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.
Successful treatment of a sinonasal cryptococcal granuloma in a horse. A 12-year-old 500-kg (1,100-lb) American Quarter Horse mare was evaluated because of chronic mucopurulent, bloody discharge from the left nostril, inspiratory dyspnea, and respiratory noise. Results: The horse had severe inspiratory dyspnea and stertorous respiration with no airflow from the left nostril. A temporary tracheostomy was performed. Endoscopy revealed a tan mass protruding from the left middle nasal meatus into the left common nasal meatus; it extended caudally into the nasopharynx and around the caudal edge of the nasal septum into the right nasal cavity. Radiographically, a soft ...
Malignant hyperthermia associated with ryanodine receptor 1 (C7360G) mutation in Quarter Horses. Anesthetic-induced malignant hyperthermia (MH) has been documented in Quarter Horses with a single point mutation in the ryanodine receptor 1 gene (RyR1) at nucleotide C7360G, generating a R2454G amino acid substitution. However, there have been no reports of nonanesthetic manifestations of MH in horses with the C7360G mutation. Objective: To describe clinical manifestations of Quarter Horses with the C7360G mutation. Methods: Eleven Quarter Horses with the RyR1 C7360G mutation. Methods: This prospective study included horses with suspected MH, undetermined etiology of sudden death, death with...
Evaluation of allele frequencies of inherited disease genes in subgroups of American Quarter Horses. To estimate allele frequencies of the hyperkalaemic periodic paralysis (HYPP), lethal white foal syndrome (LWFS), glycogen branching enzyme deficiency (GBED), hereditary equine regional dermal asthenia (HERDA), and type 1 polysaccharide storage myopathy (PSSM) genes in elite performance subgroups of American Quarter Horses (AQHs). Methods: Prospective genetic survey. Methods: 651 elite performance AQHs, 200 control AQHs, and 180 control American Paint Horses (APHs). Methods: Elite performance AQHs successful in 7 competitive disciplines (barrel racing, cutting, halter, racing, reining, western...
Effects of changing body position on oxygenation and arterial blood pressures in foals anesthetized with guaifenesin, ketamine, and xylazine. To investigate the impact of a change in body position on blood gases and arterial blood pressures in foals anesthetized with guaifenesin, ketamine, and xylazine. Methods: Prospective, randomized experimental study. Methods: Twelve Quarter Horse foals, age of 5.4 +/-0.9 months and weighing 222 +/- 48 kg. Methods: Foals were anesthetized with guaifenesin, ketamine, and xylazine for 40 minutes in lateral recumbency and then assigned to a change in lateral recumbency after hoisting (Group 1, n = 6), or no change (Group 2, n = 6). Oxygen 15 L minute(-1) was insufflated into the endotracheal tube t...
Polysaccharide storage myopathy phenotype in quarter horse-related breeds is modified by the presence of an RYR1 mutation. In this study we examined a family of Quarter Horses with Polysaccharide Storage Myopathy (PSSM) with a dominant mutation in the skeletal muscle glycogen synthase (GYS1) gene. A subset of horses within this family had a more severe and occasionally fatal PSSM phenotype. The purpose of this study was to identify a modifying gene(s) for the severe clinical phenotype. A genetic association analysis was used to identify RYR1 as a candidate modifying gene. A rare, known equine RYR1 mutation, associated with malignant hyperthermia (MH), was found to segregate in this GYS1 PSSM family. Retrospective ...
Associations of sex, breed, and age with cervical vertebral compressive myelopathy in horses: 811 cases (1974-2007). To determine sex, breed, and age distributions in a population of horses with cervical vertebral compressive myelopathy (CVCM), compared with contemporaneous control horses. Methods: Retrospective case-control study. Methods: 811 horses with CVCM and 805 control horses. Methods: The Veterinary Medical Database was searched to identify horses with CVCM and contemporaneous control horses registered between July 1974 and August 2007. Admission date, admitting institution, sex, breed, age at the time of registration in the database, weight, and discharge status (alive, died, or euthanized) were re...
A GYS1 gene mutation is highly associated with polysaccharide storage myopathy in Cob Normand draught horses. Glycogen storage diseases or glycogenoses are inherited diseases caused by abnormalities of enzymes that regulate the synthesis or degradation of glycogen. Deleterious mutations in many genes of the glyco(geno)lytic or the glycogenesis pathways can potentially cause a glycogenosis, and currently mutations in fourteen different genes are known to cause animal or human glycogenoses, resulting in myopathies and/or hepatic disorders. The genetic bases of two forms of glycogenosis are currently known in horses. A fatal neonatal polysystemic type IV glycogenosis, inherited recessively in affected Qu...
Comparison of temperature readings from a percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer in equids. To compare temperature readings from an implantable percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer, to identify factors that affect microchip readings, and to estimate the sensitivity and specificity of the microchip for fever detection. Methods: Prospective study. Methods: 52 Welsh pony foals that were 6 to 10 months old and 30 Quarter Horses that were 2 years old. Methods: Data were collected in summer, winter, and fall in groups 1 (n = 23 ponies), 2 (29 ponies), and 3 (30 Quarter Horses), respectively. Temperature readings from a digital r...
Glycogen synthase 1 (GYS1) mutation in diverse breeds with polysaccharide storage myopathy. A missense mutation in the GYS1 gene was recently described in horses with polysaccharide storage myopathy (PSSM). Objective: The first objective was to determine the prevalence of the GYS1 mutation in horses with PSSM from diverse breeds. The second objective was to determine if the prevalence of the GYS1 mutation differed between horses diagnosed with PSSM based on grade 1 (typically amylase-sensitive) or grade 2 (typically amylase-resistant) polysaccharide. Methods: Eight hundred and thirty-one PSSM horses from 36 breeds. Methods: Horses with PSSM diagnosed by histopathology of skeletal mus...
Insulin sensitivity in Belgian horses with polysaccharide storage myopathy. To determine insulin sensitivity, proportions of muscle fiber types, and activities of glycogenolytic and glycolytic enzymes in Belgians with and without polysaccharide storage myopathy (PSSM). Methods: 10 Quarter Horses (QHs) and 103 Belgians in which PSSM status had been determined. Methods: To determine insulin sensitivity, a hyperinsulinemic euglycemic clamp (HEC) technique was used in 5 Belgians with PSSM and 5 Belgians without PSSM. Insulin was infused i.v. at 3 mU/min/kg for 3 hours, and concentrations of blood glucose and plasma insulin were determined throughout. An i.v. infusion of g...
Musculoskeletal injuries in nonracing quarter horses. Quarter horses used for western performance competitions commonly sustain a variety of musculoskeletal injuries. It is important for the veterinarian to have an understanding of some of the breed characteristics and the nature of the competitions in which individual horses are being used so as to diagnose, treat, and prevent injury as effectively as possible.
Comparative anatomy and muscle architecture of selected hind limb muscles in the Quarter Horse and Arab. The Quarter Horse (bred for acceleration) and the Arab (bred for endurance) are situated at either end of the equine athletic spectrum. Studies into the form and function of the leg muscles in human sprint and endurance runners have demonstrated that differences exist in their muscle architecture. It is not known whether similar differences exist in the horse. Six Quarter Horse and six Arab fresh hind limb cadavers were dissected to gain information on the muscle mass and architecture of the following muscles: gluteus medius; biceps femoris; semitendinosus; vastus lateralis; gastrocnemius; tib...
Biochemical and genetic evaluation of the role of AMP-activated protein kinase in polysaccharide storage myopathy in Quarter Horses. To evaluate whether biochemical or genetic alterations in AMP-activated protein kinase (AMPK) play a role in the development of polysaccharide storage myopathy (PSSM) in Quarter Horses. Methods: 30 PSSM-affected and 30 unaffected (control) Quarter Horses. Methods: By use of an established peptide phosphotransfer assay, basal and maximal AMPK activities were measured in muscle biopsy samples obtained from 6 PSSM-affected and 6 control horses. In 24 PSSM-affected and 24 control horses, microsatellite markers identified from the chromosomal locations of all 7 AMPK subunit genes were genotyped wit...
Estimated prevalence of polysaccharide storage myopathy among overtly healthy Quarter Horses in the United States. To estimate the prevalence of polysaccharide storage myopathy (PSSM) among Quarter Horses in the United States and evaluate possible relationships between muscle glycogen concentration, turnout time, and exercise level. Methods: Cross-sectional study. Methods: 164 overtly healthy Quarter Horses > 2 years old from 5 states. Methods: Horses with a history of exertional rhabdomyolysis or any other muscular disease were excluded. Muscle biopsy specimens were examined histologically for evidence of PSSM and were submitted for determination of muscle glycogen concentration. A diagnosis of PSSM wa...
Confirmed and presumptive cervical vertebral compressive myelopathy in older horses: a retrospective study (1992-2004). Cervical vertebral compressive myelopathy (CVCM) is a common cause of myelopathy in horses aged 6 months to 4 years. Little information is available regarding the types of lesions, treatment, and outcomes in horses with CVCM that are > or =4 years old. Methods: Twenty-two affected horses (10 with a confirmed diagnosis of CVCM and 12 presumptive cases) and 210 contemporaneous control horses. Methods: Horses > or =4 years old that were diagnosed with CVCM between January 1992 and January 2004 were identified from medical records at Texas A&M University and the University of Florida. Data analyze...
Step ostectomy as a treatment for varus deformity of a metatarsophalangeal joint in a 4.5-month-old colt. A 4.5-month-old quarter horse colt was presented with severe right hind metatarsophalangeal varus, present since birth. On radiographs, it was determined that there was a 16 degree deviation with the pivot point at the distal physis of the 3rd metatarsal bone. A step ostectomy in the sagittal plane corrected the deformity. Un poulain Quarter horse âgé de 4,5 mois a été présenté pour une difformité congénitale métatarsophalangienne varus du membre postérieur droit. Une déviation de 16° par rapport au point de pivotement au niveau de la plaque de croissance distale du 3 métatarse a...
Genetic evaluation of performance traits in Brazilian Quarter Horse. The aim of this study was to estimate genetic parameters for racing performance traits in Quarter Horses in Brazil. The data (provided by the Sorocaba Jockey Club) came from 3 Brazilian hippodromes in 1994-2003, with 11 875 observations of race time and 7775 of the speed index (SI), distributed in 2403 and 2169 races, respectively. The variance components were estimated by the MTGSAM program, under animal models including the random additive genetic effect, random permanent environmental effect, and the fixed effects of sex, age and race. Heritabilities for race time and the SI, for the 3 dist...
Homozygosity mapping approach identifies a missense mutation in equine cyclophilin B (PPIB) associated with HERDA in the American Quarter Horse. Hereditary equine regional dermal asthenia (HERDA), a degenerative skin disease that affects the Quarter Horse breed, was localized to ECA1 by homozygosity mapping. Comparative genomics allowed the development of equine gene-specific markers which were used with a set of affected horses to detect a homozygous, identical-by-descent block spanning approximately 2.5 Mb, suggesting a recent origin for the HERDA mutation. We report a mutation in cyclophilin B (PPIB) as a novel, causal candidate gene for HERDA. A c.115G>A missense mutation in PPIB alters a glycine residue that has been conserved acr...
Endocrine profiles of periparturient mares and their foals. The aim of this study was to characterize concentrations of leptin, IGF-I, and thyroid stimulating hormone (TSH) in the blood serum of mares pre-and postpartum, in the milk serum of mares postpartum, and in the blood serum of their foals. Nine pregnant Quarter Horse mares and their offspring were used in this study. Once weekly between 1000 and 1200 h for 2 wk before their predicted parturition date, mares were weighed, assigned a BCS, and blood was sampled via jugular venipuncture. Within 2 h of parturition and before the foals nursed (d 0), blood samples were obtained from the mares and foal...
Racing speeds of quarter horses, thoroughbreds and Arabians. While Quarter Horses are recognised as the fastest breed of horse, direct comparisons to race times with other breeds can be misleading. Quarter Horse races begin when the starting gates open. Thoroughbred and Arabian races begin a short distance from the gates after horses have started running. This study compared speeds of these breeds as they accelerate from the starting gates and during the middle and end of races. Objective: To compare racing speeds of the 3 breeds, and to compare speeds during various segments of the races. Methods: Video tapes of races were obtained from a local track. ...
Prevalence of polysaccharide storage myopathy in horses with neuromuscular disorders. Controversy exists as to the prevalence of polysaccharide storage myopathy (PSSM) in breeds of horses and its impact on performance. Objective: To determine 1) the prevalence of PSSM in horses that presented with a neuromuscular disorder, as well as breed, sex and age distributions and clinical signs 2) effect of diagnostic criteria on prevalence, breed distribution and age of horses diagnosed with PSSM. Methods: Fresh frozen biopsies (n = 1426) submitted to the Neuromuscular Diagnostic Laboratory at the University of Minnesota were searched to identify horses diagnosed with PSSM. Horses with ...
Glycaemic and insulinaemic response of quarter horses to concentrates high in fat and low in soluble carbohydrates. Quarter Horses are particularly susceptible to polysaccharide storage myopathy (PSSM). Nutritional therapy and possibly prophylaxis includes fat-supplemented diets whilst starch supply should be kept to a minimum. Objective: To investigate the glycaemic and insulinaemic response of clinically normal Quarter Horses to concentrates high in fat and low in starch. Methods: Twelve Quarter Horses were studied. The precondition for inclusion in the study population was that the horses had not shown clinical signs of myopathy. The Quarter Horses were fed according to a 4 x 4 Latin square design haylag...
Induction of pulsatile secretion of leptin in horses following thyroidectomy. Endocrine characteristics of Quarter Horse-type mares were determined during a 68 h feed deprivation and again in the same mares following surgical thyroidectomy (THX). A crossover experimental design was implemented, in which mares received brome hay available ad libitum (FED) or were food deprived (RES) for 68 h. Blood samples were collected every 20 min for 48 h, beginning 20 h after the onset of food deprivation. Concentrations of triiodothyronine and thyroxine were undetectable post-THX. Plasma concentrations of thyrotropin were greater post-THX versus pre-THX (P<0 x 001). Plasma conce...
Clinical and pathological findings in a HERDA-affected foal for 1.5 years of life. A Quarter horse filly bred from two horses affected with HERDA (hereditary equine regional dermal asthenia) was observed clinically and its skin histologically for the 1.5 years of its life. Severe signs of the disease did not manifest until 1.5 years of age, and were not temporally related to saddling. Histological comparison to an age-, breed- and sex-matched control did not show any consistent diagnostic features. Monitoring of the proband substantiated previous reports of (i) the autosomal recessive nature of the disease, (ii) mares affected with HERDA being able to foal without damage to ...
Density and morphologic features of primary epidermal laminae in the feet of three-year-old racing Quarter Horses. To quantify the density of primary epidermal laminae (PELs) around the solar circumference and evaluate the relationship between regional PEL density and hoof capsule morphology in horses. Methods: Forefeet from nine 3-year-old Quarter Horse cadavers. Methods: Data pertaining to gross features of hoof morphology and PEL variables, including number, density, and distribution patterns around the perimeter of the hoof wall and number of bar PELs, were collected. Tissues of the laminar junction were examined histologically. Results: No significant differences were found between left and right fore...
Incomplete rupture of the gastrocnemius and superficial digital flexor muscles in a Quarter Horse stallion. A 16-year-old 500-kg (1,100-lb) Quarter Horse stallion was examined because of acute severe lameness involving the left hind limb. Results: Examination revealed signs of failure (concurrent flexion of the tarsus and extension of the stifle [femorotibial] joint) of the caudal component of the reciprocal apparatus. Results of radiographic evaluation ruled out fracture or joint injury as causes of the lameness. During the next 48 hours, the reciprocal apparatus on the left hind limb progressively deteriorated until the horse became non-weight bearing on the limb. Results: The horse wore a full-li...
Deep digital flexor tendon shortening as a treatment for distal interphalangeal joint hyperextension in a 2-year-old mare. Shortening of the deep digital flexor tendon was performed by tenotomy, overlapping and anastomosis. The procedure was performed on a two-year-old Quarter Horse Mare with distal interphalangeal joint hyperextension with subluxation and metatarsophalangeal joint hyperextension. These problems originated from damage to the digital flexor tendons, presumably due to previous distal limb trauma. The procedure markedly improved the mare's level of comfort, degree of ambulation and limb conformation. Two years following surgery the mare was comfortable at pasture.