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.
Gu J, Li S, Zhu B, Liang Q, Chen B, Tang X, Chen C, Wu DD, Li Y.Understanding the genetic variations of the horse (Equus caballus) genome will improve breeding conservation and welfare. However, genetic variations in long segments, such as structural variants (SVs), remain understudied. We de novo assembled 10 chromosome-level three-dimensional horse genomes, each representing a distinct breed, and analysed horse SVs using a multi-assembly approach. Our findings suggest that SVs with the accumulation of mammalian-wide interspersed repeats related to long interspersed nuclear elements might be a horse-specific mechanism to modulate genome-wide gene regulato...
Hayes AM, Kastl B, Perry E, Moore AR, Springer NL.Myeloma-related disorders, including multiple myeloma, extramedullary plasmacytoma, and solid osseous plasmacytoma, are rare in horses. Clinical complaints for myeloma-related disorders are nonspecific, and when present, M-protein location is more variable on protein electrophoresis in horses relative to dogs and cats. Here, we describe a case of a 15-year-old Thoroughbred mare who presented with recurrent blepharitis. Marked hyperglobulinemia was an incidental finding on routine hematologic and biochemical testing. Bone marrow aspiration consisted of >30% plasma cells, and serum protein el...
Sharman P, Wilson AJ.Several studies over recent decades have reported a lack of contemporary improvement in thoroughbred racehorse speed, despite apparent additive genetic variance and putatively strong selection. More recently, it has been shown that some phenotypic improvement is ongoing, but rates are low in general and particularly so over longer distances. Here we used pedigree-based analysis of 692,534 records from 76,960 animals to determine whether these phenotypic trends are underpinned by genetic selection responses, and to evaluate the potential for more rapid improvement. We show that thoroughbred spe...
Takahashi Y, Takahashi T, Mukai K, Ebisuda Y, Ohmura H.Given that Thoroughbred horses' canter is an asymmetric gait, not only speed but also leading or trailing limbs could affect muscle activities. However, the muscle activity during a canter remains poorly understood. Hence, we aimed to investigate speed and lead-side (leading or trailing) effects on surface electromyography (sEMG) during a canter. The sEMG data were recorded from left Musculus brachiocephalicus (Br), M. infraspinatus (Inf), long head of M. triceps brachii (TB), M. gluteus medius (GM), M. semitendinosus (ST), and M. flexor digitorum longus of seven Thoroughbreds with hoof-strain...
Kis J, Rózsa L, Husvéth F, Mezőszentgyörgyi D, Kovács S, Bakos Z, Zsolnai A, Anton I.The g.66493737C/T polymorphism of the myostatin gene (MSTN) majorly influences muscle fiber composition and best race distance of Thoroughbreds. Thus, a better understanding of this process may lead to superior genetic exploitation for maximizing Thoroughbred athletic potential. Our objective is to investigate whether myostatin genotypes are associated with muscular development and cardiac variables of Thoroughbreds. Echocardiography and muscular ultrasonography were performed on three groups having C/C, C/T, and T/T genotypes, respectively. Each group consisted of 22 animals. Homogeneity of v...
Bamford NJ, Stewart AJ, El-Hage CM, Bertin FR, Bailey SR.Plasma adrenocorticotropic hormone (ACTH) concentration is commonly measured to diagnose pituitary pars intermedia dysfunction (PPID). Several intrinsic and extrinsic factors affect ACTH concentrations, including breed. The objective of this study was to prospectively compare plasma ACTH concentrations among different breeds of mature horses and ponies. Three breed groups comprised Thoroughbred horses (n = 127), Shetland ponies (n = 131) and ponies of non-Shetland breeds (n = 141). Enrolled animals did not show any signs of illness, lameness or clinical signs consistent with PPID. Blood ...
Sloan PB, White B, Santschi EM.Osteochondrosis dissecans (OCD) is common in the femoropatellar joint in Thoroughbred yearlings for sale at auction and there is no consensus on the effect on racing outcomes. Objective: Describe femoropatellar OCD in juvenile Thoroughbreds and compare the racing performance of affected Thoroughbred horses to siblings and unaffected horses from the same sale. Methods: Retrospective case-control study of juvenile horses born 2010-2016. Methods: Radiographic reports from 27 Thoroughbred auctions of weanling (5-11 months of age) and yearling (12-22 months of age) horses were reviewed to ident...
Mouncey R, Arango-Sabogal JC, de Mestre AM, Verheyen KL.Up-to-date estimates of early-life morbidity and mortality in Thoroughbreds are lacking. Methods: A birth cohort was established on Thoroughbred stud farms across the UK and Ireland. All veterinary interventions for disease or injury between birth and 18 months of age or leaving the study were recorded. Multilevel Poisson regression models with farm and foal as random effects were fitted to estimate incidence rates. Results: Data were available for 3328 foal-months at risk for 275 foals on seven farms. The overall rates of disease and injury requiring veterinary intervention and mortality were...
Oheida AH, Shalgum AA, Alrtib AM, Booker AO, Ben-Naser KM, Davies HMS.Carpal conformation is an important factor in relation to joint soundness. The equine carpometacarpal joint (CMCJ) was reported to have variations in its three palmaromedial articulations. Lacking one or more of these articulations has not been radiographically evaluated in Thoroughbred (TB) and Standardbred (SB) racehorses. The study aimed to identify the prevalence of the variation in the palmaromedial articulation of the carpometacarpal joint (PM-CMCJ) in TB and SB horses. Additionally, to detect the probability of having each of the three articulations within and between the breeds. Finall...
Flash ML, Shrestha K, Stevenson MA, Gilkerson JR.The social licence of the Australian thoroughbred (TB) industry relies on the general public's perception of how they manage the animal in their care. Methods: This study examines the horse, race and activity records for the 37,704 horses racing and training in Australia from 1 August 2017 to 31 July 2018. Three-quarters (75%, n = 28,184) of TBs started in one of the 180, 933 race starts that occurred during the 2017-2018 Australian racing season. Results: Horses participating in the 2017-2018 Australian racing season had a median age of 4 years, with geldings more likely to be aged 5 ye...
Martins AV, Corrêa LL, Ribeiro MS, Lobão LF, Dib LV, Palmer JPS, de Moura LC, Knackfuss FB, Uchôa CMA, Molento MB, Barbosa ADS.The aims of this study were to determine the prevalence of helminths in Thoroughbred horses in Rio de Janeiro; make correlations with risk factors for these infections; and compare the efficiency of three floatation solutions applied in the quantitative Mini-FLOTAC technique. Fecal samples from 520 horses were collected from six training centers between 2019 and 2021. These were subjected to the Mini-FLOTAC technique using three solutions: NaCl (density = 1.200 g/mL), ZnSO4 (1.350 g/mL) and ZnSO4 (1.200 g/mL); and also to qualitative techniques. Information on the horses' sex and age of hors...
Breen LJ, Coleridge MOD, O'Brien T.A 6-month-old thoroughbred colt foal was referred to a private equine referral hospital for evaluation of an acute onset, left hind limb lameness. On arrival the foal was 4/5 lame on the left hind at walk and there was diffuse swelling of the left hind pastern and fetlock region. The physical exam was otherwise unremarkable. Digital radiographs of the left hind pastern identified a Salter-Harris type-2 physeal fracture of the proximal phalanx. The fracture was initially treated conservatively using a cast, but the immobilization was not sufficient at achieving adequate reduction. As a result, ...
Steel C, Ahern B, Zedler S, Vallance S, Galuppo L, Richardson J, Whitton C, Young A.Radiographs underestimate the extent of bone injury in horses with third carpal bone (C3) fractures (Fx). We aimed to describe bone pathologies identified using computed tomography (CT) and compare the diagnostic value of digital radiography (DR) and CT in horses with C3 Fx. CT images of 15 racehorses with C3 Fx and 10 controls were reviewed (Part 1) then DR and CT images of 26 racehorses (24 Thoroughbred, 2 Standardbred) with C3 Fx (Part 2) were evaluated. Agreement on fracture geometry and concomitant bone lesions was tested between DR and CT using the kappa statistic (Part 2). For agreement...
Sugiyama F, Takahashi Y, Nomura M, Ebisuda Y, Mukai K, Yoshida T.We investigated the risk factors for epistaxis in Japanese flat races over a 20-year period. The veterinary records of horses identified as having epistaxis by endoscopy on the race day, and the official racing records of all flat races from April to September between 2001 and 2020, were reviewed. The racecourses (n = 10), surface type, surface condition, race class, race distance, race year, sex, age, two training centers, ambient temperature, and body weight on race days were assessed using multivariable logistic regression (p < 0.05). Of 475,709 race starts, 616 (1.30 cases per 1000 starts;...
Camp M, Kibler ML, Ivey JLZ, Thompson JM.Racehorse welfare is a prominent, public issue which affects nearly every aspect of the racing industry. Thoroughbred care after race career completion has garnered increasing attention from the equine industry, general public, and animal welfare groups alike. As the average racehorse's career lasts just 4.5 years, owner demand for thoroughbreds is essential for post-race careers and acceptable welfare standards. This study utilized data from and hedonic pricing models to analyze buyer demand for thoroughbreds sold in online auctions held from 2012 to 2020. The results indicate buyer preferenc...
Maxwell L, McCarrel TM, Hay S, Cole C.The antifibrinolytic agent aminocaproic acid (ACA) is occasionally used prior to episodes of intense training in racehorses suffering from exercise-induced pulmonary hemorrhage. Although a previous study indicated that the drug is cleared rapidly in horses, some racetrack practitioners claim that recent adverse analytical findings for ACA in postrace samples were from ACA administrations 5-7 days before the race. The purpose of this study was to re-examine the pharmacokinetics of ACA in horses to address this apparent conundrum. Eight exercise-conditioned thoroughbred horses were administere...
Pompermayer E, Hoey S, Ryan J, David F, Johnson JP.The objective of this study was to compare the skull morphology of the Straight Egyptian Arabian (SEAR) to the Thoroughbred (TB), using computed tomography (CT) in the context of surgical procedures commonly performed on the equine head. Methods: Measurements relating to surgical considerations of the equine head were taken from 29 clinically normal adult horses (15 SEAR, 14 TB). Methods: A clinical prospective study. Standing skull CTs were performed. Fourteen gross and 10 CT measurements were taken. Results: Several variables showed a significant difference between groups, in all cases great...
Karatt TK, Sathiq MA, Laya S, Kal AKK, Subhahar MB, Muhammed Ajeebsanu MP, Philip M, Caveney MR, Graiban FM.Nonsteroidal selective androgen receptor modulators (SARMs) are a novel class of compounds that have not yet been clinically approved; however, they appear to have a better anabolic/androgenic ratio than steroids and cause slighter side effects. Sports drug testing laboratories are required to maintain continuously updated doping control analytical methods in light of the widespread misuse of SARMs in elite and amateur sports. This paper describes the metabolic conversion of SARM GSK2881078 in thoroughbred horses following oral administration and in vitro with equine liver microsomes. A liquid...
Holtby AR, Hall TJ, McGivney BA, Han H, Murphy KJ, MacHugh DE, Katz LM, Hill EW.Behavioural plasticity enables horses entering an exercise training programme to adapt with reduced stress. We characterised SNPs associated with behaviour in yearling Thoroughbred horses using genomics analyses for two phenotypes: (1) handler-assessed coping with early training events [coping] (n = 96); and (2) variation in salivary cortisol concentration at the first backing event [cortisol] (n = 34). Using RNA-seq derived gene expression data for amygdala and hippocampus tissues from n = 2 Thoroughbred stallions, we refined the SNPs to those with functional relevance to behaviour by c...
Pressanto MC, Pepe M, Coomer RPC, Pilati N, Beccati F.The purpose of this prospective study was to investigate the prevalence and severity of radiographic abnormalities of the interspinous spaces (ISSs) in the thoracolumbar vertebral column of unbroken yearlings and to compare these findings with a group of older trained Thoroughbred horses without perceived back pain. Yearlings (n = 47) and trained horses (55); 102 total. Each horse underwent a digital radiographic study of the thoracolumbar vertebral column (T7-L3) and each space graded for narrowing of the ISSs, increased opacity, radiolucency, and modeling of the cranial and caudal margins of...
Panizzi L, Dittmer KE, Vignes M, Doucet JS, Gedye K, Waterland MR, Rogers CW, Sano H, McIlwraith CW, Riley CB.Biomarkers for osteoarthritis (OA) in horses have been extensively investigated, but translation into clinical use has been limited due to cost, limited sensitivity, and practicality. Identifying novel biomarkers that overcome these limitations could facilitate early diagnosis and therapy. This study aimed to compare the concentrations of synovial fluid (SF) and plasma cell-free DNA (cfDNA) over time in control horses with those with induced carpal OA. Following an established model, unilateral carpal OA was induced in 9 of 17 healthy Thoroughbred fillies, while the remainder were sham-operate...
Trigg LE, Lyons S, Mullan S.The development of exertional heat illness (EHI) is a health, welfare and performance concern for racehorses. However, there has been limited multivariable assessment of the possible risk factors for EHI in racehorses, despite such information being vital for regulators to effectively manage the condition. Consequently, this study aimed to identify the risk factors associated with the occurrence of EHI in Thoroughbred racehorses and assess the ability of the risk factor model to predict the occurrence of EHI in racehorses to assist in early identification. Runners at British racecourses record...
Bull KE, Allen KJ, Hodgkinson JE, Peachey LE.In recent years, resistance to the benzimidazole (BZ) and tetrahydropyrimidine (PYR) anthelmintics in global cyathostomin populations, has led to reliance on the macrocyclic lactone drugs (ML-of which ivermectin and moxidectin are licensed in horses) to control these parasites. Recently, the first confirmed case of resistance to both ivermectin (IVM) and moxidectin (MOX) was reported in the USA in yearlings imported from Ireland. This suggests that ML resistance in cyathostomins has emerged, and raises the possibility that regular movement of horses may result in rapid spread of ML resistant c...
Walshe N, Burrell A, Kenny U, Mulcahy G, Duggan V, Regan A.In view of the rising threat of anthelmintic resistance in parasite populations and the planned change of classification of anthelmintics in Ireland for food animals to prescription-only medicines, there is a need for increased focus on parasite control strategies for horses. Effective parasite control programs (PCPs) are complex, necessitating the application of risk-assessment based on host immune status, infection pressure, type of parasite and seasonality to determine the requirement for anthelmintic administration and an understanding of parasite biology to employ effective, non- therapeu...
Tozaki T, Ohnuma A, Kikuchi M, Ishige T, Kakoi H, Hirota KI, Takahashi Y, Nagata SI.Thoroughbreds are some of the most famous racehorses worldwide and are currently animals of high economic value. To understand genomic variability in Thoroughbreds, we identified genome-wide insertions and deletions (INDELs) and obtained their allele frequencies in this study. INDELs were obtained from whole-genome sequencing data of 101 Thoroughbred racehorses by mapping sequence reads to the horse reference genome. By integrating individual data, 1,453,349 and 113,047 INDELs were identified in the autosomal (1-31) and X chromosomes, respectively, while 18 INDELs were identified on the mitoch...
Turco S, Gabbianelli F, Mavian CN, Pietrucci D, De Paolis L, Gialletti R, Mechelli L, De Ciucis CG, Cappelli K, Dell'Anno F, Mecocci S, Donato GG....Papillomaviruses (PVs) are small, non-enveloped viruses, ubiquitous across the animal kingdom. PVs induce diverse forms of infection, such as cutaneous papillomas, genital papillomatosis, and carcinomas. During a survey on the fertility status of a mare, a novel PV (EcPV) has been identified using Next Generation Sequencing, and it was further confirmed with genome-walking PCR and Sanger sequencing. The complete circular genome 7607 bp long shares 67% average percentage of identity with EcPV9, EcPV2, EcPV1, and EcPV6, justifying a new classification as PV 10 (EcPV10). All EcPV genes are cons...
Hill EW, McGivney BA, MacHugh DE.The proportion of the genome containing runs of homozygosity (ROH) affects production traits in livestock populations. In European and Australasian Thoroughbreds inbreeding, quantified using ROH (F ), is associated with the probability of ever racing. Here, we measured F using 333 K SNP genotypes from 768 Thoroughbred horses born in North America to evaluate the effect of inbreeding on racing traits in that region. Among North American horses, F was not associated (p = 0.518) with the probability of ever racing but was significantly associated with the number of race starts (p = 0.002). ...
Noordwijk KJ, Chen L, Ruspi BD, Schurer S, Papa B, Fasanello DC, McDonough SP, Palmer SE, Porter IR, Basran PS, Donnelly E, Reesink HL.Proximal sesamoid bone (PSB) fracture is the leading cause of fatal musculoskeletal injury in Thoroughbred racehorses in Hong Kong and the US. Efforts are underway to investigate diagnostic modalities that could help identify racehorses at increased risk of fracture; however, features associated with PSB fracture risk are still poorly understood. The objectives of this study were to (1) investigate third metacarpal (MC3) and PSB density and mineral content using dual-energy X-ray absorptiometry (DXA), computed tomography (CT), Raman spectroscopy, and ash fraction measurements, and (2) investig...
Marzok M, Kandeel M, Babiker H, Alkhodair KM, Farag A, Ibrahim H, El-Ashker M, Alghuwainem Y, El-Khodery S.The purpose of this study was to provide a systematic meta-analysis on echocardiographic measurements in normal Thoroughbred and Standardbred horses. The current systematic meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). All the available published papers on the reference values of echocardiographic assessment via M-mode echocardiography were searched, and fifteen studies were finally selected for analysis. In both fixed and random effect, the confidence interval (CI) for the interventricular septum (IVS) was 2.8-3.1 and 4.7-7.5; for the ...
Zielińska P, Soroko-Dubrovina M, Dudek K, Ruzhanova-Gospodinova IS.The reason for undertaking this study was to investigate soft tissue response to high-intensity laser therapy (HILT) by measuring changes in skin surface temperature and longissimus dorsi muscle tone in the thoracolumbar back area in Thoroughbreds with back pain and diagnosed with and without Kissing Spines Syndrome (KSS). Thoroughbreds aged 3-4 years with clinically presented back pain underwent a radiological examination (to assess a lack or presence of KSS) and longissimus dorsi muscle palpation (to assess muscle tone and pain degree). The subjects were divided into two groups, those with K...
Wada S, Hobo S, Niwa H.To describe the number of cases, etiologies, healing times, and results of microbial culture and susceptibility testing of corneal ulcers in thoroughbred racehorses in Japan. Methods: Retrospective study of the medical records of racehorses belonging to the Japan Racing Association (JRA) from 1997 to 2008. Results: A total of 2846 horses suffered ulcerative keratitis. These horses accounted for 90.5% of all the corneal problems and 54.9% of the entire number of horses with ocular diseases. Running in races was the cause in 64.3% of the cases. The mean healing time of the ulcers developed in ra...
Hlastala MP, Bernard SL, Erickson HH, Fedde MR, Gaughan EM, McMurphy R, Emery MJ, Polissar N, Glenny RW.Recent studies using microspheres in dogs, pigs and goats have demonstrated considerable heterogeneity of pulmonary perfusion within isogravitational planes. These studies demonstrate a minimal role of gravity in determining pulmonary blood flow distribution. To test whether a gravitational gradient would be more apparent in an animal with large vertical lung height, we measured perfusion heterogeneity in horses (vertical lung height = approximately 55 cm). Four unanesthetized Thoroughbred geldings (422-500 kg) were studied awake in the standing position with fluorescent microspheres injected ...
Asgarali Z, Coombs DK, Mohammed F, Campbell MD, Caesar E.Ninety-three (93) horses were investigated for serum antibodies to Theileria equi (T. equi) and Babesia caballi (B. caballi) using the immunofluorescent antibody test (IFAT). Seventy-seven (82.8%) horses were seropositive; 31 (33.3%) were positive to T. equi compared to 64 (68.8%) to B. caballi while 18 (19.4%) horses were seropositive to both parasites. No significant differences in antibody frequencies among females and males for either T. equi or B. caballi were noted. Differences in seropositivity to B. caballi among age groups were not significant. Antibodies to T. equi were more frequent...
Patterson-Kane JC, Parry DA, Birch HL, Goodship AE, Firth EC.The superficial digital flexor tendon is the most commonly injured tendon in the racing Thoroughbred. Despite the clinical significance of this structure, only limited data exist regarding normal age-related morphology of the tensile units, the collagen fibrils. The age at which these collagen fibrils become mature in composition and structure may be of importance. Consequently, the association of age and collagen fibril crosslink composition, diameter distribution and crimp morphology in the superficial and deep digital flexor tendons of Thoroughbreds up to and including three years of age ha...
Mellor DJ, Burns M.This review outlines the processes followed by New Zealand Thoroughbred Racing (NZTR) when developing its Thoroughbred Welfare Assessment Guidelines. It accepted that guidance on welfare management must be based on up-to-date knowledge of how animal welfare is understood scientifically. NZTR established an expert panel to facilitate this process. First, major changes in animal welfare science thinking over the last 40 years were considered. For example, the separate biological function and affective state orientations were later accepted as dynamically interacting elements within the body oper...
Gildea S, Arkins S, Walsh C, Cullinane A.Many racing authorities, sales companies and equestrian bodies have mandatory vaccination policies for equine influenza (EI). The consequences of lack of vaccine efficacy include clinical disease, disruption to training programmes, the cancellation of equestrian events and the introduction of virus to susceptible populations. The correlation between antibody against the virus haemagglutinin and protection against influenza has been well established. The objective of this study was to compare the antibody responses of 66 unvaccinated Thoroughbred weanlings on four different stud farms, followin...
Morita H, Nakano A, Shimazu M, Toh H, Nakajima F, Nagayama M, Hisamatsu S, Kato Y, Takagi M, Takami H, Akita H, Matsumoto M, Masaoka T, Murakami M.To detect the predominant lactobacilli in the intestinal flora of healthy thoroughbreds, we isolated lactobacilli from the feces of nine thoroughbreds (five males and four females; 0-15-year-old). The isolated lactobacilli comprise 17 species (37 strains), and they were classified into five groups: Lactobacillus salivarius (6 species), L. reuteri (6 species), Lactobacillus delbrueckii (3 species), L. buchneri (1 species) and L. vitulinus (1 species). On the basis of 16S rRNA gene sequences, we identified 3 other phylogenetic relatives belonging to the genus Lactobacillus. These results suggest...
Cogger N, Perkins N, Hodgson DR, Reid SW, Evans DL.Musculoskeletal injuries (MSI) in racehorses have been identified as the most common cause of lost training days and weeks spent resting at pasture. Several training-, track- and horse-related risk factors have been identified. However, there is no clear understanding of the inter-relationship between these factors. The aim of this longitudinal cohort study was to investigate risk factors for MSI in 2-year-old Thoroughbred racehorses. Australian Thoroughbred trainers were convenience sampled and enrolled in a 27-month longitudinal cohort study. The study population consisted of all 2-year-old ...
Tanner JC, Rogers CW, Firth EC.There is increasing evidence that exercise early in life has a positive effect on musculoskeletal health. At present, there is little whole population research investigating the effect of racing as 2-year-olds on future racing career. Objective: To investigate the association between attaining training milestones as 2-year-olds with length of career and racing success in Thoroughbred horses in New Zealand. Methods: Retrospective data were obtained of the 2001/02-born Thoroughbred foal crop. The 3 training milestones were: registered with a trainer, trialled and raced. The association of the tr...
van de Goor LH, van Haeringen WA, Lenstra JA.As a consequence of the close integration of horses into human society, equine DNA analysis has become relevant for forensic purposes. However, the information content of the equine Short Tandem Repeat (STR) loci commonly used for the identification or paternity testing has so far not been fully characterized. Population studies were performed for 17 polymorphic STR loci (AHT4, AHT5, ASB2, ASB17, ASB23, CA425, HMS1, HMS2, HMS3, HMS6, HMS7, HTG4, HTG6, HTG7, HTG10, LEX3 and VHL20) including 8641 horses representing 35 populations. The power of parental exclusion, polymorphic information content...
Patterson-Kane JC, Firth EC.Despite the high incidence of superficial digital flexor tendon (SDFT) injury in racehorses, the pathobiology of the condition is not clearly defined. The SDFT improves locomotor efficiency by storing elastic energy, but as a result it has low mechanical safety margins. As with the Achilles tendon in humans, rupture during athletic activity often follows accumulation of exercise and age-induced degenerative change that is not repaired by tenocytes. There is limited understanding of tenocyte biology and pathology, including responses to high mechanical strains and core temperatures during exerc...
Ireland JL, Clegg PD, McGowan CM, Platt L, Pinchbeck GL.Geriatric horses (aged≥15 years) now represent a substantial proportion of the equine population, yet mortality rates for aged horses in the UK have not previously been described. Although post-mortem studies have provided some data regarding specific causes of death, "old age" is a common owner-reported reason for euthanasia of adult horses, indicating further elucidation of reasons for death or euthanasia is required for the geriatric equine population. The objective of this cohort study was to describe mortality rates, causes of death or euthanasia and factors associated with mortality in...
Morrice-West AV, Hitchens PL, Walmsley EA, Stevenson MA, Whitton RC.Musculoskeletal injuries (MSI) in racehorses are commonly due to bone fatigue, a function of the number of cycles (strides) and the magnitude of load applied to the limb. These parameters can be estimated using speed and distance, with greater than 6000 m/month at a gallop (>14 m/s), in combination with canter distances greater than 44,000 m/month, reported to increase fracture risk. Despite their importance, there are limited data on the distances and speeds horses are exposed to during training. Objective: Estimate training volume at different speeds undertaken by Australian Thoroughbr...
Hinchcliff KW, Jackson MA, Brown JA, Dredge AF, O'Callaghan PA, McCaffrey JP, Morley PS, Slocombe RE, Clarke AF.To determine the interobserver variability of assessment of exercise-induced pulmonary hemorrhage (EIPH) during tracheobronchoscopic examination in horses. Methods: 747 Thoroughbred racehorses. Procedures-850 tracheobronchoscopic examinations were performed within 2 hours of racing for the horses. Examinations were recorded on videotape, and EIPH and its severity were assessed independently by 3 veterinarians. Concordance was determined by calculation of the Cohen weighted kappa statistic and tabulation of scores assigned by each observer. Results: Weighted kappa statistics ranged from 0.75 to...
Nagahisa H, Mukai K, Ohmura H, Takahashi T, Miyata H.Hypoxic training is believed to increase endurance capacity in association with hypoxia inducible factor-1 (HIF-1), a modulator of vascular endothelial growth factor-A (VEGF-A), and to influence activation of satellite cells (SCs). However, the effect of hypoxic training on SC activation and its relation to angiogenesis has not been thoroughly investigated. Eight Thoroughbred horses were subjected to normoxic (F = 21%) or hypoxic (F = 15%) training for 3 days/week (100% [Formula: see text]) for 4 weeks. Incremental exercise tests (IET) were conducted on a treadmill under normoxia and the ...
Escalona EE, Leng J, Dona AC, Merrifield CA, Holmes E, Proudman CJ, Swann JR.Metabonomics is emerging as a powerful tool for disease screening and investigating mammalian metabolism. This study aims to create a metabolic framework by producing a preliminary reference guide for the normal equine metabolic milieu. Objective: To metabolically profile plasma, urine and faecal water from healthy racehorses using high resolution (1) H-nuclear magnetic resonance (NMR) spectroscopy and to provide a list of dominant metabolites present in each biofluid for the benefit of future research in this area. Methods: This study was performed using 7 Thoroughbreds in race training at a ...
Rivero JL, Talmadge RJ, Edgerton VR.The histochemical myofibrillar ATPase (mATPase) method is used routinely for identification of equine skeletal muscle fiber types, but important problems have been observed with the subdivision of fast fiber population when using this method. To verify the use of this qualitative method, a number of equine muscle biopsies were analyzed with a combination of histochemical, immunohistochemical, electrophoretic, and morphometric techniques. The influence of training on these interrelations was also evaluated. Methods: Five young (2-3 years old) thoroughbred horses were intensively trained for 8 m...
Bell RJ, Kingston JK, Mogg TD, Perkins NR.To establish the prevalence and factors influencing the prevalence and severity of gastric ulceration in racehorses in New Zealand. Methods: Horses (n=171) in active training for racing by trainers (n=24) located throughout New Zealand were examined using gastroscopy during 2003 and 2004. Images of the examination were recorded and reviewed, and an ordinal grade based on the severity of gastric ulceration present was assigned, using the grading system proposed by the Equine Gastric Ulcer Council (EGUC). Information about the horses such as age, breed, sex, stabling, time at pasture, pasture qu...
Sykes BW, Sykes KM, Hallowell GD.Studies on omeprazole have reported that doses as low as 0.7 mg/kg bwt per os are potent suppressors of acid production. Yet, to date, no studies have compared treatment efficacy of different doses in clinical cases of equine gastric ulceration. Furthermore, no studies have been performed to compare the healing response of the squamous and glandular mucosa to acid suppression therapy. Objective: To compare: 1) the efficacy of 2 doses of omeprazole in the treatment of primary squamous and glandular gastric ulceration; and 2) the healing response of primary squamous and glandular gastric ulcer...
Lane EA, Bijnen ML, Osborne M, More SJ, Henderson IS, Duffy P, Crowe MA.To evaluate factors contributing to fertility of thoroughbred mares, data from 3743 oestrous periods of 2385 mares were collected on a large thoroughbred farm in Ireland. Fourteen stallions (mean age 8.3 years; range 4-15 years) had bred 2385 mares (mean age 9.4 years; range 3-24 years). Maiden mares accounted for 12%, mares with a foal at foot for 64%, and barren, slipped or rested mares for 24% of the total. The mean pregnancy rate per cycle was 67.8% (68.6% in year 1 and 66.9% in year 2). Backward stepwise multivariable logistic regression analysis was utilized to develop two models to eval...
Powell DG, Watkins KL, Li PH, Shortridge KF.Equine-2 influenza virus A (H3N8) infection occurred among vaccinated thoroughbred horses in Hong Kong during November and December 1992. The outbreak was unique in that it occurred among a large population stabled under intensive conditions. It resulted in the postponement of seven race meetings over a period of 32 days. The outbreak originated after the importation of horses 25 to 32 days before any clinical signs were reported. Vaccination did not prevent 75 per cent of the population from becoming infected, and half the infected horses developed clinical signs. Vaccination did, however, co...
Snow DH, Harris RC, Gash SP.Four thoroughbred horses performed 4 gallops (G1-G4) with intervals of 5 min. With one exception, gallops were sustained at maximal speed over 620 m. Muscle biopsy samples of the middle gluteal and brachiocephalicus were taken before, during, and after exercise and assayed for ATP and intermediary metabolites. The results showed a major involvement of the brachiocephalicus, in addition to the middle gluteal, during galloping. In three horses, who were clearly fatigued, muscle ATP decreased by up to 50% by the end of G4. This was matched by an equal rise in inosine 5'-monophosphate. Pronounced ...
Nath LC, Anderson GA, McKinnon AO.To evaluate the reproductive efficiency of horse farms in north-east Victoria and identify aspects of management to be targeted for improving reproductive efficiency. Methods: Retrospective study. Methods: Records from seven Thoroughbred (TB) and four Standardbred (STB) studs in north-east Victoria from 1990 to 2001 were reviewed; 8813 cycles in 4455 mares were analysed. TB mares were inseminated by natural mating, whereas STB mares (89%) were artificially inseminated. Results: The overall early pregnancy rate per cycle was 68.8% for TB mares and for STB mares, 68.3%. Multiple pregnancy per cy...
Riggs CM, Whitehouse GH, Boyde A.This study examined 3-dimensional (3D) distribution of sectors with contrasting density in the equine third metacarpal (McIII) and third metatarsal (MtIII) bones with a view to explaining the aetiology of distal condylar fractures. Macroradiography and computed tomographic (CT) imaging were used in the nondestructive study of bones obtained from horses, most of which were Thoroughbreds in race training. Distal condylar regions of McIII and MtIII were also studied in microradiographs of 100 microm thick mediolateral sections cut perpendicular to the dorsal and palmar/plantar articular surfaces....
Boyde A, Riggs CM, Bushby AJ, McDermott B, Pinchbeck GL, Clegg PD.Arthropathy of the distal articular surfaces of the third metacarpal (Mc3) and metatarsal (Mt3) bones in the Thoroughbred racehorse (Tb) is a natural model of repetitive overload arthrosis. We describe a novel pathology that affects the articular calcified cartilage (ACC) and subchondral bone (SCB) and which is associated with hyaline articular cartilage degeneration. Parasagittal slices cut from the palmar quadrant of the distal condyles of the left Mc3/Mt3 of 39 trained Tbs euthanized for welfare reasons were imaged by point projection microradiography, and backscattered electron (BSE) scann...
Austin SM, Foreman JH, Hungerford LL.Risk factors for development of pleuropneumonia were determined by reviewing medical records of 45 horses with pleuropneumonia and 180 control horses examined between Jan 1, 1980 and Jan 1, 1990. Factors considered included age, breed, sex, occupation, transport farther than 500 miles within the previous week, racing within the previous 48 hours, viral respiratory tract infection or exposure to horses with viral respiratory tract disease within the previous 2 weeks, and vaccination against influenza or rhinopneumonitis within the previous 6 months. Results indicated that Thoroughbreds were at ...
Kitaoka Y, Masuda H, Mukai K, Hiraga A, Takemasa T, Hatta H.The aim of this study was to investigate the effects of training and detraining on the monocarboxylate transporter (MCT) 1 and MCT4 levels in the gluteus medius muscle of Thoroughbred horses. Twelve Thoroughbred horses were used for the analysis. For 18 weeks, all the horses underwent high-intensity training (HIT), with running at 90-110% maximal oxygen consumption (VO2 max ) for 3 min, 5 days week(-1). Thereafter, the horses either underwent detraining for 6 weeks by either 3 min of moderate-intensity training (MIT) at 70% VO2 max, 5 days week(-1) (HIT-MIT group) or stall rest (HIT-SR group)....
Love EJ, Taylor PM, Murrell J, Whay HR.To investigate the antinociceptive effects of buprenorphine administered in combination with acepromazine in horses and to establish an effective dose for use in a clinical environment. Objective: To evaluate the responses to thermal and mechanical stimulation following administration of 3 doses of buprenorphine compared to positive (butorphanol) and negative (glucose) controls. Methods: Observer blinded, randomised, crossover design using 6 Thoroughbred geldings (3-10 years, 500-560 kg). Thermal and mechanical nociceptive thresholds were measured 3 times at 15 min intervals. Horses then rec...
McCue PM, Ferris RA.An understanding of the normal events of foaling, causes of dystocia and clinical outcomes is important for equine practitioners. Objective: The goals of the present study were to: 1) evaluate factors that influence gestation length; 2) report duration of Stage II labour; 3) determine the frequency of dystocia and premature placental separation; and 4) determine the relationship between problems at foaling and foal survival. Methods: Foaling records of 1047 mare births were evaluated. Results: The average gestation length was 342.7 days [corrected] +/- 0.4 days, with no effect of mare age or b...
Gilkerson JR, Whalley JM, Drummer HE, Studdert MJ, Love DN.Sero-epidemiological studies conducted between 1995 and 1997 on two large Thoroughbred stud farms in the Hunter Valley of NSW showed clear evidence of EHV-1 infection in foals as young as 30 days of age. Similarly, serological evidence suggested that these foals were infected with EHV-1 from their dams or from other lactating mares in the group, with subsequent foal to foal spread of infection prior to weaning. These studies also provided evidence of EHV-1 infection of foals at and subsequent to weaning, with foal to foal spread of EHV-1 amongst the weanlings. These data indicated that the mar...
