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.
Bowman DD, Cummings JF, Davis SW, deLahunta A, Dubey JP, Suter MM, Rowland PH, Conner DL.Morphological information is presented for syntype material of the etiologic agent of equine protozoal myeloencephalitis, Sarcocystis neurona. A clinical description of the horse from which the organism was isolated and the methodology used to immunosuppress the horse in an attempt to increase parasite numbers are also given. The description includes microscopic details observed both with light and transmission electron microscopy. Mainly stages from tissue are illustrated, but information is also presented on the development of the organism after inoculation onto monolayers of bovine monocyte...
Foster CV, Harris RC.There was no detectable loss of total carnitine associated with intense exercise from the middle gluteal muscle of Thoroughbred horses. Measurements made on a single biopsy obtained during the course of a normal training and exercise programme may, therefore, be considered representative of the normal content at rest. The variability in total carnitine content within the normal muscle biopsy area amounted to 13.2 per cent of the normal mean content. Approximately 50 per cent of this variability could be attributed to covariation with citrate synthase, to which it was highly significantly corre...
Johnson AT, Soma LR, Ferouz C.Exercise-induced pulmonary hemorrhage (EIPH) affects a large portion of racing thoroughbred horses. Sites of hemorrhage and causal mechanisms remain unestablished. Our mathematical model was constructed to test the hypothesis that EIPH could be caused by a combination of respiratory and circulatory mechanical factors occurring during exercise. Various physiological data for respiration, blood circulation and exercise were incorporated into the model. Results show that inhalation pressure drops across airway resistances become great enough during exercise to cause rupture of capillaries for bot...
Sewell DA, Harris RC.Adenine nucleotide (AN) degradation has been shown to occur during intense exercise in the horse and in man, at or close to the point of fatigue. The aim of the study was to compare the concentrations of muscle inosine 5'-monophosphate (IMP) and plasma ammonia (NH3) during intense exercise with the concentrations of muscle and blood lactate. Seven trained thoroughbred horses were used in the study. Each exercised on a treadmill for periods of between 30 s and 150 s, at 11 and/or 12 m.s-1. Blood and muscle samples were taken and analysed for lactate and NH3 and adenosine 5'-triphosphate (ATP), ...
Ellegren H, Andersson L, Johansson M, Sandberg K.A synthetic polynucleotide (TG)n was hybridized to equine DNA digested with HinfI and hypervariable hybridization patterns were obtained. Mendelian inheritance of these DNA fingerprinting patterns was confirmed by pedigree analysis. Estimates of the probabilities of identical band patterns in unrelated individuals of different breeds (Swedish Trotters, North Swedish Trotters, Thoroughbreds and Arabians) were in the range 1 x 10(-4) - 7 x 10(-6). The variability derived with the (TG)n probe in horses was higher than what we obtained with several other commonly used probes for DNA fingerprinting...
Lindner A, Offeney F.A review of the operational life, attrition and lethality rates, major causes of attrition and death for thoroughbred and standardbred race horses and competition horses is given. Because of the lack of data, it was not possible to supply answers for all the sport disciplines. The operational life in sports for thoroughbred race horses was 3.3 years, for standardbred horses 4.1 and for competition horses 5.5 years. Attrition and lethality rates could be determined only for the thoroughbred race horses. The yearly rates of attrition and lethality were 30% and 2% respectively. The major causes o...
Pick M.Intensive strain of racing-horses during training and race is not an end in itself but should be understood from the social task to create exceptionally efficient horses. This roughness in sports obliges the responsible associations to issue rigorous regulations for the protection of horses. In this paper, some physical and psychical disorders of racing-horses are described. Improved keeping conditions as well as performance-adapted training methods will help to avoid defects. The aids being used during training and races are critically investigated on their effects according to the regulation...
Harris P, Marlin D, Gray J.A similar and significant (P less than 0.001) increase in plasma thyroxine (T4) concentration was seen in seven clinically normal thoroughbred horses 2 h after the intravenous administration of either 2.5 iu or 5 iu of thyroid stimulating hormone (TSH) with a peak response around 4 h after administration. The intravenous administration of 0.2, 0.5 or 1 mg thyrotrophin releasing hormone (TRH) resulted in a significant (P less than 0.01) increase in T4 concentration in three groups of animals; six thoroughbreds in full work, five thoroughbreds at rest and four ponies at rest. The peak response w...
Yamamoto K, Yasuda J, Too K.In 101 newborn Thoroughbred foals and foaling mares, 45 fetal (FECGs) and 101 neonatal electrocardiograms (NECGs) were obtained to investigate neonatal arrhythmias and other parameters including changes in fetal (FHR) and neonatal heart rate (NHR). Moreover, umbilical arterial, venous and jugular venous blood gas tensions and pH immediately after birth were analyzed to compare with the type and the degree of neonatal arrhythmias. Before delivery, in 37 fetuses FHR gradually decreased while in 8 cases it increased after rupture of the chorio-allantois. Abnormal deliveries were related in 5 of t...
Mohammed HO, Hill T, Lowe J.A case-control study was conducted on Thoroughbred horses to identify factors associated with the risk of breakdown on racetracks. A total of 310 cases (breakdowns) were identified from the Horse Identification Department records kept by the chief examining veterinarian of New York Racing Association. For each case, two control horses were selected randomly from the Daily Racing Form Inc. records. Multiple logistic regression analysis was used to identify and quantify the risk of factors associated with breakdown, while simultaneously controlling for the effect of other putative factors. Facto...
Jaeschke G, Rudolph R.In a review supplementary to prior evaluations further hematological or cytodiagnostic aspects respectively of equine leucosis are discussed. Leukemic nature of the disease is characterized by increased count of normal blood cells or by the presence of morphologically non-differentiated cells in circulating blood or by disorder or loss of function of blood cells respectively. Thrombocytopenia in the most cases is accompanied by anemia, leukemia and tumor cell infiltration in bone marrow. Tumor cells in circulating blood indicate their presence in bone marrow too. In cases of equine leucosis wi...
Voros K, Holmes JR, Gibbs C.Two-dimensional echocardiography (2DE) was performed on 22 unsedated Thoroughbred and part Thoroughbred horses weighing between 411 and 650 kg to establish normal reference values for 2DE measurements. Animals stood during examinations performed with a 3.5 MHz mechanical sector transducer using various transducer positions and tomographic planes. Right ventricular diameter (RVD), ventricular septal thickness (VSTh), aortic diameter (AoD), area of the chordal lumen of the left ventricle (CTA), left ventricular diameter (LVD) and left atrial diameter (LAD) were determined at ventricular end-dias...
Humber KA, Beech J, Cudd TA, Palmer JE, Gardner SY, Sommer MM.Azathioprine, a thiopurine antimetabolite used in the treatment of immune-mediated thrombocytopenia in human beings and dogs, was used in 2 cases of immune-mediated thrombocytopenia in horses that failed to respond to corticosteroid therapy alone. Platelet counts were increased to acceptable values in both horses. One horse returned to a successful racing career, and the other was euthanatized after developing renal disease and mild laminitis.
Haven ML, Rottman JB, Bowman KF.A leiomyoma of the small colon was discovered incidentally in a 4-year-old Thoroughbred gelding during colic surgery to correct large colon displacement. The mass and 20 cm of small colon were resected, and an end-to-end anastomosis was performed. A postoperative fecal impaction proximal to the anastomosis responded after 5 days to administration of intravenous fluids, analgesics, and stool softeners.
Henninger RW, Bramlage LR, Schneider RK, Gabel AA.Case records of 25 horses with transverse fractures of the proximal sesamoid bone were reviewed to evaluate the success of treatment. All fractures were repaired by use of lag screw fixation and an autogenous cancellous bone graft because the fracture fragments were considered too large for surgical removal and reconstruction of the suspensory apparatus was necessary. Radiography was performed in all cases, and the fractures were classified into 3 types: (1) proximal midbody fractures, which included all fractures in the proximal aspect of the sesamoid bone that resulted in fragments involving...
Lowis TC, Hyland JH.This project surveys the reproductive performance of 154 foaling Thoroughbred mares on a commercial stud in southern Victoria. Of these, 96 were served on foal heat (FHS) and 58 were served at a subsequent prostaglandin-induced oestrus (PGS). The PGS group of mares performed more favourably in all aspects except the foaling-to-conception interval where there was a 9.4 day advantage to the FHS group. The first service conception rate in the FHS group was 47.9% compared with 55.2% in PGS mares. Second heat period conception rates were 46% vs 57.7% for FHS and PGS mares, respectively. Overall con...
Watson TD, Burns L, Love S, Packard CJ, Shepherd J.Plasma lipoproteins were isolated from eight Thoroughbred horses and eight Shetland ponies on the basis of particle size by gel filtration chromatography and according to density using rate-zonal ultracentrifugation. Three major classes corresponding to very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL) were identified and characterised by their lipid and apolipoprotein compositions. The particle size distributions of each class were determined by electron microscopy and non-denaturing polyacrylamide gradient gel electrophoresis. HDL was fo...
Clabough DL, Roberts MC, Robertson I.Esophageal stenosis was diagnosed in a 7-day-old Thoroughbred foal referred for evaluation of bilateral milky nasal discharge. Double-contrast radiography revealed concentric narrowing of the esophagus at the level of the fifth rib, overlying the base of the heart. Lateral displacement of the esophagus was not apparent. X-ray computed tomography of the cranial portion of the thorax confirmed normal cardiac and great vessel anatomy, ruling out vascular ring anomaly. A nasogastric tube was placed, extending past the stenosis and into the stomach, and the foal was fed mares' milk via this tube. O...
Röcken H, Wenz C.A unilateral malformation of the eye of a thoroughbred foal is described. The specific form of the tiny lens we named, "lenticulus". It is correlated with a maximal unchangeable mydriasis. The bulb shows physiological size. A brown-black pigmented mass inhibited (internal) inspection and examination of the middle and rear part of the eye. Special emphasis is laid on the insecure behaviour of the foal. A connection with an iridocyclochoroiditis, which was treated in the mare about a year ago, and the pathological changes in the eye of the foal is not evident.
Matsuda H, Koyama H, Oikawa M, Yoshihara T, Kaneko M.Addition of sera, collected from Thoroughbred horses after sprint exercise, induced significant neurite outgrowth from chick embryo dorsal root ganglia after a 24-hour culture. The nerve growth factor (NGF)-like activity was detected in sera collected immediately, or 1 hour or more, after the exercise. These findings suggest a possible role of serum NGF-like activity under stress conditions (running exercise) of horses.
Kannegieter NJ, Ryan N.The case record, and subsequent racing performance, of 110 horses that had undergone arthroscopic surgery of the carpus, were reviewed. Of these, 87% resumed racing, with 43% able to win at least one race, after surgery. Horses with chip fractures from the distal radius had the best prognosis, while horses with sagittal fractures of the third carpal bone had the poorest. The performance of horses with bilateral lesions was similar to those with unilateral lesions. It was concluded that arthroscopic surgery was a suitable technique for the diagnosis and treatment of carpal lesions in the horse....
Young DR, Nunamaker DM, Markel MD.Eight untrained 2-year-old Thoroughbred horses were used in a study of the remodeling response of the proximal sesamoid bone (PSB) to training-related stimuli. Two horses each were assigned to 1 of 4 groups: group 1, untrained, pasture turnout (control); group 2, modified-classically trained, dirt track; group 3, classically trained, dirt track; and group 4, classically trained, wood chip track. Horses were given fluorochromic bone labels every 28 days during training. All horses were euthanatized after 5 months of training, and the proximal sesamoid bones (PSB) were removed. A midsagittal sec...
Watson TD, Sullivan M.The effects of sedation with detomidine on oesophageal function were assessed by contrast radiography in 10 healthy adult thoroughbred horses. Barium swallows were monitored by means of image intensification, first without sedation and then after the intravenous administration of detomidine at doses of 10 and 20 micrograms/kg bodyweight. The transit time of contrast agent to the oesophageal hiatus was recorded and each swallow was scored for markers of oesophageal dysfunction. Analysis of the data indicated that there were highly significant dose dependent increases in the transit time, the re...
Hoskinson JJ, Wooten P, Evans R.Nonsurgical, percutaneous, transvenous removal of a catheter fragment embolus was performed in a 14-day-old Thoroughbred foal. A basket retrieval catheter was introduced into the jugular vein and manipulated under fluoroscopic guidance to remove the fragment from the right side of the heart. Percutaneous retrieval should be considered as an alternative to thoracotomy for retrieval of intracardiac or intravascular foreign bodies.
Charlton C, Tulleners E.Two male racehorses (1 Standardbred, 1 Thoroughbred) were examined because of intraluminal cervical tracheal lesions, located 60 to 70 cm from the nares. A contact neodymium:yttrium aluminum garnet laser with a chisel probe attached to the fiber end was used to transendoscopically debride a nonhealing tracheal ulcer and to excise a pyogranulomatous mass. In both horses, the surgical sites healed quickly and the lesions did not redevelop.
McKellar QA, Bogan JA, von Fellenberg RL, Ludwig B, Cawley GD.Carprofen, a non-steroidal anti-inflammatory drug (NSAID) was administered to three Thoroughbred geldings and three Shetland ponies to determine its plasma disposition and tolerance. The main pharmacokinetic characteristics of carprofen in horses and ponies were a volume of distribution of 0.08 to 0.32 litres/kg (mean +/- se = 0.23 +/- 0.04) a systemic clearance of 26.4 to 78.5 ml/min (mean +/- se = 44.9 +/- 8.0) and a plasma elimination half-life of 14.5 to 31.4 h (mean +/- se = 21.9 +/- 2.3). There was no evidence of any accumulation of carprofen in plasma when the drug was given orally at a...
Dow SM, Leendertz JA, Silver IA, Goodship AE.In this study a method of analysing ground reaction forces was developed to help in the diagnosis of subclinical flexor tendon injury. A Kistler force plate was used to obtain records from a population of Thoroughbreds in National Hunt training over a period of two years. Characteristic features of the force patterns generated were measured and shown to have low variance, both between horses and over a period of two racing seasons in animals that were sound throughout the trial. Specific changes in the loading pattern of the limb, which correlated with injury of the superficial digital flexor ...
Rose PL, Schumacher J, Taylor TS.An extensive stricture of the left dorsal colon in a Thoroughbred colt was resected and the colon was anastomosed. In two horses, circumferential strictures at the pelvic flexure 2.5 to 3 cm long were corrected with a modified Heineke-Mikulicz pyloroplasty technique. The horses were reported to be doing well at 6, 8, and 45 months, respectively.
Axling JM, Castle K, Velie BD, Tammen I, Thomson PC, Hamilton NA, Raadsma HW, Lindgren G, Jeffcott LB, Nicholas FW.Diagnostic reports written to assist stud managers in the sale of young Thoroughbreds have not previously been used as a data source for the study of skeletal lesions. However, analyses of these reports may provide efficient and cost-effective insights into the prevalence and distribution of skeletal lesions within a population. Diagnostic reports written by veterinarians were acquired from Thoroughbred stud managers in Australia and New Zealand. The reports were based on approximately 1300 sets of weanling and yearling radiographs taken between 2002 and 2007. The prevalence and anatomical dis...
Munday JS, Grant K, Orbell G, Vaatstra BL.A 6-year-old Thoroughbred mare developed multiple flat plaques, < 1 cm in diameter, on the left front fetlock. These were treated topically using 5-fluorouracil and resolved after 4 weeks. However, additional similar plaques developed on the left front pastern 5 months later. These lesions resolved within 3 months without treatment. Unassigned: One plaque that developed initially and one plaque that developed later were examined histologically. Both consisted of well-demarcated foci of moderate epidermal hyperplasia. Scattered throughout both plaques were cells showing evidence of papillo...
Brown VA, Wilkins PA.Techniques for novel approaches to the diagnosis and management of equine pulmonary disease continue to be developed and used in clinical practice. Diagnostic techniques involving immunoassays and nucleic acid-based tests not only decrease the time in which results become available but increase the sensitivity and specificity of test results. These assays do not substitute for careful clinical evaluation but can shorten the time to a confirmed accurate diagnosis, and thus allow for early initiation of therapeutic strategies and prevention protocols. With further understanding of the molecular ...
Chan CW, Collins EA.An angiosarcoma involving the right frontal and maxillary sinuses in a nine-year-old Thoroughbred mare was studied post mortem by light and electron microscopy. Important diagnostic features included malignant endothelial cells lining ill-defined vascular spaces, supported by other vasoformative elements. Rhabdomyoblasts were also found. The tumour is apparently rarely seen in the nasal passages of the horse.
Meredith TB, Dobrinski I.To determine whether thyroid function was associated with pregnancy status in broodmares. Methods: Prospective study. Methods: 79 Thoroughbred and Standardbred broodmares between 2 and 22 years old. Methods: Serum triiodothyronine (T3) concentration was measured before and 2 hours after i.v. administration of thyrotropin releasing hormone (TRH), and serum thyroxine (T4) concentration was measured before and 4 hours after TRH administration. Pregnancy status was monitored by means of transrectal ultrasonography beginning 16 days after ovulation. Results: Baseline T3 and T4 concentrations varied...
Sasaki N, Hobo S, Yoshihara T.This study concerns the establishment of a simple testing method for breath concentration of hydrogen and methane in horses. Twenty-eight healthy thoroughbreds and 24 Arabians were used. Breath samples were collected using one-minute closed circulatory respiration through an aluminum bag filled with 10 liters of pure oxygen, which was mounted on the subjects by means of a face mask. Breath samples obtained, were analyzed by gas chromatography. A significant correlation in both hydrogen and methane levels was observed for samples collected at separate times. These findings confirmed the usefuln...