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Topic:Clinical Study
Clinical studies in equine research involve the systematic investigation of health and disease in horses through structured scientific methods. These studies aim to evaluate the safety and efficacy of treatments, understand disease mechanisms, and improve veterinary care practices. Clinical studies can include randomized controlled trials, observational studies, and case-control studies. They may focus on various aspects such as pharmacokinetics, therapeutic interventions, and diagnostic techniques. This page compiles peer-reviewed research studies and scholarly articles that explore the design, implementation, and findings of clinical studies in equine medicine, providing insights into their impact on horse health and veterinary practices.
Role of hilar nerve afferents in hyperpnea of exercise. The objective of this study was to determine the role of hilar nerve (lung vagal) afferents in the hyperpnea of exercise. Ten ponies were studied before and 2-4 wk and 3-12 mo after sectioning only the hilar branches of the vagus nerves (HND). After HND, lung volume feedback to the medullary centers was attenuated as indicated in the anesthetized state by 1) attenuation or absence of the Hering-Breuer inflation reflex (P less than 0.01) and 2) attenuation of the lengthened inspiratory time (TI) when the airway was occluded at end expiration (P less than 0.01). Moreover, after HND in the awake ...
Inherited nuclear cataracts in the Morgan horse. Congenital cataracts affecting the fetal and embryonal lens nucleus were found in 12 Morgan horses. Ten of the 12 affected animals were sired by the same stallion and the condition also affected his female half sibling. Although females were almost three times more likely to be affected than males (9 vs 3), the difference was not significant. The ratio of 11 normal to 10 affected offspring by the affected stallion is compatible with an autosomal dominant mode of inheritance.
High resolution R-bands produced in equine chromosomes after incorporation of bromodeoxyuridine. Cell synchronization was used to obtain an adequate percentage of very long chromosomes in equine mitotic spreads. Reported here is our variation, adapted to horse chromosomes, of a method using excess thymidine followed by bromodeoxyuridine incorporation. This technique routinely yields excellent quality cells, predominantly in prometaphase and prophase. Among other differences with the standard technique, this method does not use Colcemid, which, in addition to inhibiting spindle fiber formation, also increases chromosome contraction resulting in thicker and thus fewer bands. Consequently, h...
Some dynamic and toxic effects of theophylline in horses. A single intravenous administration of theophylline as aminophylline at 10 mg/kg to four mares induced a diuresis in which maximal urine production was more than seven times the control volume. The diuretic effect was maximal within the first hour post-administration, and lasted approximately 6 h. Theophylline resulted in dose-related tachycardia, polypnoea and nervous symptoms (tactile, visual and auditory hypersensitivity, muscle tremor, sweating) in normal mares, but had only minor effects on arterial and central venous blood pressures, intrapleural pressure, red blood cell variables and pl...
Equine whole saliva: variability of some major constituents. Whole saliva was collected from six horses over a period of five weeks in sufficient volume for the analysis of 10 constituents. There was considerable variation in the concentration of the analytes both between horses and between different days in the same horse. The most variable constituent was sodium, and the least variable was glucose, but this was derived from the sweet used to stimulate salivation. The use of whole saliva as a fluid for investigation would depend on achieving the minimum variability possible.
Disposition of sulfadimidine and its N4-acetyl and hydroxy metabolites in horse plasma. The plasma disposition of sulfadimidine (SDM) and its metabolites N4-acetylsulfadimidine (N4-SDM), 6-hydroxymethyl-4-methyl-pyrimidine (SCH2OH) and 5-hydroxy-4,6-dimethyl-pyrimidine (SOH), was studied in three horses following intravenous administration of SDM at dose levels of 20 and 200 mg/kg in cross-over trials. The percentages of N4-SDM (0.58-0.90%), SOH (0.83-6.75%) and SCH2OH (0.38-0.71%) in plasma, expressed as a percentage of the total sulfonamide concentration, were small and their plasma concentrations were parallel with SDM from 4 h following administration. At high doses (200 mg/k...
Incorporation of L-75Se-cystine in tissue fragments from the matrix of the hoof and the claw–a tool for studying the pathogenesis of laminitis? An in vitro method has been designed and used to study the incorporation of 75Se-cystine into matrix fragments from hooves and claws of healthy horses and cattle. Tissue fragments from the zone of keratinisation were incubated with L-75Se-cystine in a tissue culture medium for 4 to 6 h, during which time there was continuous incorporation of the labelled selenocystine. The incorporation was greatly decreased by adding L-cystine to the incubation mixture. It is concluded that the incorporation of 75Se-cystine depends on the presence of a specific receptor for cystine in the tissue fragments stu...
Unusual response following use of succinylcholine in a horse anesthetized with halothane. A syndrome similar to malignant hyperthermia developed in a 545-kg Quarter Horse while anesthetized with halothane for cataract removal. Succinylcholine administration caused prolonged, severe muscle fasciculations followed by tachycardia, and an elevated blood pressure. Later, while the horse was still under anesthesia, its body temperature rose 2 degrees C, and respiratory acidosis developed. Myositis developed after surgery, but the horse recovered.
The influence of dietary selenium levels on blood levels of selenium and glutathione peroxidase activity in the horse. Twenty mature geldings, averaging 535 kg, were used to determine the influence of dietary selenium (Se) on the blood levels of Se and Se-dependent glutathione peroxidase (SeGSH-Px) activity in the horse. Horses were randomly assigned within breed to four treatments consisting of five horses each and fed a basal diet containing .06 ppm of naturally occurring Se. Diets were supplemented with .05, .10 and .20 ppm Se, as sodium selenite. Blood was drawn for 2 wk before, and for 12 wk following, the inclusion of supplement Se in the diets. Whole blood and plasma Se concentrations and plasma SeGSH-P...
Total intravenous anaesthesia in the horse with propofol. The use of propofol, solubilised in a non-ionic emulsifying agent, for the induction and maintenance of anaesthesia in experimental ponies was assessed. Pilot studies revealed that premedication with xylazine (0.5 mg/kg bodyweight [bwt]) intravenously (iv) followed by propofol (2.0 mg/kg bwt) iv provided a satisfactory smooth induction. Two infusion rates (0.15 mg/kg bwt/min and 0.2 mg/kg bwt/min) were compared for maintenance of anaesthesia. An infusion rate of 0.2 mg/kg/min produced adequate anaesthesia in these ponies. Cardiovascular changes included a decrease in arterial pressure and card...
Causative ehrlichial organisms in Potomac horse fever. An ehrlichia was consistently isolated from the peripheral blood leukocyte fraction of ponies that had been experimentally infected with Potomac horse fever by whole blood transfusion from naturally infected horses. The organism was propagated in a human histiocyte cell line for 3 to 5 weeks and then inoculated intravenously or intradermally into healthy adult ponies. Clinical signs of Potomac horse fever, which varied in the degree of severity, occurred 9 to 14 days post-inoculation in all of the ponies. One pony died 20 days post-inoculation. The ehrlichial organism was reisolated in the hum...
Equine blood serum calcium and phosphorus concentrations in progressive nutritional hyperparathyroidism. Weekly blood serum samples from 20 yearling horses, divided into equal groups, receiving diets with total calcium to inorganic phosphorus ratios of 1,5/1 and 0,2/1, were analysed for calcium and phosphorus concentrations. This was done over a continuous 23 week period, divided into 2 sub-periods of 16 and 7 weeks each. During the first period complete diets were provided ad lib but were restricted during the second period to accentuate any effects of calcium deficiency and phosphorus excess. Falling calcium levels and rising phosphorus levels during period 1 and a reverse trend during period 2...
Diagnostic value of contrast echocardiography in the horse. M-mode echocardiography is a safe and practical means of using ultrasound to evaluate the dynamic movements of cardiac structures. The technique can be refined by using a simple contrast medium in the form of carbon dioxide mixed with heparinised blood to provide a strong echogenic result. This technique was employed in a series of 15 normal conscious standing horses and in three animals with specific cardiac defects. In the clinical cases it was possible to confirm the diagnosis and differentiate between a congenital septal defect and mitral regurgitation. The method was found to be safe and ...
Cardiovascular and respiratory effects of acetylpromazine and xylazine on halothane-anesthetized horses. Circulatory and respiratory effects of intravenously administered acetylpromazine (0.033 and 0.067 mg/kg) and xylazine (0.5 and 1.0 mg/kg) were studied in drug cross-over fashion in eight laterally recumbent horses anesthetized only with halothane (1.06%, end-tidal) in O2. Both doses of acetylpromazine caused a significant and sustained elevation in cardiac output via a rise in stroke volume. Xylazine produced an initial significant fall in cardiac output followed by a return to control levels. Halothane anesthesia did not prevent xylazine-related atrioventricular conduction block. All treatme...
Phagocytic and killing capacities of uterine-derived polymorphonuclear leukocytes from mares resistant and susceptible to chronic endometritis. The host defense competence of uterine-derived polymorphonuclear leukocytes (PMN) from mares considered resistant (grade I uteri) and susceptible (grade III uteri) to chronic endometritis was evaluated for phagocytic and killing (bactericidal) capacities, using a fluorochrome assay. Peripheral blood PMN from noncategorized mares and from grade I and grade III mares were used as controls. Uterine-derived PMN from mares with grade I uteri were functionally competent for phagocytosis and killing of Candida albicans, whereas uterine-derived PMN from mares with grade III uteri had significantly les...
Transendoscopic electrosurgery for epiglottal entrapment in the horse. Monopolar electrosurgical cutting was used to correct epiglottal entrapment in 5 horses. The operations were carried out in the conscious animal, using topical anesthesia. The procedure required the use of a coagulation electrode designed specifically for electrosurgery, introduced through the instrument channel of a fiberoptic endoscope. The results were satisfactory and serious complications were not encountered. In 2 horses, excessive submucosal swelling developed at the site of the surgical wound, and the tumefaction took several weeks to subside in one of these horses. In both horses, the...
Combined pharmacokinetics of gentamicin in pony mares after a single intravenous and intramuscular administration. Healthy mature pony mares (n = 6) were given a single dose of gentamicin (5 mg/kg of body weight) IV or IM 8 days apart. Venous blood samples were collected at 0, 5, 10, 20, 30, and 45 minutes and at 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 18, 24, 30, 36, 40, and 48 hours after IV injection of gentamicin, and at 10, 20, 30, and 45 minutes and at 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 18, 24, and 30 hours after IM injection of gentamicin. Gentamicin serum concentration was determined by a liquid-phase radioimmunoassay. The combined data of IV and IM treatments were analyzed by a nonlinear least-square...
In vivo bone strain in the equine tibia before and after transection of the peroneus tertius muscle. The present study was undertaken to determine the influence of the peroneus tertius muscle on the loading regime of the tibia in the horse. Strain gauge rosettes were bonded to the cranial and caudal cortices of the left and right tibiae in six Shetland ponies. In vivo bone strain recordings were made before and after unilateral transection of the peroneus tertius muscle. Relatively large individual variations in response to transection were observed in both the experimental and the contralateral control limbs. The principal strain values on the cranial and caudal cortices increased during the...
Cefadroxil in the horse: pharmacokinetics and in vitro antibacterial activity. Sodium cefadroxil was administered as a single intravenous dose (25 mg/kg) to six healthy adult mares. Plasma samples were collected over a 24-h period and cefadroxil concentrations were measured by microbiological assay. The pharmacokinetic behavior of the drug was appropriately described in terms of a one-compartment open model. Values for the major pharmacokinetic terms were: extrapolated initial plasma concentration = 59.2 +/- 15.0 micrograms/ml; half-life = 46 +/- 20 min; apparent volume of distribution = 462 +/- 191 ml/kg; and body clearance = 7.0 +/- 0.6 ml/min.kg. In a subsequent study...
A hemodynamic model for anaphylactic shock. The treatment of cardiovascular collapse and anaphylactic shock is largely empiric. A simple animal model was developed to evaluate the hemodynamic alterations in anaphylaxis. Eight adult New Zealand white rabbits of both sexes were studied. All animals weighed 3.8 kg to 5.3 kg. Sensitization was accomplished with a 2-mL subcutaneous dose of horse serum followed in two days with a 2-mL intravenous (IV) dose. At least 14 days elapsed after the IV dose before a 1-mL challenge dose of horse serum was given. On the day of the challenge dose, a femoral arterial catheter, arterial temperature probe,...
Comparison of echocardiographic and autopsy measurements of cardiac dimensions in the horse. This study was initiated to determine the accuracy of M-mode echocardiography in measuring left ventricular dimensions and estimating heart weights in horses. Left ventricular free wall and interventricular septal thickness and left ventricular external and internal diameters were measured and heart weights estimated from the echocardiograms of 47 horses. Autopsy measurements of the same parameters were then recorded. Statistical comparison of the data demonstrated: (1) Systolic measurements of wall thickness more closely resembled the heart in death than the diastolic measurements; (2) good c...
Efficacy of furosemide in the treatment of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses. The repeatability of endoscopic observations of exercise-induced pulmonary hemorrhage (EIPH) and the efficacy of furosemide as a prophylactic treatment of horses with EIPH were studied in Thoroughbred race horses after consecutive breezes (at or near maximum speed, approx 16 m/s). Of 56 horses examined greater than or equal to 2 times, 21 (38%) had identical EIPH scores, whereas 26 (46%) and 9 (16%) had scores that differed by greater than or equal to 1 grade. In 56 nontreated horses, there was good agreement between 2 consecutive observations (K = 0.59, Z = 4.54, P less than 0.001). Similar c...
Diagnostic radiology and nuclear cardiology. Their use in assessment of equine cardiovascular disease. Survey thoracic radiography, although limited by physical considerations in the adult horse, can supply clinically useful information about changes in cardiac size and function. The radiographic features of cardiomegaly, altered pulmonary circulation, pulmonary edema, and pleural effusion as manifested in the horse are discussed. Nuclear cardiology can be performed in the standing horse. The initial transit of a radioactive tracer through the central circulation provides information about cardiac chamber size, efficiency of ventricular contraction, valvular competence, and presence of intracar...
Use of cancellous bone graft in treatment of navicular bone osteomyelitis in a foal. 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...
The use of the glutaraldehyde coagulation test for detection of hypogammaglobulinaemia in neonatal foals. The effectiveness of the glutaraldehyde coagulation test (GCT) in detecting failure to acquire colostral immunoglobulin in neonatal foals was investigated. This was achieved by comparing and correlating results from the GCT with those obtained by single radial immunodiffusion (SRID) of equine IgG. The GCT was found to be a practical, inexpensive, semiquantitative test with a high specificity and sensitivity at critical IgG levels.
Pharmacokinetics of small doses of 3-methylindole given to horses. The pharmacokinetics of 3-methylindole (3MI) given orally in 2 doses (10 mg/kg and 20 mg/kg) to horses were determined. The pharmacokinetic plasma-concentration profiles for 3MI (10- and 20-mg/kg dosages) in horses were represented by a 2-compartment open model with first-order absorption, as determined by nonlinear least-squares regression analysis. Absorption of 3MI at both dosages was rapid. Comparisons of the peak plasma concentrations, the postdistribution half lives, total clearances, and areas under the curve of the plasma-concentration profiles between the 10- and the 20-mg/kg dosages ...
Salmonella shed by horses with colic. Salmonella was isolated from 13 of 100 colicky horses admitted to a referral hospital. Seven horses were shedding the microorganism at or soon after hospital admission. A unique serotype was introduced into the hospital by a horse not shedding Salmonella at admission. It was concluded that 8 horses were infected before admission. Whether the remaining 5 horses were infected before or after admission could not be determined. Salmonella senftenberg was the most commonly isolated serotype from colicky horses and from horses with salmonellosis that were not colicky on hospital admission during the...
Effect of diuresis on urinary excretion and creatinine clearance in the horse. Endogenous creatinine clearance and renal excretion of phenylbutazone, osmotically active material, and compounds contributing to the urinary refractive index were studied in 12 Thoroughbred mares after no treatment, after water administration, or after furosemide administration. Urine was quantitatively collected, using urinary bladder catheters. On average, urine flow of the mares was 9 microliters/min/kg without treatment and increased to about 50 microliters/min/kg after water administration and to about 70 microliters/min/kg after furosemide administration. Water administration increased ...
