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.
Cymbaluk NF, Bristol FM, Christensen DA.Plasma ceruloplasmin activities and plasma Cu and Zn concentrations were determined in 215 clinically normal equids of various ages and breeds. Newborn foals, regardless of breed, were hypocupremic, compared with adolescent and mature horses. The mean plasma Cu concentration of newborn Standardbred-Thoroughbred (STD-TB) foals was 2.9 mumol/L, which was about one-sixth of plasma Cu concentrations of mature horses. Newborn draft-cross foals had higher (4.6 mumol/L) plasma Cu concentrations than did newborn STD-TB foals, but plasma Cu content was only one-fifth of the dams' concentrations. Draft-...
Markel MD, Meagher DM, Ford TS.A 3-month-old Quarter Horse filly stepped on a fence staple and developed navicular bone osteomyelitis of the right hindfoot. A 1.5-cm spherical portion of medullary cavity containing purulent material was debrided and flushed with 0.9% NaCl solution. Cancellous bone was collected from a caudal sternebra and placed into the defect. The solar defect had filled with granulation tissue and was epithelialized 6 weeks after surgery. At 6-month follow-up evaluation, the navicular bone defect had healed and the foal was sound on the limb. Cancellous bone grafting may have merit for the treatment of n...
Hurtig MB, Farrow CS, Fretz PB.The radial carpal and intermediate carpal bones were found to be fused in a four year old Quarterhorse stallion having a subtle forelimb lameness. Clinical examination, diagnostic local anesthesia, radiography and arthroscopy were used to arrive at the diagnosis. A cause could not be established, although perinatal deformation of cartilagenous carpal bone templates is suspected. A similar case of carpal bone fusion was found among carpi collected for an anatomical study, indicating this condition may be more common than expected. Clinicians should carefully evaluate the flexed lateral view of ...
Trommershausen Bowling A, Clark RS.Gene frequencies at 20 blood group and protein polymorphism loci (A, C, D, K, P, Q, U, Al, Tf, Pi, Xk, Es, Gc, PGD, CA, Cat, PGM, AP, Hb and PHI) are given for seven horse breeds in the United States (Thoroughbred, Arabian, Standardbred, Morgan, Quarter Horse, Paso Fino and Peruvian Paso). These data are used to calculate that the battery of tests is at least 96% effective for recognizing incorrect paternity in these breeds. In addition to paternity testing, these tests can be applied to studies of breed relationships.
Magnuson NS, Perryman LE, Mason PH, Marta KM.A microassay requiring as few as 2 X 10(5) cells per assay was developed for systematic analysis of 9 purine enzymes in lymphocytes from equine peripheral blood, spleen, lymph node, thymus and bone marrow. The activities of adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), adenosine kinase (AK), deoxyadenosine kinase (dAK), deoxycytidine kinase (dCK), 5'-nucleotidase (5'-N), AMP deaminase, hypoxanthine-guanine phosphoribosyl transferase (HGPRT or HPRT), and adenine phosphoribosyl transferase (APRT) were measured by this microassay in lymphocytes from peripheral blood from four ...
Rose PL, Watkins JP, Auer JA.A comminuted, mid-diaphyseal femoral fracture was diagnosed radiographically in a 4-month-old Quarter Horse colt. Disruption of the distal blood supply was suspected, as evidenced by coolness and diminished pulses of the distal portion of the limb. The fracture was repaired by compression plating but the foal's condition continued to deteriorate. A femoral arteriogram of the affected limb was obtained. Positive contrast agent was visible only as far as the mid-shaft of the femur. The foal was euthanatized and the postmortem examination revealed a transected popliteal artery accounting for isch...
Fretz PB, Barber SM, Bailey JV, McKenzie NT.The case records of 49 horses with proximal sesamoid bone fracture were studied. The population consisted of 20 Thoroughbreds, 20 Standardbreds, 5 Quarter Horses, 2 Arabians, and 2 grade horses. The fractured bones were classified into 5 categories: apical fractures, basilar fractures, abaxial fractures, middle one-third fractures, and bilateral comminuted-distracted fractures. Apical fractures occurred most frequently in the Standardbred, with the prevalence of medial fracture being equal to that of lateral fracture. Basilar fractures occurred predominantly in the Thoroughbred, with the highe...
Fretz PB, Cymbaluk NF, Pharr JW.Long-bone growth at the distal ends of the radial bones, the distal ends of the 3rd metacarpal bones, the distal ends of the 3rd metatarsal bones, and the proximal ends of the proximal phalangeal bones (of thoracic and pelvic limbs) was quantitatively analyzed in 9 Thoroughbred-Quarter Horse foals from birth to 2 years of age. Metal growth markers were surgically implanted in the bones of the animals at 2 to 4 days of age. Radiographs of the bones were made on the day of surgical manipulation, the next day, and then once a week for 8 months, and once a month thereafter for an additional 18 mon...
Thompson DL, Honey PG.Prepubertal Quarter horse colts were immunized at 6 mo of age with either estrone-17-oxime-bovine serum albumin (n = 4; treated) or with albumin only (n = 5; controls). All colts received booster injections of the appropriate antigen at 8, 10, 12, 16 and 20 mo of age. Blood samples were drawn every 20 d from 6 to 26 mo of age; body weights were determined monthly. Immunization against estrone-albumin resulted in increased binding of [3H]-estradiol in serum within 40 d that was maintained through 24 mo of age. Antisera from treated colts crossreacted equally well with estrone and estradiol and ...
Harvey JW, Asquith RL, McNulty PK, Kivipelto J, Bauer JE.Packed cell volume, haemoglobin concentration, erythrocyte counts, erythrocyte indices, serum iron, iron binding capacities, total and differential leucocyte counts, platelet counts, total plasma protein, fibrinogen, haptoglobin and icterus index values were determined at 14 different ages in eight Thoroughbred and 14 Quarterhorse foals during the first year of life. Absolute neutrophil numbers in blood decreased and lymphocyte numbers increased during the first months. Absolute eosinophil numbers tended to increase until three months old. Haemoglobin concentration and packed cell volume decre...
Gossett KA, French DD.Serum alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), 5'nucleotidase (5'NT), sorbitol dehydrogenase (SDH), and aspartate transaminase activities were measured in 10 clinically healthy foals, 10 yearlings, and 10 two-year-old Quarter Horses. Enzyme activities in foals at 0.5 to 3 days, 2 to 3 weeks, and 5 to 7 weeks of age were compared with enzyme activities from yearling and 2-year-old horses. Multivariate analyses of variance revealed significantly higher enzyme values in foals (P less than 0.002). This increase was mainly a result of higher ALP and GGT activities, with lesser ...
Rumbaugh GE, Adamson PJ.Blood was collected from healthy Quarter Horse and Appaloosa foals at birth and at intervals until 18 weeks of age and then was processed in an automated system for serum chemical analysis, grouping the results by age. The test values were markedly different from those normally expected in adult horses. The greatest differences were in alkaline phosphatase, lactate dehydrogenase, glucose, and total bilirubin measurements. It was concluded that serum biochemical test results be compared with age-specific normal values before diagnoses are made in cases of illness.
Render JA, Harrington DD, Wells RE, Dunstan RW, Turek JJ, Boosinger TR.Giant cell tumor of soft parts was diagnosed in 6 horses 3 to 12 years old (mean, 6.8 +/- 3.5 years): 3 Quarter Horse geldings, 2 Standardbred mares, and 1 Standardbred stallion. The neoplasms developed as raised, solitary masses, approximately 1 to 4 cm in diameter, which were firmly attached to subcutaneous tissue of the neck (1 horse), shoulder (1 horse), thigh (2 horses), or stifle (2 horses). Excision was followed by local recurrence in 3 horses within 1 to 1 1/2 months. The neoplasms were firm and cut with resistance. On cut surface, they were white, with mottled red hemorrhagic areas.
Gossett KA, French DD.Anion gap [AG = (Na + K) - (Cl + HCO3)] was determined in Quarter Horses: 10 clinically normal foals 0.5 to 3 days, 2 to 3 weeks, and 5 to 7 weeks of age; 10 yearlings; and ten 2-year-olds. Mean AG (+/- 1 SD) were 12.8 +/- 3.3, 15.2 +/- 2.9, 14.0 +/- 1.6, 12.3 +/- 1.8, and 10.4 +/- 1.2 mEq/L, respectively. The 4 to 5 mEq/L higher AG in 2- to 7-week-old foals, when compared with that in 2-year-old horses, can be explained in part by hyperphosphatemia (2 mEq/L) and lower calcium values (0.4 mEq/L). Decreased globulin concentrations may also contribute to the higher AG. The AG can be useful in th...
Tunnell JA, Sanders JO, Williams JD, Potter GD.Pedigrees of randomly selected Quarter Horses born in each of the years 1946, 1956, 1966 and 1976 and of winning halter, cutting and race horses born in the same years were evaluated and compared. Average inbreeding and inter se relationship levels and relationships of influential ancestors to the sample were calculated for each sample. The amount of Thoroughbred influence and the average generation interval were also determined for each random sample. The levels of inbreeding found in the random samples were low, ranging from 1.3% in 1956 to 2.6% in 1966; however, these levels were higher tha...
Thompson DL, Reville SI, Derrick DJ.Five mature Quarterhorse mares were bled every 30 min for 25 h on day 50 of pregnancy to determine the short-term mode of secretion of equine chorionic gonadotropin (eCG). Three other mares with persistent endometrial cups after abortion were administered gonadotropin releasing hormone (GnRH; 1.0 mug/kg of body weight) and were bled immediately prior to and at 15, 30, 45, 60, 90, 120, 180 and 240 min after GnRH. Concentrations of eCG in plasma of pregnant mares were constant over the 24-h period; the variation of each mare's individual values was no greater (P>.05) than the predicted random...
Hodge SL, Kreider JL, Potter GD, Harms PG, Fleeger JL.Over a 2-year period, mares (n = 32) of predominantly Quarter Horse breeding and their foals were used to study the effects of photoperiod on reproduction during the periparturient period. Specific objectives of the study were (i) to evaluate the effects of an extended photoperiod regimen (16 hours' light) on gestation length, foal development, and postpartum reproductive performance, and (ii) to measure changes in plasma progesterone concentrations during the last trimester of gestation and plasma luteinizing hormone (LH) concentrations after foaling until ovulation. Mares in the extended day...
Ginther OJ, Douglas RH, Lawrence JR.Responses of 22 veterinarians to a questionnaire and the records of three brood-mare farms were examined to obtain information on twinning. The incidence rates of multiple ovulations on the three farms were 9%, 11%, and 22%. The multiple ovulation rate was reduced 42-67% in foaling mares compared to barren and maiden mares. Multiple ovulations were significantly more frequent in Thoroughbreds (19%) than in Quarter Horses (9%) and Appaloosas (8%). Both the questionnaire and the farm records indicated a high degree of repeatability of multiple ovulations and twin pregnancies within mares and wit...
Klem ME, Kreider JL, Harms PG, Potter GD, Kraemer DC, Godke RA.Thirty-one mares of Quarter Horse and Thoroughbred breeding were utilized in two experiments to evaluate the efficacy of prostaglandin F2 alpha (PGF2 alpha) for induction of equine parturition and to monitor the effects of this treatment on viability of the resulting foals. Three of five mares given 5 mg PGF2 alpha (im) on day 338 of gestation foaled 19.6+/-8.2 hr postinjection. In the second experiment immediately following 3 daily injections of 10 mg estradiol cypionate (ECP) given on days 326, 327 and 328 of gestation, seven mares were infused (iv) with PGF2 alpha at the rate of 1.3 mg/hr f...
Brumbaugh GW, Thomas WP, Hodge TG.A 4-year-old Quarter Horse gelding with atrial fibrillation, mitral regurgitation, and signs of bilateral congestive heart failure was initially treated IV with digoxin and furosemide. After parenteral digitalization, a daily maintenance dose of digoxin was administered orally at a rate of 21.7 micrograms/kg of body weight. At this dosage, a steady-state serum digoxin concentration of 2.3 ng/ml was achieved without clinical signs of toxicosis. The furosemide dosage was decreased and eventually discontinued as clinical improvement occurred. Clinical signs of congestive heart failure were contro...
Gibbs PG, Potter GD, Blake RW, McMullan WC.Milk production was measured in fourteen Quarter Horse mares at seven stages of a 150-d lactation period. Mares were divided into two groups of seven and fed diets containing either soybean meal or soybean meal and urea as nitrogen supplements. Rations were isocaloric, contained approximately 12.5% crude protein and were fortified with vitamins and minerals. Daily milk yield was estimated by the weigh-suckle-weigh method and milk composition was determined from samples taken by hand milking. Average daily milk yield ranged from 11.8 kg in early lactation to 9.8 kg in late lactation. Difference...
Beech J.An 18-month-old male Quarter Horse was referred for evaluation of a tic that had started after injury to the right forelimb 4 weeks earlier. The right forelimb appeared paretic and had constant regular twitches of variable intensity that were usually sufficiently forceful to move the trunk, neck, and head. The horse frequently threw the limb forward. The twitch persisted during sleep but disappeared during general anesthesia and following sedation with xylazine. It was unaffected by acetylpromazine, diphenylhydantoin, diazepam, carbamazepine, trimethadione, procainamide, quinidine, propranolol...
Ott EA, Asquith RL, Feaster JP.Forty-six Thoroughbred and Quarter Horse yearlings were used in two experiments designed to determine the amount of lysine in the concentrate necessary to promote maximum growth when fed the Coastal bermudagrass (Cynodon dactylon) hay provided at 1% body weight (BW)/day. In the first experiment, a 196-day trial, supplemental protein sources and analyses of the concentrates compared were: (1) soybean meal (SBM; 15.4% crude protein, .70% lysine); (2) SBM + .2% lysine (15.7% crude protein, .81% lysine), and (3) brewers dried grains + .2% lysine (15.9% crude protein, .59% lysine). Concentrate inta...
Heird JC, Lennon AM, Bell RW.Twenty-four yearling Quarter Horse fillies were divided into three groups (I) very limited handling, (II) intermediate handling and (III) extensive handling. At about 14 months of age, each horse was preconditioned for 2 weeks and then run in a simple place-learning T-maze test in which it had to locate its feed. Thirty trials were run daily for 20 days, with the location of the feed changed each day. To retire from the maze, a horse had to meet the criterion: 11 correct responses in 12 tries, with the last eight being consecutive. Horses in Group II required the fewest trials to reach criteri...
Chen CL, Riley AM.Serum thyroxine (T-4) and triiodothyronine (T-3) concentrations were assayed in neonatal foals (1.5 to 4 months) and mature horses (2 to 25 years old) by a modified radioimmunoassay procedure. Blood was collected from 52 clinically healthy foals and horses of various breeds (Thoroughbreds, Quarter Horses, American Saddle Horses, and a single cross-bred horse). Neonatal foals had high serum concentrations of T-4 (mean, 4.02 microgram/dl) and T-3 (192.9 ng/dl) as compared with the values in mature horses (T-4, mean of 1.76 microgram/dl; T-3, mean of 98.69 ng/dl). Stallions had slightly higher T-...
Kovár J, Kostelecká B.On the basis of test results, regarding the pulse rate response to the increased load, obtained from 278 three-year-old horses after finishing their elementary training (145 Bohemian warm-blooded horses, 115 Kladrub Black horses and 18 English half-bred horses), a method was worked for the evaluation of their performance. As an evaluating criterion a velocity (v170) was chosen which was obtained from an experimentally determined regression dependence of velocity on the pulse rate at 170 pulses per minute. A set of v170 data were statistically processed and on the basis of quantiles of normal d...
Button C, Scrutchfield WL, Clark RG, Knauer KW, Schmitz DG.A variety of atrial dysrhythmias including paroxysmal atrial tachycardia, atrial tachycardia with 2nd-grade atrioventricular block, atrial fibrillation, and atrial flutter developed in a 5-year-old Quarter Horse gelding. Quinidine and propranolol were not successful in restoring normal sinus rhythm. Sinus rhythm was re-established during digoxin therapy, but later reverted to atrial dysrhythmia. At necropsy, multiple, discrete pale areas were found on both atria and the interatrial myocardium. Histologic examination of these lesions demonstrated myocytolysis and replacement by fibrous connecti...
Stull CL, Albert WW.The percentages of three muscle fiber types in the biceps femoris and triceps brachii were determined in five breeds of horses: Belgians, Standardbreds, Thoroughbreds, Quarter Horses and Welsh ponies. Biopsies were taken from the two muscles from each of four 2-year-old untrained fillies of each breed. Percentages of red, white and intermediate fiber types were determined from tissues stained for succinic dehydrogenase activity. Intermediate fibers were the most numerous for all breeds. The difference between red and white fibers varied significantly with breed. Thoroughbreds had the highest p...
Cushing TL.A 4-year-old crossbred Quarterhorse mare was submitted to the Clemson Veterinary Diagnostic Center for necropsy examination with a chronic history of inappetence, weight loss and lethargy. Prior to death the horse had developed mild diarrhoea and began showing evidence of colic. Necropsy examination revealed a markedly enlarged heart due predominantly to marked dilation of the right atrium, tortuous congested mesenteric blood vessels, marked ascites, pleural effusion and pulmonary oedema. Further examination of the heart showed the endocardium of the left side of the heart, including the mitra...
Valberg SJ, Iglewski H, Henry ML, Schultz AE, McKenzie EC.Selective breeding and discipline specific training has led to equine breeds adept at various athletic disciplines. Breed-specific skeletal muscle adaptations have been studied in many breeds but not Warmbloods (WB). We evaluated gluteal muscle contractile muscle fiber types and citrate synthase activity (CS), a marker for mitochondrial volume density, in WB trained for dressage (second level-Grand Prix) contrasted with Quarter Horses (QH). Gluteus medius muscle biopsies from 14 unfit/18 fit dressage-trained WB and 20 unfit/16 fit reining/working cow QH were analyzed fluorometrically and fiber...
Whishaw IQ, Kolb B.A human physical asymmetry is the near 90% clockwise occipitoparietal scalp hair-whorl direction in Europeans, an incidence that approximates the left lateralization of speech and right-handedness. Hair-whorl direction is also asymmetric in horses, Equus ferus caballus and placement is proposed to be related to temperament and lateralized skill in equitation manoeuvres. We describe a hair-whorl asymmetry in the horse, mane direction. Of 526, 3-year-old American Quarter horses, 69% of horses had mane directed to the right and 31% had mane directed to the left. The bias was larger in females, wi...
Kovár J, Kostelecká B.On the basis of test results, regarding the pulse rate response to the increased load, obtained from 278 three-year-old horses after finishing their elementary training (145 Bohemian warm-blooded horses, 115 Kladrub Black horses and 18 English half-bred horses), a method was worked for the evaluation of their performance. As an evaluating criterion a velocity (v170) was chosen which was obtained from an experimentally determined regression dependence of velocity on the pulse rate at 170 pulses per minute. A set of v170 data were statistically processed and on the basis of quantiles of normal d...
Knych HK, Stanley SD, McKemie DS, Steinmetz SJ.Romifidine is an alpha-2 adrenergic agonist used for sedation and analgesia in horses. As it is a prohibited substance, its purported use at low doses in performance horses necessitates further study. The primary goal of the study reported here was to describe the serum concentrations and pharmacokinetics of romifidine following low-dose administration immediately prior to exercise, utilizing a highly sensitive liquid chromatography-tandem mass spectrometry assay that is currently employed in many drug testing laboratories. An additional objective was to describe changes in heart rate and rhyt...
Jackman BR, Baxter GM, Doran RE, Allen D, Parks AH.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...
Orsini JA, Ryan WG, Carithers DS, Boston RC.To generate data on the effects of firocoxib administration to horses with osteoarthritis. Methods: Client-owned horses with signs of lameness and joint pain associated with osteoarthritis. Methods: Firocoxib was administered as an oral paste (0.1 mg/kg, q 24 h) for 14 days. Assessments were performed on day 0 (baseline) and days 7 and 14. Results: 390 of 429 horses from 80 sites in 25 states met the criteria for analysis. Quarter Horse and Thoroughbred were the 2 most commonly represented breeds, comprising half of the study population. Signs of musculoskeletal pain or lameness attributed to ...
Watson E, Davis A, Splan R, Porr CAS.With increasing public scrutiny on animal welfare, it behooves those involved in the equine industry to revisit best management practices to ensure these support healthy horses. There is little published research on how horses are used in the equine industry, particularly in therapeutic horseback riding (THR) programs. Although there is a large amount of information on the benefits of THR programs to the participants, there is little published information available about the horses. Therefore, the objective of this survey was to gather data regarding horse use and care in Professional Associat...
Janicek JC, Dabareiner RM, Honnas CM, Crabill MA.To determine clinical history, structures involved, treatment, and outcome of lacerations of the heel bulb and proximal phalangeal region (pastern) in horses. Methods: Retrospective study. Methods: 101 horses. Methods: Medical records of horses with lacerations of the heel bulb and pastern were reviewed, and follow-up information was obtained. Results: 75 horses were Quarter Horses. Most horses were not treated with antimicrobial drugs prior to referral. Mean +/- SD time from injury to referral was 24 +/- 45 hours (range, 1 to 168 hours). Lacerations were most frequently caused by contact with...
Atkins DT, Harms PG, Sorensen AM, Fleeger JL.5alpha-pregnane-3,20-dione was isolated from pooled pregnant mare serum using Sephadex LH-20 column chromatography and identified by the use of radioimmunoassay, gas-liquid chromatography and gas-liquid chromatography-mass spectrometry analyses. 5beta-pregnane-3,20-dione was not cross-reactive with the radioimmunoassay system and was not detected by gas-liquid chromatography. Peripheral blood levels of progesterone and 5alphs-pregnane-3,20-dione were determined by radioimmunoassay in four Quarter Horse mares for the first 150 days of gestation. Progesterone and 5alpha-pregnane-3,20-dione decli...
A breed known for its versatility, the American Quarter Horse (QH), is increasingly bred for performance in specific disciplines. The impact of selective breeding on the diversity and structure of the QH breed was evaluated using pedigree analysis and genome-wide SNP data from horses representing 6 performance groups (halter, western pleasure, reining, working cow, cutting, and racing). Genotype data (36 037 single nucleotide polymorphisms [SNPs]) from 36 Thoroughbreds were also evaluated with those from the 132 performing QHs to evaluate the Thoroughbred's influence on QH diversity. Results s...
Go YY, Hazard NW, Balasuriya UBR, Chapman AM, Fitton NS, Kenéz Á, Andrews FM.Accurate quantitative analysis of equine insulin in blood samples is critical for assessing hyperinsulinemia in horses. Although there are various laboratory methods for evaluating equine serum insulin, different immunoassays show significant discrepancies between the determined insulin concentrations and are often not comparable. The aim of this study was to evaluate the Immulite® 1000 chemiluminescent immunoassay (CLIA) to establish independent laboratory and assay-specific cut values to provide an accurate diagnosis of hyperinsulinemia in horses. Thus, the analytical and clinical performan...
Faria R, Vicente A, Silva J.The aim of this study was to evaluate the sprint racing performance of Quarter Horses in Brazil. Estimating genetic parameters, trends and correlations were obtained by single- and two-trait analyses using Bayesian inference (earnings to 2 years of equestrian age, best time and time class at distances of 301 m and 402 m). The data comprised a period of 38 equestrian years (1978 to 2015) with 23,482 sprint race records from 5861 animals. The heritability estimates were of low to moderate magnitude, ranging from 0.10 to 0.37 (single-trait) and from 0.15 to 0.41 (two-traits), and the repeatabilit...
Pownder SL, Caserto BG, Bowker RM, Lin B, Potter HG, Koff MF.Few noninvasive methods are available for equine hoof wall evaluation. The highly organised wall structures and composition of proteoglycans and collagens may make this region amenable to quantitative MRI (qMRI) techniques of T1ρ and T2 mapping to identify pathology related to proteoglycan content and collagen organisation respectively. Objective: To establish normative T1ρ and T2 values of the equine hoof wall of 3-year-old Quarter Horses with histological comparison. Methods: Cadaveric anatomical study. Methods: Six cadaveric left thoracic feet from 3-year-old racing Quarter Horses with no...
Meira CT, Curi RA, Farah MM, de Oliveira HN, Béltran NA, Silva JA, Mota MD.Selection of Quarter Horses for different purposes has led to the formation of lines, including racing and cutting horses. The objective of this study was to identify genomic regions divergently selected in racing line of Quarter Horses in relation to cutting line applying relative extended haplotype homozygosity (REHH) analysis, an extension of extended haplotype homozygosity (EHH) analysis, and the fixation index (F ST) statistic. A total of 188 horses of both sexes, born between 1985 and 2009 and registered at the Brazilian Association of Quarter Horse Breeders, including 120 of the racing ...
Lancaster LS, Bowker RM, Mauer WA.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...
Darby S, Porter E, Beatty SSK, Dark MJ, Smith A, Toribio RE, Gomez DE.Primary hyperparathyroidism is rare in large animal species, and little is known regarding its pathophysiology, endocrine and electrolyte derangements, diagnosis, medical management, and prognosis. This report describes the clinicopathologic diagnosis of a parathyroid (PT) gland chief cell adenoma in a 12-year-old Quarter Horse mare, including PT hormone (PTH) and electrolyte disarrangements associated with the neoplasia, the surgical removal of the adenoma, and medical management of the case. This report also describes for the first time the use PTH immunohistochemistry to confirm the nature ...
Potocnik E, Drozdzewska K, Schwarz B.We describe the case of a four-year-old Quarter Horse mare that presented with fever, respiratory infection with productive cough, disorientation, and bilateral anterior uveitis with discharge that had been previously treated with trimethoprim-sulfadiazine (TMPS). Acinetobacter johnsonii was cultured from an endoscopic tracheal wash. Treatment was initiated with cefquinome, systemic flunixin-meglumine, local ocular atropine, and corticosteroids. On subsequent days, the mare exhibited bilateral edematous, painful swelling of the face, primarily affecting the eyelids and lips. There were neither...
Pereira GL, Malheiros JM, Ospina AMT, Chardulo LAL, Curi RA.Among horses selected for speed, the racing line of Quarter Horses is characterized by high performance in sprint races, with these animals being considered the fastest horses in the world. However, few studies have investigated in more detail the polymorphisms and genes that act on this trait. The objective of this study was to analyze exomes and UTRs in regions previously associated with this trait by GWAS in Quarter Horse racehorses with contrasting maximum speed index (SImax), prospecting causal gene polymorphisms that are related to or are in strong linkage disequilibrium with racing perf...
Messer NT, Johnson PJ.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...
Goodman NL, Baker BK.Lameness problems constitute a major part of racing Quarter Horse practice. This article considers the diagnosis, prognosis, and treatment of the frequently encountered lamenesses. The main conditions included are synovitis, intra-articular fractures, osteochondritis dissecans, and degenerative joint disease as they relate to the coffin, fetlock, carpal, and tarsal joints. Intra-articular injection techniques and medications are discussed because of the frequency of joint disease. Bucked shins and stress fractures are also reviewed.
Leite RO, Ferreira JF, Araújo CET, Delfiol DJZ, Takahira RK, Borges AS, Oliveira-Filho JP.Glanzmann's thrombasthenia (GT) is an autosomal recessive inherited disorder characterized by changes in platelet aggregation, leading to hemorrhage and epistaxis. To date, two independent mutations have been described in horses and associated with this disorder, a point mutation (c.122G > C) and a 10-base-pair deletion (g.1456_1466del) in the Integrin subunit alpha2β gene (ITGA2B) of horses of different breeds (Quarter Horse, Thoroughbred, Oldenburg, and Peruvian Paso). ITGA2B codifies the αIIb subunit of the αIIbβ3 integrin, also termed platelet fibrinogen receptor. Horses with GT have b...
Yang C, Weisbrode S, Yardley J, Schroeder E, Premanandan C.Ischaemia-induced physeal injury has not been described previously in the horse. A 1-month-old Quarter horse foal was submitted for necropsy examination due to an acute onset of ataxia followed by a 4-week history of progressive decline. Focal narrowing of the spinal canal due to ventral compression by the rotation of the cranial aspect of the third cervical vertebra (C3) was observed. The metaphysis and diaphysis of C3 were markedly shortened and white-tan in colour. Microscopically, there was complete loss of the dorsal compact bone of C3 and replacement of 80% of the physis that runs parall...
Tryon RC, White SD, Famula TR, Schultheiss PC, Hamar DW, Bannasch DL.To assess heritability and mode of inheritance for hereditary equine regional dermal asthenia (HERDA) in Quarter Horses. Methods: 1,295 horses with Quarter Horse bloodlines, including 58 horses affected with HERDA. Methods: Horses were classified as affected or unaffected or as undetermined when data were insufficient to assess phenotype. Pedigree data were analyzed to determine the probable mode of inheritance. Heritability was estimated by use of Bayesian statistical methods. Results: Heritability (mean+/-SD) of HERDA was estimated to be 0.38+/-0.13, with both sexes having an equal probabili...
Aurich J, Kuhl J, Tichy A, Aurich C.Differences in the cryotolerance of spermatozoa exist among stallions, but it remains to be determined to what extent such differences are affected by breed. In this study, post-thaw semen quality in stallions presented for semen cryopreservation was analysed retrospectively (1012 ejaculates from 134 stallions of 5 breeds). The percentage of frozen-thawed ejaculates acceptable for artificial insemination (AI) and the number of insemination doses per cryopreserved ejaculate was calculated. Logistic regression analysis revealed sperm motility in raw semen as the most important explanatory variab...
Nasciutti NR, Garcia FG, da Silva ESM, de Miranda RL, Fontes LAR, Rosa JB, Headley SA, Mundim AV, Saut JPE.Several studies have demonstrated variations in peripartum blood biochemical analytes used to monitor the health status of mares and their foals of different breeds. Objective: We aimed to characterize the physiologic changes of peripartum energy and mineral metabolism in healthy Quarter Horse mares and their neonatal foals. Methods: Blood samples were initially collected from 17 mares on days 60 and 30 prepartum, and from mares and their foals on the day of parturition (after colostrum ingestion), and on days 15, 30, and 60 postpartum. The serum concentrations of calcium, phosphorus, magnesiu...
The research article describes the treatment, recovery process, and prognosis of a 2-month old Quarter Horse, who suffered from severe lameness in the left forelimb due to an avulsion-type fracture […]
Esdaile E, Knickelbein KE, Donnelly CG, Ferneding M, Motta MJ, Story BD, Avila F, Finno CJ, Gilger BC, Sandmeyer L, Thomasy S, Bellone RR.Congenital stationary night blindness (CSNB) is an ocular disorder characterized by nyctalopia. An autosomal recessive missense mutation in glutamate metabotropic receptor 6 (GRM6 c.533C>T, p.(Thr178Met)), called CSNB2, was previously identified in one Tennessee Walking Horse and predicted to reduce binding affinity of the neurotransmitter glutamate, impacting the retinal rod ON-bipolar cell signaling pathway. Thus, the first aim was to identify the allele frequency (AF) of CSNB2 in breeds with reported cases of CSNB and breeds closely related to the Tennessee Walking Horse. The second aim ...
Pfau T, Landsbergen K, Davis BL, Kenny O, Kernot N, Rochard N, Porte-Proust M, Sparks H, Takahashi Y, Toth K, Scott WM.With an increasing number of systems for quantifying lameness-related movement asymmetry, between-system comparisons under non-laboratory conditions are important for multi-centre or referral-level studies. This study compares an artificial intelligence video app to a validated inertial measurement unit (IMU) gait analysis system in a specific group of horses. Methods: Twenty-two reining Quarter horses were equipped with nine body-mounted IMUs while being videoed with a smartphone app. Both systems quantified head and pelvic movement symmetry during in-hand trot (hard/soft ground) and on the l...
