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Topic:Horses
"Horses" is a broad topic that encompasses various aspects of equine biology, behavior, and management. This category includes studies on the anatomy, physiology, and genetics of horses, as well as their behavior, nutrition, and care. Research in this area may also cover the historical and cultural significance of horses, their roles in agriculture, sport, and therapy, and the challenges associated with their conservation and welfare. The page aggregates peer-reviewed research articles and scholarly studies that explore the multifaceted relationships between humans and horses, examining both scientific and socio-economic perspectives.
In vitro phagocytosis and killing of Corynebacterium equi by alveolar macrophages of foals. Bronchoalveolar lavage was performed 5 times, sequentially, on 3 healthy foals while each foal was 6 to 63 days of age. Phagocytosis and bactericidal assays were performed on recovered alveolar macrophages. Corynebacterium equi and alveolar macrophages at a ratio of 10:1 were incubated for 1 hour in medium containing 1% heat-inactivated rabbit anti-C equi serum. After incubation, greater than 90% of the alveolar macrophages contained at least 1 ingested bacterium and each alveolar macrophage contained 9.4 +/- 1.0 bacteria (mean +/- SE). After alveolar macrophages and C equi were incubated for ...
Pharmacokinetics and bioavailability of cephalothin in horse mares. The pharmacokinetics and bioavailability of cephalothin given to 6 horse mares at a dosage level of 11 mg/kg of body weight IV or IM were investigated. The disposition of cephalothin given IV was characterized by a rapid disposition phase with a mean half-life of 2.89 minutes and a subsequent slower elimination phase with a mean half-life of only 14.7 minutes. The mean residence time of cephalothin was 10.6 +/- 2.11 minutes. The total plasma clearance of cephalothin averaged 13.6 ml/min/kg and was caused by metabolism and renal elimination. Renal clearance of cephalothin averaged 1.32 ml/min/k...
Solubilization and characterization of [3H] 5HT high affinity binding sites (5HT1 and 5HT3). The solubilization of the serotonergic 5HT1 and 5HT3 sites was performed with digitonin and sodium cholate at 1% (final concentration). Two binding sites for [3H]5HT were observed on rat or horse brain synaptosomal membranes solubilized with these detergents. The corresponding dissociation constants (KD) were 1-3 nM and 13-30 nM respectively. These values were closely similar to those corresponding to 5HT1 and 5HT3 sites located in intact membranes. The solubilized sites specifically bound 5HT. The effect of GTP decreasing the binding to 5HT1 sites was lost on solubilized 5HT1 sites; it was re...
Horse kidney neutral alpha-D-glucosidase: purification of the detergent-solubilized enzyme; comparison with the proteinase-solubilized forms. Neutral alpha-D-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) from horse kidney brush-border membranes was solubilized using Emulphogene BC 720 and purified by an affinity chromatography technique. The enzyme preparation (390-fold purified), which was free of other known microvillus hydrolases, exhibited one precipitate line in crossed immunoelectrophoresis and migrated as a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Several criteria (charge-shift crossed immunoelectrophoresis and hydrophobic chromatography) revealed the purified detergent form of t...
Retropharyngeal infections in five horses. Five horses with retropharyngeal (RP) infections had clinical signs of dysphagia and/or dyspnea. Diagnosis was confirmed, using pharyngeal endoscopy and lateral radiography of the pharynx. One horse responded to surgical drainage of a RP abscess and was sound at light work. One horse responded to medical management after the site of infection was surgically explored. Two horses recovered after medical management; the RP abscess of 1 of these 2 horses ruptured spontaneously into the pharynx and the other horse became racing sound. The fifth horse remained dysphagic and had left laryngeal hemipl...
Complexities in the denaturation of horse metmyoglobin by guanidine hydrochloride. The denaturation of horse metmyoglobin by guanidine hydrochloride was studied at pH 6.4 and 25 degrees C. Measurements of both the peptide circular dichroism and the absorbance in the Soret region suggest that the extent of renaturation strongly depends on the time interval during which the protein is exposed to concentrated solutions of the denaturant. From the equilibrium measurements of the absorption in the Soret region, it is concluded that the unfolding of metmyoglobin is complex. This is further supported by kinetic studies of denaturation which suggest the occurrence of the least four ...
Youth Accidents With Horses. In brief: In a two-year study of the estimated 13,428,000 hours of horse activities by 18,408 US Pony Clubs (USPC) members aged 6 to 21 in scheduled supervised programs, there were 64 accidents resulting in 88 injuries in 16 areas of the body. The head/face was the area most often injured (27.27%), and bruise/abrasion was the most common type of injury (28.26%). Cross-country riding was the most dangerous event (42.31%). Unexpected actions of the horse caused many accidents-25% occurred when the horse bucked and threw the rider, 23.08% when the horse refused a jump, and 17.31% when the horse f...
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...
Activities of key enzymes of aerobic and anaerobic metabolism in middle gluteal muscle from trained and untrained horses. The effect of physical training on the in vitro activities of key enzymes that provide quantitative information on the maximum capacities of anaerobic and aerobic metabolism has been investigated in the gluteal muscle of the horse. Training had no effect on the activities of 6-phosphofructokinase or creatine kinase, suggesting that there was no effect on the capacity of anaerobic metabolism in this muscle. However, the activities of hexokinase and citrate synthase were increased, indicating that training increased the capacity of aerobic metabolism. For comparative purposes, muscle fibre compo...
Arbovirus investigations in Argentina, 1977-1980. IV. Serologic surveys and sentinel equine program. Serologic surveys of wild and domestic birds, wild mammals, and horses were conducted during arbovirus field studies in Argentina from 1977 through 1980, a non-epizootic interval. The prevalence of neutralizing antibodies to eastern equine encephalitis (EEE) was consistently higher than to western equine encephalitis (WEE) virus in all species and all areas. The presence of antibodies in short-lived avian species and in young unvaccinated horses and the demonstration of seroconversions in horses during the period, indicated that these viruses are either enzootic in, or annually reintroduced in...
Cell synchronization and dynamic G-banding of equine chromosomes by bromodeoxyuridine. Both dynamic G-banding and cell synchronization produced by bromodeoxyuridine (BrdU), were applied to equine chromosomes. BrdU incorporated during the first half of the S-phase is taken up into the R-bands that are early replicating. These bands, which have incorporated BrdU, cannot contract as usual and remain elongated; only the other regions of the chromosome, i.e., the G-bands, contract normally and are sharply defined. BrdU also can be used for cell synchronization. The addition of BrdU in a high concentration, 15 hours before harvest, and its removal 11 hours later, has two effects: init...
Perirectal abscesses in six horses. Perirectal abscesses were diagnosed retrospectively in 6 horses treated for colic. The abscesses caused colic in the horses by producing an extraluminal obstruction that led to fecal impaction. The abscesses were diagnosed by rectal palpation and aspiration of exudate from the masses and were drained surgically. In horses in which the abscess involved abdominal organs, peritonitis developed.
Effects of level of dietary protein and exercise on growth rates of horses. Rates of growth were measured in two-year-old (Experiment 1) and nine-month-old (Experiment 2) horses fed high (12 or 14 per cent) or low (6 or 8 per cent) crude protein diets with one of two levels of exercise (0 or 12 km trotting per day at 12 km/h). In the non-exercised horses feed intakes and growth rates were greater on the high than on the low protein diets. Exercise increased feed intakes and growth rates of horses on the low but not the high protein diets, so that in the exercised groups there were no significant differences in feed intakes or growth rates between the horses on the two...
Periosteal transection of the proximal phalanx in foals with angular limb deformities of the metacarpo/metatarsophalangeal area. Bilateral angular limb deformities of the metacarpo/metatarsophalangeal regions in 2 foals are discussed. Periosteal transection was used to correct the deformity in both foals. In one foal, only the right forelimb was treated because the deformity in the left forelimb did not appear to warrant surgery. Subsequently, an angular limb deformity, which could have been prevented, developed in the left forelimb. A third foal developed a deformity in the proximal phalanx after periosteal transection of the distal third metatarsal bone.
Hormonal response to thyrotropin-releasing hormone in healthy horses and in horses with pituitary adenoma. Cortisol, triiodothyronine (T3), thyroxine (T4), insulin, and glucose responses to thyrotropin-releasing hormone (TRH) were evaluated in 12 healthy, mature horses and in 7 horses and 4 ponies with clinical signs of pituitary adenoma (PA). Within 1 hour after TRH administration, the increase in T3 and T4 was similar in healthy horses and animals with PA. Plasma cortisol in the group with PA increased (P less than 0.05) within 0.25 hours after TRH administration, and remained increased for 1.5 hours. In the control group, a significant increase in plasma cortisol concentrations did not develop a...
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 ...
Haemolytic crisis associated with ragwort poisoning and rail chewing in two thoroughbred fillies. Events leading to the deaths of two fillies at pasture are described. Pasture hay containing the flowering stages of Senecio jacobea (ragwort) had been fed three to four months earlier. Paddocks were subdivided with posts and rails treated with copper chrome arsenate. Six horses on the property chewed rails spasmodically. Both fillies presented with haemoglobinurea. Values in liver of 83 mg Cu kg and kidney 35 mg Cu kg wet weight and serum 1.4 mg Cu/l together with histophathology of seneciosis support a sequence of ragwort poisoning followed by copper accumulation in liver and kidney terminat...
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...
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...
Arthroscopic anatomy of the intercarpal and radiocarpal joints of the horse. Arthroscopic anatomy of the equine intercarpal and radiocarpal joints was documented in six cadaver limbs and on observations made during surgical treatment of horses with carpal osteochondral fractures. Instrument positions and arthroscopic visualisation were recorded. The cadaver limbs were dissected and iatrogenic lesions recorded. A single arthroscopic portal examination was adequate in both joints; however, a second arthroscopic portal improved visualisation. The intercarpal joint was more easily examined than the radiocarpal joint because of anatomical differences. Iatrogenic lesions wer...
Experimental reactivation of equid herpesvirus 1 (EHV 1) following the administration of corticosteroids. Eight ponies were experimentally infected with equid herpesvirus 1 (EHV 1) (subtype 1). All animals showed clinical and serological evidence of infection and virus was isolated from nasal swabs and leucocytes. These ponies were kept in isolation for a further three months during which time complement fixing antibody decreased at least four-fold. Following immunosuppression with dexamethasone and prednisolone subtype 1 virus was recovered from six of the eight animals within 14 days. Five of these six ponies were viraemic and three of them shed virus in nasal secretions; only four displayed sig...
Isolation of equine coital exanthema virus (equine herpesvirus 3) from the nostril of a foal. The virus causing equine coital exanthema (equine herpesvirus 3) was isolated from a lesion on the nostril of a 2-month-old foal. One week after the mare had returned from a stallion station, vesicular lesions developed on her vulva. They were diagnosed clinically as coital exanthema, and 5 days later a lesion developed on the nostril of her foal. This case is an example of horse-to-horse transmission of coital exanthema virus without coitus. A laboratory diagnosis is necessary to differentiate viruses that cause vesicular lesions about the oral and nasal cavities of horses.
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...
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...
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...
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 ...
