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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.
Arthroscopic surgery for subchondral cystic lesions of the medial femoral condyle in horses: 41 cases (1988-1991). Clinical signs, radiographic and arthroscopic findings, and outcome for 41 horses with subchondral cystic lesions of the medial femoral condyle treated by arthroscopic surgery were reviewed. There were 17. Quarter Horses, 15 Arabians, 8 Thoroughbreds, and 1 Holsteiner, with 28 (68%) of the horses being 1 to 3 years old. For all horses, the owners' complaint was mild to moderate hind limb lameness or an altered gait. Bilateral radiographic abnormalities of the medial femoral condyle were detected in 27 horses. Nineteen of the 27 horses had lesions identified bilaterally at arthroscopic surgery....
Trace mineral supplementation of yearling horses. Thirty-three Thoroughbred and Quarter Horse yearlings were used in two experiments (18 in Exp. 1 and 15 in Exp. 2) to determine the influence of trace mineral (TM) supplementation on growth and bone mineral content in young growing horses from 340 to 452 d of age. In each experiment the yearlings were assigned at random within breed and sex outcome groups to one of three treatments. Horses were fed assigned concentrates individually to appetite for two 1.5-h feeding periods, daily and group-fed Coastal bermudagrass (Cynodon dactylon) hay in drylot paddocks at a rate of 1.0 kg/100 kg BW daily. ...
[American Quarter Horses and HYPP]. Hyperkalaemic periodic paralysis is a genetic disease that affects the American Quarter Horse population and is caused by a mutation. As a result of this mutation in a gene which codes for the sodium channel in muscle cells, severe muscle weakness can appear. Reliable DNA-tests can establish whether a horse is homozygous negative, heterozygous, or homozygous positive for this mutation. Therapy and prevention are discussed.
Cauda equina syndrome, diskospondylitis, and a paravertebral abscess caused by Rhodococcus equi in a foal. A 4-month-old male Quarter Horse was referred for evaluation of urinary incontinence. Physical examination revealed clinical signs consistent with cauda equina syndrome. Radiography revealed diskospondylitis of S2 through S4. Infected bone was surgically curretted, and drainage was established for an associated paravertebral abscess. Rhodococcus equi was isolated from specimens of bone and from fluid samples obtained from the paravertebral abscess. Bethanechol was administered to stimulate urination. Erythromycin and rifampin were administered for 120 days. The foal's neurologic dysfunction re...
Ultrasonographic morphology of the bicipital tendon and bursa in clinically normal quarter horses. The bicipital tendons and bursae of 25 healthy adult Quarter Horses were ultrasonographically examined. Cross-sectional images of the right and left bicipital tendons were obtained from each horse, using a 7.5-MHz transducer held in the frontal plane at the point of the shoulder. The bicipital tendon at the point of the shoulder appeared as a bilobate structure overlying the echogenic surface of the humerus. Median distance from the skin surface to the cranial surface of the tendon on the medial sagittal plane of the tendon was 23 mm (range, 16.5 to 30 mm); median distance on the lateral sagit...
Eosinophilic keratoconjunctivitis in a horse. An 11-year-old Quarter Horse gelding was evaluated because of a persistent, raised band of 1- to 2-mm subepithelial plaques of the left cornea. Cytologic examination of corneal scrapings revealed numerous eosinophils and segmented neutrophils, with few mast cells, plasma cells, and lymphocytes. Bacteriologic culture yielded sparse growth of alpha-hemolytic Streptococcus and Staphylococcus spp. Histologically, the plaques consisted of subepithelial foci of fragmented and degenerated collagen fibers infiltrated by eosinophils and neutrophils, with few lymphocytes, plasma cells, and macrophages. ...
Lead foreign body arthropathy in a horse. A diagnosis of degenerative joint disease secondary to an intra-articular metallic foreign body in the right metacarpophalangeal joint was made in a Quarter Horse gelding. Arthroscopy, performed to evaluate the joint and remove the foreign body, revealed yellow discoloration of the articular cartilage and synovium, and blunting and proliferation of the synovium. The foreign body was identified as a lead sphere. Microscopic examination of synovium revealed chronic synovitis, with accumulation of hemosiderin and multifocal, mild mineralization. Another pigment was evident extracellularly in the ...
Equine motor neuron disease: findings in 28 horses and proposal of a pathophysiological mechanism for the disease. Over a three and one-half year period, 28 adult horses were diagnosed with equine motor neuron disease (EMND). The most commonly identified environmental risk factors for a horse having EMND were absence of grazing for more than a year and provision of poor quality hay. Quarter Horses were 5.4 times more at risk than other breeds but this was thought to be an epiphenomenon related to the frequency of Quarter Horses at boarding stables. Weight loss, excessive recumbency and/or trembling were the first signs noted. Other clinical diagnostic signs included: constant shifting of the weight in the ...
Proximodorsal first phalanx osteochondral chip fragmentation in 336 horses. The results of arthroscopic surgery in the treatment of osteochondral fragmentation of the proximodorsal aspect of the first phalanx and the influence of other fetlock joint lesions on prognosis were evaluated in 336 horses. Horses were classified as: 1) returning to previous use at the same or higher class of performance; 2) returning to previous use (regardless of class of performance); or 3) failing to return to previous use. Ninety-six horses (29%) had fragmentation alone; 140 horses (42%) had fragmentation and additional fetlock lesions, and 100 horses (29%) underwent concurrent carpal ar...
Haematological, bone marrow and clinical chemical changes in neonatal foals given canine recombinant granulocyte-colony stimulating factor. Five Thoroughbred and Quarter Horse cross foals were given 20 micrograms canine recombinant granulocyte-colony stimulating factor (rcG-CSF) per kg bwt intramuscularly (i.m.) on the day of birth and 10 micrograms rcG-CSF/kg for 13 additional days. During this time and for an additional 21 days haematology, bone marrow and clinical chemical analyses were performed. After one day of rcG-CSF administration leucocyte and neutrophil counts increased from 9.16 x 10(9)/l to 23.44 x 10(9)/l and from 6.45 x 10(9)/l to 19.61 x 10(9)/l, respectively. The counts continued to increase for the next 3-4 days ...
Causes of death in racehorses over a 2 year period. Necropsies were performed on 496 horses that had a fatal injury or illness at a California racetrack during the period February 20th 1990 to March 1st 1992. The primary cause of death was categorised by breed, activity at time of injury or illness and organ system affected. Most of the submissions were Thoroughbred horses (432) and Quarter Horses (46). Most of the injuries occurred while racing (42%) and in training sessions (39%); with fewer non-exercise (12%) and accident (7%) related injuries or illnesses. Musculoskeletal injuries accounted for 83% of the Thoroughbred and 80% of the Quarter...
Maternal influences on growth and development of full-sibling foals. Six pairs of full-sibling Quarter Horse foals were produced by non-surgical embryo transfer and immediate rebreeding of donor mares. Each pair of donor/recipient mares consisted of one multiparous (donor) and one nulliparous (recipient) mare of similar body type and size. Milk yield was determined within 2 d of 8, 15, 22, 29 d (early lactation); 45, 60 d (midlactation); and 90, 120 d (late lactation) postpartum by the weigh-suckle-weigh method. On the following day, milk samples were collected, and foals were weighed and measured for wither height, heart girth, metacarpal length, metatarsal le...
Serum hepatitis in two brood mares. Two adult Quarter Horse mares from the same farm developed signs of hepatic disease approximately 2 months after parturition. Both mares had received tetanus antitoxin at the time of foaling. One mare developed subcutaneous edema of the distal aspect of all 4 limbs, photodermatitis involving unpigmented areas of skin, and high serum activities of liver-specific enzymes. The other mare had signs of acute hepatic failure, including icterus, hepatic encephalopathy, and high serum activities of liver-specific enzymes, and died. The second mare had signs typical of serum hepatitis (Theiler's diseas...
Mucinous hyperplasia in the kidney and ureter of a horse. A case of mucinous hyperplasia in the right renal pelvis and ureter is reported in a 23-year-old, male, Quarter horse. The affected right renal pelvis was markedly distended and filled with inspissated yellowish-green mucous material compressing the adjacent cortical and medullary parenchyma. Multiple, similar masses were present protruding from the right urethral mucosa. Histologically, the masses were characterized by a cystic glandular and papillary hyperplasia of the mucosa of the renal pelvis and ureter. This is believed to be the first reported case in an equine species.
Selection of quarter horses affected with hyperkalemic periodic paralysis by show judges. Thirty offspring of a Quarter Horse sire, affected by hyperkalemic periodic paralysis (HPP), were examined electromyographically. On the basis of the detection of or lack of spontaneous activity with high frequency myotonic or pseudomyotonic discharges, the horses were diagnosed as being affected (14 horses) or unaffected (16 horses) with HPP. The show performance of these horses was evaluated for the first 3 to 9 years of their life by use of American Quarter Horse Association records. Horses affected with HPP performed significantly (P < 0.01) better in halter classes than did unaffected ...
The effect of supplemental lysine and threonine on growth and development of yearling horses. Thirty-nine Thoroughbred and Quarter Horse yearlings were used in two 112-d experiments to determine the effect of lysine and threonine supplementation on growth and development. Yearlings were individually fed three dietary treatments that consisted of a pelleted concentrate containing corn, oats, and soybean meal fed to appetite twice daily and Coastal bermuda grass hay group-fed at a rate of 1 kg/100 kg BW. Three concentrates were tested: (A) basal, (B) basal plus .2% lysine, and (C) basal plus .2% lysine, and .1% threonine. Feed intake, weight, withers height, girth, hip height, body lengt...
Epidemiology of equine motor neuron disease. Equine motor neuron disease (EMND) is a newly recognized neurodegenerative disorder of bulbospinal motor neurons in the horse. We conducted a case-control study to identify intrinsic factors associated with the risk of this disorder. Seventy-four cases and 160 controls were assembled. Controls included horses diagnosed with equine protozoal myelitis, equine degenerative myeloencephalopathy, and cervical stenotic myelopathy during the same time period as the cases. Logistic regression analysis was used to evaluate the association of each hypothesized factor while simultaneously controlling for ...
Rheological characteristics of horse blood: significance during exercise. When horses maximally exercise, splenic contraction and fluid movement out of the vascular compartment greatly increase the hematocrit (up to 0.70). We studied the in vitro rheological characteristics of blood from Thoroughbreds and Quarter Horses to determine the interaction of hematocrit and shear rate on apparent viscosity. We also compared the rheological characteristics of the blood before and after horses received furosemide, a drug commonly used to prevent exercise-induced pulmonary hemorrhage. Although the apparent viscosity of blood with a high hematocrit was high at low shear rates, ...
[HYPP–hyperkalemic periodic paralysis in horses]. A literature review of the clinical syndrome HYPP (Hyperkalemic periodic paralysis) affecting Quarter Horses is given. HYPP is characterized by sporadic attacks of muscle tremors, weakness and/or collapse, lasting for variable periods of time. Diagnosis is based on physical findings in association with hyperkalemia. In horses with HYPP, the regulation of ion transport through the sodium channels in the muscle cells occasionally fails, causing uncontrollable muscle twitching. Further investigations into molecular genetics reveals a mutation in the gene responsible for sodium and potassium regul...
The effect of added dietary soybean oil on vitamin E status of the horse. Fourteen 2-yr-old Quarter Horses and Quarter Horse x Thoroughbreds were randomly assigned to either a control (CTRL) diet or a diet supplemented with 6.4% soybean oil (SBO). The amounts of both diets that were fed met current NRC nutrient requirements and were isoenergetic with similar nutrient:energy ratios. Venous blood samples (20 mL) were taken at d 0, 30, 60, and 90 of the experiment and analyzed for serum alpha-tocopherol, serum cholesterol, and serum triglyceride. The sum of serum cholesterol and serum triglyceride values was used as an estimate of serum total lipid. The ratio of serum ...
Adrenal insufficiency associated with long-term anabolic steroid administration in a horse. Adrenal insufficiency was diagnosed in a 9-year-old American Quarter Horse gelding that had received monthly injections of stanozolol for 8 years. After the injections were abruptly discontinued, the horse developed anorexia, lethargy, weight loss, and bilateral forelimb lameness. Secondary hypoadrenocorticism was diagnosed on the basis of clinical signs, lack of high endogenous plasma ACTH concentration, and lack of cortisol response to administration of ACTH. Because the medical history did not include glucocorticoid administration, the cause was determined to be excessive administration of ...
Palmar digital neurectomy in horses. 57 cases (1984-1990). The medical records of 57 horses that had palmar digital neurectomy performed between 1984 and 1990 were reviewed. Neurectomies were performed either by transection and electrocoagulation (47 horses) or by the guillotine technique (10 horses). Middle-aged geldings, Quarter Horses, and Thoroughbreds were significantly over-represented when compared with the hospital population. Horses used as hunter/jumpers also appeared to be over-represented. Complications occurred in 17 (34%) of the 50 horses for which follow-up information was obtained. Recurrence of heel pain was the most common complicati...
[3H]ouabain binding in skeletal muscle from horses with hyperkalemic periodic paralysis. Ouabain, a cardiac glycoside, binds to the Na(+)-K(+)-adenosine triphosphatase (Na+ pump) and prevents active transport of Na+ and K+ across cell membranes. We used [3H]ouabain to quantify the number and affinity of Na+ pumps in skeletal muscle from Quarter Horses with the muscular disorder hyperkalemic periodic paralysis (HYPP). [3H]Ouabain-binding properties of gluteal muscle from clinically normal and affected horses were used to determine whether altered Na+ pump number or affinity could contribute to the pathologic features of muscle in affected horses. Foals and adult horses with HYPP we...
Clinical syndrome and diagnosis of hyperkalaemic periodic paralysis in quarter horses. Of the 16 horses studied, 14 belonged to a family previously shown to be susceptible to hyperkalaemic periodic paralysis (HPP), and 8 were shown to have HPP. Diagnosis of HPP by electromyographic detection of myotonic discharges or by oral administration of KCl to induce clinical signs and hyperkalaemia had similar reliability and gave the same result in 80% of cases. KCl had to be administered at doses up to 0.2 g/kg bodyweight to produce signs in some horses. KCl challenge testing was more time consuming than EMG and resulted in one fatality. Overall, electromyography and potassium challenge...
Risk factors associated with equine motor neuron disease: a possible model for human MND. Equine motor neuron disease (EMND), a newly described neurodegenerative disease, bears a striking resemblance to progressive muscular atrophy (PMA) in humans. We present a comparison of the equine and human diseases and the results of a case-control study conducted to identify intrinsic factors associated with EMND. Cases included all horses with a confirmed diagnosis of EMND diagnosed in the United States since 1985 (32 cases). Controls included horses diagnosed with either cervical stenotic myelopathy, equine degenerative myeloencephalopathy, or protozoan myelitis at the Veterinary Teaching ...
