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Topic:Quarter Horses

Quarter Horses are a distinct breed of horse known for their versatility, agility, and speed over short distances. Originating in the United States, they are particularly noted for their performance in sprinting races, such as the quarter-mile, from which their name is derived. Quarter Horses are characterized by their muscular build, broad chest, and powerful hindquarters, which contribute to their exceptional acceleration and maneuverability. These traits make them popular in various equestrian disciplines, including rodeo events, ranch work, and western riding competitions. This page compiles peer-reviewed research studies and scholarly articles that explore the genetics, physiology, and performance characteristics of Quarter Horses, as well as their role in equine sports and industry.
Icterus in a 3-day-old Quarter Horse foal.
Journal of the American Veterinary Medical Association    August 26, 2026   1-3 doi: 10.2460/javma.26.06.0489
Lewis E, Badial P.No abstract available
Musculoskeletal examination of the hind limb of the horse.
Journal of the American Veterinary Medical Association    August 7, 2026   1 doi: 10.2460/javma.26.03.0234
Kamm JL, Odegaard J, Mogannam B.The intention of this tutorial video is to illustrate the methods of examining the hind limb and back of a horse in order to identify abnormalities that may be associated with lameness or disease. Unassigned: An 18-year-old quarter horse stallion was used for examination. Unassigned: The horse was examined for abnormalities using physical examination. Unassigned: The examination of the hind limb and epaxial region of the horse was successfully completed. Unassigned: The techniques described are required to identify abnormalities in the equine hind limb and can be utilized during a lameness exa...
Seroprevalence, risk factors and hematological parameters associated with Equine Infectious Anemia from Casanare, Colombia.
Journal of equine veterinary science    August 3, 2026   106108 doi: 10.1016/j.jevs.2026.106108
Puentes MMM, Guzman YL, Torreglosa JCT, Isaza PAL, Guzman-Barragán BL.Equine infectious anemia (EIA) is a persistent lentiviral disease with important sanitary and economic implications in tropical regions; however, epidemiological information in Colombia remains limited. Objective: To estimate seroprevalence, identify risk factors, and evaluate hematological alterations associated with EIA in horses from Casanare, Colombia. Methods: A cross-sectional study including 1,228 horses from 204 production units across 121 rural districts. Serological diagnosis was performed using agar gel immunodiffusion. Demographic and management data were obtained through an epidem...
Efficiency of transvaginal oocyte aspiration (TVA), post-mortem ovary harvest (OH), and Intracytoplasmic Sperm Injection (ICSI) in a Quarter Horse mare population in North America.
Theriogenology    July 27, 2026   Volume 265 118111 doi: 10.1016/j.theriogenology.2026.118111
Ramírez-Agámez L, Love CC, Hernández-Avilés C.In a clinical setting, Intracytoplasmic Sperm Injection (ICSI)-derived equine blastocysts can be obtained either by transvaginal oocyte aspiration (TVA) or post-mortem ovary harvest (OH). Most peer-reviewed retrospective reports have described the suitability of these techniques for obtaining blastocysts, pregnancies, and live foals, particularly in Warmblood horse populations in Europe. In this study, retrospective data from Quarter Horse client-owned mares subjected to TVA-ICSI (n = 105; 151 cycles) or OH-ICSI (n = 42) at an academic institution in North America between 2023 and 2025...
Phenotypic Definition Influences Genetic Inference and Predictive Ability for Reining Performance in Quarter Horses Using Random Regression Models.
Animal science journal = Nihon chikusan Gakkaiho    July 23, 2026   Volume 97, Issue 1 e70223 doi: 10.1111/asj.70223
Santana ML, Bignardi AB.Reining performance is influenced by subjectivity and competition structure, challenging genetic evaluation. This study estimated genetic parameters for reining performance in Brazilian Quarter Horses using random regression models (RRM) and evaluated how alternative phenotypic definitions affect genetic inference and predictive ability. A dataset comprising 21,165 longitudinal records from 1603 horses was analyzed, comparing within-group rank (RANK) and Blom-transformed rank (BLOM). Model comparison indicated that cubic RRM provided the best fit for both phenotypes. Heritability estimates wer...
When genes meet money: Genotype-by-prize interaction in Quarter Horses.
Journal of equine veterinary science    July 8, 2026   Volume 166 106081 doi: 10.1016/j.jevs.2026.106081
Santana ML, Bignardi AB.Barrel racing performance reflects a complex interplay among genetic merit, rider ability, training strategies, and competition-specific conditions. In practice, events differ substantially in their economic scale, and prize money can serve as a proxy for management intensity, rider expertise, and selection pressure. Objective: This study investigated whether economic stratification, represented by total prize money per event, is associated with changes in (co)variance components for barrel racing time in Brazilian Quarter Horses. Methods: A reaction-norm model was implemented using 349,262 ra...
Genetic Indicators of Performance Resilience in Barrel Racing Quarter Horses.
Animal genetics    July 7, 2026   Volume 57, Issue 4 e70158 doi: 10.1002/age.70158
Santana ML, Bignardi AB.Resilience, defined as the capacity to maintain consistent performance under variable conditions, has emerged as a relevant breeding objective in livestock systems, yet remains largely unexplored in equine populations. The objectives of this study were to (1) derive indicators of resilience from longitudinal barrel racing time (BRT) records in Brazilian Quarter Horses, (2) estimate genetic parameters for these indicators, and (3) quantify their genetic relationships with BRT and accumulated career earnings (ACE). The dataset comprised BRT records from barrel racing events held between 2010 and...
Cutaneous Equine Sarcoidosis: A Case Series and Investigation Into a Potential Association With Equine Gammaherpesviruses-2 and -5 in 30 Equids.
Veterinary dermatology    July 3, 2026   doi: 10.1111/vde.70101
Garandeau C, Champion CP, Lejeune M, Peters-Kennedy J.Gammaherpesviruses have been associated with granulomatous inflammation in the skin of various species. Equine sarcoidosis (idiopathic granulomatous disease) can cause granulomatous dermatitis, and its cause remains unknown. Objective: This retrospective study aimed to investigate the possible association between equine gammaherpesviruses-2 and -5 (EHV-2, -5) and cutaneous equine sarcoidosis (cES). Methods: Thirty client-owned equids. Methods: All animals had histologically and clinically confirmed cES. Signalment, geographical location and clinical features were recorded. Gram, Ziehl-Nielsen ...
Short-term provision of moderate dietary starch alters fecal microbiota but does not exacerbate exercise-induced inflammation in yearling Quarter Horses.
Journal of equine veterinary science    June 27, 2026   106071 doi: 10.1016/j.jevs.2026.106071
DiSilvestro AN, Wesolowski LT, Williams BD, Warren LK, Athrey G, White-Springer SH.Energy-dense feeds commonly provided to equine athletes may be high in starch, which alter gastrointestinal microbiota and could promote systemic inflammation. Objective: To test the hypothesis that exercise-induced inflammation would be greater in horses receiving a starch- versus fiber-based concentrate. Methods: Quarter Horses (mean±SD 16±1mo; 337±30kg) received either a fiber-based control (CON; 7 fillies, 8 geldings) or an isocaloric, isonitrogenous starch concentrate (STARCH; 8 fillies, 7 geldings) for 24d. Fecal metagenomics were evaluated on d0 and 21. Blood inflammatory mediators w...
Similar locomotor patterns across Quarter Horse disciplines inform lameness assessment.
Equine veterinary journal    June 12, 2026   doi: 10.1002/evj.70213
de Siqueira RF, Brito LA, de Figueiredo IM, Dos Santos ACR, Dos Anjos LS.Lineage-based selection is central to the Quarter Horse industry and is often justified by the assumption that morphology determines locomotor function. However, objective evidence linking static conformation to discipline-specific locomotor behaviour under standardised conditions remains limited. Objective: To investigate whether morphological differences among Quarter Horse disciplines are associated with distinct locomotor patterns or whether locomotor function converges across disciplines despite morphological variation. Methods: Cross-sectional. Methods: Barrel racing, reining, and ranch ...
Thermal Thresholds and Genetic Sensitivity in Barrel Racing Performance of Quarter Horses Across Temperature-Humidity Indices. Santana ML, Bignardi AB.Heat stress is an increasingly important challenge for the performance and welfare of equine athletes, particularly in competitions conducted across diverse climatic conditions. Understanding the genetic basis of performance responses to increasing thermal load is therefore essential to support robust genetic evaluation and sustainable selection strategies. The objective of this study was to evaluate barrel racing performance of Brazilian Quarter Horses across thermal environments defined by two widely used indicators, the temperature-humidity index (THI) and the wet bulb globe temperature (WB...
Association Between Vaquejada Practice and Biomarkers of Oxidative Stress, Inflammation, and Muscle Damage in Quarter Horses.
Veterinary sciences    May 29, 2026   Volume 13, Issue 6 531 doi: 10.3390/vetsci13060531
Nascimento RCMD, Guedes EAB, Silva RBD, Cerqueira ITI, Freire CCDS, Câmara DR, Moura FA, Escodro PB, Goulart MOF.Vaquejada (VQ) is a traditional Brazilian sport demanding high performance from Quarter Horse (QH) athletes. This study aimed to identify modifications in hematological, biochemical, inflammatory, and oxidative stress biomarkers associated with VQ training, comparing conditioned and non-conditioned horses. Blood samples were collected at rest from 70 healthy QH horses: 60 athletes (VQ-conditioned athlete group-AG) and 10 sedentary controls (breeding horses-CG). Using Linear Mixed Models alongside comprehensive hematological and biochemical analyses, the study found that AG horses exhibited an ...
Clodronate disodium reduced TRAP5b independent of affecting other systemic biomarkers of bone resorption or formation in yearling, exercising Quarter Horses.
Journal of animal science    April 29, 2026   skag135 doi: 10.1093/jas/skag135
Paris BL, Leatherwood JL, Arnold CE, Glass KG, Conrad MB, George JM, Martinez RE, Colbath AC, Nielsen BD, Welsh TH, Bradbery AN.Clodronate disodium (CD), a bisphosphonate, modulates bone metabolism. Though extra-label use in juvenile horses is anecdotally reported, impacts on skeletal development are unknown. The objective was to determine the effects of CD on systemic markers of bone turnover in yearling horses undergoing exercise, hypothesizing that biomarkers of bone resorption would decrease while biomarkers of bone formation would not change, and that repeat CD treatments would have greater effect. To test this, 32 yearling Quarter Horses were used in a 168-d trial. Horses were stratified by age (500 ± 13 d),...
The incidence of fatal and non-fatal injury in thoroughbred and Quarter Horse racehorses in Louisiana (2014-2022).
Research in veterinary science    April 27, 2026   Volume 207 106219 doi: 10.1016/j.rvsc.2026.106219
Dirikolu L, Liu CC, Schaeffer DJ.The objectives of the study were to report the incidence of race-related injuries and equine fatalities in racehorses at the Louisiana racetracks from 2014 to 2022 for both Thoroughbred and Quarter Horse racehorses. Additionally, this study evaluated several factors that may be related to the occurrence of race-related injuries in racehorses in Louisiana. The average rates of equine fatal injuries (euthanized on or off track within 72 h of the race) were 1.70 ± 0.76 and 1.94 ± 0.89 per 1000 starts in Thoroughbred and Quarter racehorses, respectively. The average rates of non-fatal injur...
HERDA-associated variant in bull-catching (vaquejada) Brazilian Northeastern bull-catching Quarter Horses.
Journal of equine veterinary science    April 11, 2026   105892 doi: 10.1016/j.jevs.2026.105892
Caceres AM, Sperandio LMS, Alvarenga NACA, Borges AS, Oliveira-Filho JP.Bull-catching (vaquejada) accounting for approximately 13% of sport horses in Brazil. Genetic screening has enabled strategies to reduce the spread of inherited disorders, including Hereditary Equine Regional Dermal Asthenia (HERDA), a major skin disease included in the Six Panel required for registration by the Brazilian Quarter Horse Breeders Association. Although the HERDA-associated variant has been extensively studied in other disciplines, it had not been evaluated in Bull-catching Quarter Horses (QH). Objective: The present study aimed to determine the allele frequency of the pathogenic ...
Successful Use of Vincristine in a Quarter Horse Gelding with Immune-Mediated Thrombocytopenia.
Journal of equine veterinary science    April 8, 2026   105889 doi: 10.1016/j.jevs.2026.105889
Salewski KE, Talavera MA, Gonzalez GA, Waldridge BM, White JM, Williams MJ, Williams ML.This case reports the successful use of vincristine in a Quarter Horse with presumed immune-mediated thrombocytopenia. A 15-year-old Quarter Horse gelding presented for a pinch skin graft procedure on the left forelimb over the cannon bone. On day 10 of hospitalization, the horse developed a fever (102.6°F, RI: 99-101°F), and severe petechiae of the mucous membranes. A complete blood count (CBC) (Advia 2120i) revealed a severe thrombocytopenia (16,000 platelets/μL, RI:100,000-400,000/μL). Diagnostic testing was negative for Anaplasma phagocytophilum by PCR, Theileria equi and Babesia cabal...
Histological properties of the distal sesamoidean impar ligament in racing Thoroughbreds and Quarter horses. Faramarzi B, Lee D, Khamas W, Dong F.The distal sesamoidean impar ligament (DSIL) is a key component of the equine podotrochlear apparatus, yet its role in conditions such as caudal heel pain and navicular syndrome remains poorly understood. The objective of this study was to characterize the histological properties of the DSIL and evaluate how it is influenced by breed and age. Eighty-four cadaveric forelimb DSIL samples were collected from young, athletic Quarter horses (QHs), Thoroughbreds (TBs), and older, retired Quarter horses. Samples were stained and assessed for vessel size and count, number of nerve fascicles, and the r...
Caudal esophageal achalasia in a Quarter Horse colt.
Journal of veterinary internal medicine    March 29, 2026   Volume 40, Issue 2 aalag053 doi: 10.1093/jvimsj/aalag053
Alvarado Soto GJ, Maldonado M, Armentrout A, Woolard K, Aleman M, Giaretta P, Willis AT.Achalasia is the most common motility disorder of the esophagus in humans and has been diagnosed in cats and dogs. We describe a 4-month-old Quarter Horse colt with failure to thrive, recurrent colic episodes, and aspiration pneumonia, in which fluoroscopic evaluation identified a caudal esophageal motility disorder consistent with achalasia. Necropsy examination confirmed achalasia.
Assessment of baseline adrenocorticotropic hormone and insulin concentrations in healthy horses in Saskatchewan over a 1-year period.
Journal of veterinary internal medicine    February 26, 2026   Volume 40, Issue 1 aalaf056 doi: 10.1093/jvimsj/aalaf056
Viviani P, Ragno VM, Parker S, Montgomery JB.Endocrine disorders in horses, such as pituitary pars intermedia dysfunction and equine metabolic syndrome, rely on hormone testing for diagnosis, but seasonal and regional variabilities highlight the need for locally generated data. Objective: To characterize monthly blood concentrations of ACTH and insulin over 1 year in healthy horses in Saskatchewan. A secondary objective was to assess the association between these outcomes and the following factors: sex, age, breed, pregnancy status, level of exercise, body condition score, and cresty neck score. Methods: Sixty-eight clinically healthy, c...
Widespread Osteolysis as an Uncommon Manifestation of Equine Sarcoidosis. DiBello D, Cassel N, Granacka V, Beard L, Rosado SC, Hill-Thimmesch K, Avellar H.Equine sarcoidosis is an uncommon disease characterized by granulomatous inflammation presenting in a spectrum of body system involvement and severity. Musculoskeletal manifestations are sporadically reported but without correlation between imaging and pathologic findings. In a mature Quarter Horse mare eventually diagnosed with a progressive form of sarcoidosis, phalangeal osteolysis discovered on radiography prompted further evaluation, revealing diffuse, discrete osteolysis throughout the axial skeleton. Due to disease progression, humane euthanasia was elected, and computed tomography and ...
Genetic and phenotypic insights into thermal load and racing performance of Quarter Horses.
Journal of thermal biology    December 29, 2025   Volume 136 104362 doi: 10.1016/j.jtherbio.2025.104362
Santana ML, Bignardi AB, Faria RAS, Silva JAIV.Thermal load is a major welfare and performance concern for athletic horses, as physical exertion increases internal heat production. Although several phenotypic strategies have been developed to mitigate its effects, the genetic basis of thermal tolerance in horses remains largely unexplored. This study aimed to (1) evaluate the influence of thermal indices on the racing performance of Brazilian Quarter Horses, and (2) investigate the genetic basis of thermal tolerance through the estimation of genetic parameters across temperature gradients. We analyzed 21,857 racing-time (RT) records from 5...
Salivary cortisol concentration in western performance horses and riders: Associations with performance.
Journal of equine veterinary science    November 20, 2025   Volume 156 105737 doi: 10.1016/j.jevs.2025.105737
Pennington MV, Zoller JL, White-Springer SH, Harlin JF, Huseman CJ, Leatherwood JL, O'Reilly CL.Competition stress is a common factor influencing the success of performing athletes. However, few studies have quantified the physiological stress responses in horses and riders surrounding an equestrian event. Objective: The objectives of the current study were to determine salivary cortisol concentrations (SCC) as an indicator of stress in fifteen horse and rider pairs competing in western stock horse events and to investigate the relationship between SCC and performance. Methods: Subjects included male and female Quarter horses aged 3-15 years and equestrians aged 18-22 years. Salivary sam...
Rapidly increasing abdominal profile in a multiparous pregnant Quarter Horse mare.
Journal of the American Veterinary Medical Association    November 19, 2025   Volume 264, Issue 3 354-356 doi: 10.2460/javma.25.09.0590
Pasch LR.No abstract available
Effects of clodronate disodium on markers of inflammation and cartilage metabolism in juvenile horses challenged with intra-articular lipopolysaccharide.
Journal of animal science    November 12, 2025   Volume 103 skaf393 doi: 10.1093/jas/skaf393
George JM, Leatherwood JL, Paris BL, Arnold CE, Glass KG, Conrad MB, Martinez RE, Vergara-Hernandez FB, Nielsen BD, Colbath AC, Welsh TH, Bradbery AN.Perceived chondroprotective and anti-inflammatory benefits of bisphosphonates in the juvenile horse has led to extra-label use without supportive data regarding intra-articular effects on cartilage metabolism and inflammation. Thirty-two yearling Quarter Horses were stratified into 4 treatment groups by age (500 ± 13 d), BW (336 ± 26 kg), sex (n = 16 female; n = 16 male) and initial bone optical density for a 140-d study. The study consisted of two exercise phases: Phase 1 (d 0-84) emulated sales preparation and Phase 2 (d 99-140) mimicked early exercise training. Horses we...
Cryptorchidism in Equid: A Retrospective Study on Diagnostic Approach, Anaesthesia Management, Surgical Treatment and Outcomes.
Animals : an open access journal from MDPI    October 9, 2025   Volume 15, Issue 19 2923 doi: 10.3390/ani15192923
Nocera I, Moroni R, Fanelli D, Rota A, Di Franco C, Ungari C, Puccinelli C, Gandini M, Giusto G, Vannozzi I.Over the years, various diagnostic and surgical techniques have been developed to recognise and treat cryptorchidism in equid. This study retrospectively analysed cases of cryptorchidism referred to two centres between 2012 and 2025. Clinical data collected included species, breed, age, gender, location of retained testis, diagnostic approach, anaesthesia plan and surgical treatment, perioperative medical treatment, intra-operative complications and outcomes. A total of 37 clinical cases were included, 1/37 was a donkey and 1/37 was an intersex female. Most of the horses were three years old a...
Extraskeletal chondroma of the tongue in a two-year-old quarter horse colt: a case report.
Veterinary research communications    September 29, 2025   Volume 49, Issue 6 334 doi: 10.1007/s11259-025-10918-2
Ralletti MV, Meistro F, Tarasconi MA, Mandrioli L, Renzi A, Rinnovati R, Spadari A.Extraskeletal chondromas (ESCs) are rare benign tumours composed of mature cartilage that typically develop in soft tissues. Their occurrence in horses is extremely uncommon and, to the authors' knowledge, no previous cases of lingual ESCs in equines have been reported. This report describes a two-year-old Quarter Horse colt presented with progressive dysphagia. Clinical examination revealed a solitary, multilobulated, firm-elastic mass located at the dorsal aboral portion (base) of the tongue. Diagnostic imaging ruled out bone involvement. The mass was surgically excised under general anaesth...
Evaluation of the Effectiveness of Single-Nucleotide Polymorphisms Versus Microsatellites for Parentage Verification in Horse Breeds.
Veterinary sciences    September 15, 2025   Volume 12, Issue 9 890 doi: 10.3390/vetsci12090890
Kim D, Lee S, Oyungerel B, Cho G.This study aimed to generate information for parentage testing in horse breeds using microsatellites (STRs) and single-nucleotide polymorphisms (SNPs). Genotype data were obtained from 189 horse hair root samples, including 38 Thoroughbreds (TBs), 17 Jeju horses (JHs), 20 Quarter horses (QHs), 21 American Miniatures (AMs), and 93 Mongolian horses (MHs), using 15 STR markers and 71 SNP markers. Comparative analysis revealed that the mean expected heterozygosity ranged from 0.468 (AM) to 0.491 (JH) for SNPs and from 0.695 (TB) to 0.791 (MH) for STRs. The mean observed heterozygosity ranged from ...
Reference Values and Association of Body Weight, Age, and Sex With Echocardiographic Measurements in Non-Athletic Quarter Horses.
Journal of veterinary internal medicine    September 11, 2025   Volume 39, Issue 5 e70237 doi: 10.1111/jvim.70237
Selecky ME, Louie EW, Donnelly C, Finno CJ, Morgan JM.Background: Echocardiographic reference intervals for Quarter Horses are infrequently reported.Objectives: To provide standard echocardiographic measurements for sedentary Quarter Horses and evaluate the relationship between physical characteristics (body weight, age, sex) and echocardiographic measurements.AnimalsForty-one sedentary Quarter Horses, free of cardiac disease, from a university research herd.Methods: A cross-sectional study evaluating standardized echocardiograms performed on sedentary Quarter Horses (41) between 2020 and 2022. Reference intervals were calculated for raw and weig...
Equine Sarcoid Arising From the Medial Caruncle With Invasion of the Third Eyelid in a Quarter Horse Gelding.
Veterinary ophthalmology    September 4, 2025   Volume 29, Issue 2 e70074 doi: 10.1111/vop.70074
Plotsker NM, Taylor R, Coffin HR, Beatty A, Newbold G, Knickelbein KE.To describe the clinical and histologic features of a sarcoid arising from the medial caruncle with spread to the third eyelid of a horse. Methods: A 20-year-old Quarter Horse gelding. Methods: An incisional biopsy of the medial caruncle mass was initially performed, with histopathology suggesting a sarcoid or other spindle cell neoplasm. The mass grew rapidly following the biopsy, expanding to affect the third eyelid and adjacent superior palpebral conjunctiva. A complete third eyelid and medial caruncle excision with resection of affected palpebral conjunctiva and adjunctive cryotherapy was ...
Retrospective Evaluation of Cryptorchid Sidedness at Colorado State University Between 1984 and 2014 and Oakridge Equine Hospital Between 2008 and 2023.
Veterinary sciences    August 23, 2025   Volume 12, Issue 9 796 doi: 10.3390/vetsci12090796
Fain H, Hendrickson DA, Buesing MT, Griffenhagen G.Cryptorchidism is a common congenital disorder in male horses characterized by the failure of one or both testes to descend into the scrotum. This developmental anomaly has important clinical, surgical, and economic implications, particularly in breeding animals. This retrospective study investigates the prevalence and laterality of cryptorchidism in a large equine population presented to two veterinary referral hospitals-Colorado State University Veterinary Teaching Hospital (CSU VTH, 1984-2014) and Oakridge Equine Hospital (OEH, 2008-2023). Medical records were reviewed to identify affected ...
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