.The incidence of colic and the outcomes of colic surgery have not been surveyed in racetracks in Korea. Objective: This study examined the incidence, mortality, and case fatality of colic and investigated the effects of age and sex after an exploratory celiotomy on the long-term survival rate (return to racing), subsequent racing performance, and career longevity. Methods: The incidence, mortality, and case fatalities of colic were examined over an 11-year period. The records of 40 horses that had undergone a celiotomy, after participating in at least one race and 75 race-matched control horse...
