Topic:Adult Horses
Adult horses encompass a category of equines that have reached maturity, typically considered to be around five years of age and older. This stage of life is characterized by full physical development and the potential for peak performance in various activities such as riding, racing, and work. Adult horses require specific nutritional, health, and management practices to maintain optimal condition and performance. The study of adult horses covers a range of topics, including physiology, behavior, and the impact of environmental factors on their well-being. This page compiles peer-reviewed research studies and scholarly articles that explore the physiology, health management, and performance aspects of adult horses.
Cimetidine for treatment of melanomas in three horses. Cimetidine, an H2 histamine antagonist, was used in the clinical management of progressive, multifocal melanomatosis in 3 adult gray horses. Prior to treatment, the tumors had increased rapidly in size and number in 2 horses (duration of 6 and 27 months, respectively) and slowly in the third horse (duration of 48 months). All 3 horses were treated with cimetidine (2.5 mg/kg of body weight, PO, q 8 h) for 2 months to 1 year. During treatment, the number and size of the melanomas decreased substantially (50 to 90%). The progression of the disease was halted in 2 horses and controlled in the thir...
Pharmacokinetic studies of cimetidine hydrochloride in adult horses. Histamine type II (H2) antagonists inhibit gastric acid secretion and are useful in treating gastric and duodenal ulcer disease. To provide some information on the pharmacokinetics of the H2 antagonist cimetidine, adult horses were given 3.3 mg/kg cimetidine intravenously (iv) or 3.3 and 10 mg/kg orally. Plasma cimetidine concentrations after 3.3 mg/kg orally were too low to measure. Following 3.3 mg/kg iv, cimetidine displayed two-compartment characteristics with a t1/2 of 0.083 +/- 0.039 h and t1/2 of 2.23 +/- 0.64 h. The total body clearance was 0.443 +/- 0.160 litre/h/kg and the mean resid...
Effect of body posture on cardiopulmonary function in horses during five hours of constant-dose halothane anesthesia. Cardiovascular and respiratory functions were serially characterized in 7 healthy, spontaneously breathing, adult horses (from which food had been withheld) during 5 hours of constant 1.06% alveolar halothane (end-expired halothane concentration of 1.06%; equivalent to 1.2 times the minimal alveolar anesthetic concentration for horses). To enable comparison of temporal results in relation to 2 body postures, horses were studied in lateral recumbency (LR) and dorsal recumbency (DR) on separate occasions. Temporal changes in results of measures of circulation previously reported from this labora...
Dopamine in the cerebrospinal fluid of prepubertal and adult horses. Catecholamine concentrations (pg/ml) in the cerebrospinal fluid (CSF) of prepubertal (n = 9) and adult (n = 18) horses were determined by radioenzymatic assay. Norepinephrine was low or non detectable in all CSF samples. In contrast, measurable CSF dopamine concentrations were effected by age, reproductive status and exogenous steroid treatments. The concentration of dopamine in the CSF of prepubertal females (733 +/- 92) was greater (p less than 0.05) than the concentration in the CSF of prepubertal males (117 +/- 67). Prepubertal male horses which were treated with testosterone for 5 days (5...
Degree of correspondence between contractile and oxidative capacities in horse muscle fibres: a histochemical study. Samples taken from the middle gluteal muscle of 95 untrained adult horses of different ages and sex were subjected to histochemical analysis using the myosin adenosine triphosphatase (m-ATPase) and nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) staining techniques. Fibres were classified into types I, IIA and IIB according to m-ATPase activity after preincubation at pH 4.4. The percentage of FT (Fast-Twitch Glycolytic) fibres and the proportion of IIB fibres with "high" and "low" oxidative capacity were determined in serial sections stained for NADH-TR. Statistical analysis ...
Heart weight and running ability. The weight of the heart as determined by dissection techniques was compared with liveweight and total muscle weight in different types of horses and dogs as adults and during growth. With increasing body size both within and between species, heart weight forms a lesser proportion of liveweight and of total muscle weight. Heart weight forms a greater proportion of liveweight in Thoroughbreds and Greyhounds (breeds noted for high speed running) than in other less fleet members of their species and Greyhounds have greater heart weights relative to total muscle weight than other dogs.
Effects of halothane and isoflurane on baroreflex sensitivity in horses. Baroreflex sensitivity (BS) was used to quantitatively assess the effects of halothane and isoflurane on the heart rate/arterial pressure relationship during steady-state (10 minutes) and dynamic pressure changes in adult horses. Arterial pressure was decreased in response to nitroglycerin or sodium nitroprusside and increased in response to phenylephrine HCl. Mean (+/- SEM) BS in awake horses was 28.9 +/- 2.6 and 13.2 +/- 2.0 ms/mm of Hg during steady-state decreases and increases in systolic arterial pressure (SAP), respectively. Halothane and isoflurane either significantly (P less than 0.0...
Effects of atracurium administered by continuous intravenous infusion in halothane-anesthetized horses. Atracurium (0.4 mg/ml in isotonic NaCl solution) was administered by IV infusion to 7 healthy adult horses for 2 hours. Over the 2-hour period, a 95 to 99% reduction of train-of-four hoof-twitch response was maintained by 0.17 +/- 0.01 mg of atracurium/kg of body weight/h, for a total of 161 +/- 6 mg of atracurium (mean +/- SEM) for horses 1 to 4, 6, and 7. Horse 5, a mare in estrus, required 0.49 mg of atracurium/kg/h to maintain comparable relaxation. Hoof-twitch recovery time from 10 to 75% of baseline strength was 19.8 +/- 2.5 minutes for all horses. The 10 to 75% recovery time for horse 5...
Microvascular circulation of the ascending colon in horses. Microvascular circulation of the ascending colon in healthy horses was studied using microangiography, light microscopy, and scanning electron microscopy. The pelvic flexure with 30 cm of ventral and dorsal colon attached was removed from 14 adult horses immediately after horses were euthanatized. The lumen was flushed with warm water, and this section of the ascending colon was placed in a 37-C bath of isotonic NaCl. In sections from 8 horses, colic vessels were perfused with a radio-opaque medium for microangiography. After angiographic evaluation, tissue sections were prepared for light mic...
Pharmacokinetic disposition of an immediate-release aminophylline and a sustained-release theophylline formulation in the horse. The pharmacokinetic disposition of theophylline was determined by high-performance liquid chromatographic analysis of plasma samples from six healthy, adult horses following the administration of intravenous aminophylline (dosed at 9.94 mg/kg as theophylline), immediate-release aminophylline tablets (dosed at 9.94 mg/kg as theophylline), and sustained-release theophylline tablets (dosed at 20 mg/kg). The elimination rate constant (lambda z), apparent volume of distribution (Vz), and clearance (Cl) determined by compartmental analysis of the intravenous data were 0.07 +/- 0.01 h-1, 0.80 +/- 0.0...
Phenolsulfonphthalein pharmacokinetics and renal morphologic changes in adult pony mares with gentamicin-induced nephrotoxicosis. Changes in renal function, determined by pharmacokinetics of phenolsulfonphthalein (PSP), and renal morphologic features were examined in adult pony mares given 20 mg of gentamicin sulfate/kg of body weight, IV, q 8 h (group A) n = 7 or isotonic saline solution, IV, q 8 h, n = 5 (group B) for 14 days. Susceptibility of ponies to gentamicin-induced nephrotoxicosis was varied. Two group-A ponies developed acute renal failure and were euthanatized before treatment day 14, whereas 5 group-A A ponies did not develop physical or behavioral abnormalities after 14 days of gentamicin administration. Al...
[The development of the anti-phospholipase A2 antibody response in horses inoculated with venom for the production of polyvalent antisnake serum in Costa Rica]. The development of antibody response against phospholipase A2 activity of Bothrops asper venom was studied in a group of adult and healthy horses used in the production of the polyvalent antivenom at the Instituto Clodomiro Picado. Simultaneously, the general condition of the animals during the immunization schedule was also studied. There was a great individual variability in the immune response, although most of the horses studied reached the highest neutralizing titer after injection of doses of venom of 30 mg and 50 mg. On the other hand, in horses that had been previously immunized and we...
The arterial supply of the navicular bone in adult horses with navicular disease. A macroscopical, arteriographical and histological study was made of the arterial supply of the navicular bones of horses with clinical and/or radiographic signs of navicular disease. Based on the clinical and radiological findings the navicular bones of 40 Warmblood horses are divided into four different groups. In the pattern of the arteriogram obvious changes are noticed: an imbalance and a distal to proximal shift between the distal and proximal arterial supply occur, indicating a reduction of the distal blood supply with a compensatory reaction of the proximal, medial and lateral supply. ...
The arterial supply of the navicular bone in the normal horse. An arteriographic and histological study of the arterial blood supply of 35 navicular bones, from 19 adult horses with no clinical or radiographical signs of navicular disease, is described. The arteries enter the navicular bone from four directions: distal, proximal, medial, and lateral. The navicular bone can be divided into areas which receive arteries from one, two, or three directions, whereas the distal supply covers the largest part of the navicular bone. The distal arteries enter the navicular bone through the nutrient foramen which contains loose connective tissue, nutrient vessels an...
Technique for transrectal ultrasonography of the cranial mesenteric artery of the horse. Transrectal ultrasonography was successfully used to image the cranial mesenteric artery and its branches in 23 adult horses. The artery could be imaged from its origin at the aorta distally to identify several bifurcations. The method for transrectal imaging of the cranial mesenteric artery and its major branches required 3 distinct transducer positions. One position was used to locate the cranial mesenteric artery by imaging the caudal portion of the aorta from the aortic bifurcation cranially to the level of the cranial mesenteric artery. The second position was used to image the origin of ...
Transrectal ultrasonography of the cranial mesenteric artery of the horse. Transrectal ultrasonography was performed on the cranial mesenteric artery and its major branches in 23 conscious adult horses. Ultrasonographically, 25 arterial segments were classified as either normal or abnormal. These ultrasonographic classifications were later compared with the gross and histologic evaluations of each artery following necropsy of each horse. In this study, transrectal ultrasonography as a diagnostic test for verminous arteritis had a 90% sensitivity for detecting normal arteries and an 86% specificity for detecting abnormal arteries, suggesting that ultrasonography may b...
High frequency jet ventilation in horses: an experimental study. High frequency jet ventilation (HFJV) is a recently developed mode of ventilation that delivers small tidal volumes at frequencies greater than 60 cycles per min via an injection catheter to the animal's airway. The construction of a high frequency jet ventilator suitable for use in adult horses is described. The effectiveness of this ventilator in maintaining normal arterial blood-gas tension was evaluated in five healthy adult horses. The horses were anaesthetised with intravenous acetylpromazine, guaifenesin, and thiamylal, positioned in lateral recumbency and baseline measurements were mad...
Radioimmunoassay of inhibin in various mammals. A sensitive radioimmunoassay (RIA) for the determination of inhibin in peripheral plasma and tissue homogenates of different species has been developed using antisera to partially purified bovine follicular fluid (bFF) inhibin and 125I-labelled bFF 32 kDa inhibin. Antisera were produced by immunization of rabbits with partially purified bFF inhibin prepared by immunoaffinity chromatography. Increasing doses of a high titre antiserum could neutralize the suppressing effect of bFF, porcine follicular fluid and rat ovarian homogenate on FSH secretion from rat anterior pituitary cells in culture. ...
Pancarpal arthrodesis for treatment of carpal collapse in the adult horse. A report of two cases. Two mares with multiple carpal bone fractures, malarticulation and degenerative joint disease were successfully treated with unilateral arthrodeses of the antebrachiocarpal, middle carpal, and carpometacarpal joints. Arthrodesis was achieved by removal of articular cartilage, autogenous cancellous bone graft, and double dynamic compression plating. In one horse, wedge ostectomy corrected the severe, acquired angular limb deformity. External coaptation supplemented the internal fixation. Postoperative complications were limited to cast sores that healed with treatment, although protracted in on...
Effect of oral L-carnitine on its concentration in the plasma of yearling Thoroughbred horses. After an oral dose of 10 g of L-carnitine the plasma concentrations of free and total carnitine increased in five yearling thoroughbred horses, reaching a peak two to four hours after administration, but in two horses there was no increase. In the five which responded, the mean (+/- sd) peak increase in total carnitine concentration was 15.1 +/- 6.9 mumol/litre from a predose mean of 18.8 +/- 3.4 mumol/litre, and the mean peak increase in free carnitine concentration was 13.5 +/- 3.1 mumol/litre from a pre-dose mean concentration of 12.5 +/- 2.2 mumol/litre. These changes were similar to those...
Evaluation of the opsonic capacity of core lipopolysaccharide antiserum of equine origin against smooth Escherichia coli 0111:B4, using macrophage chemiluminescence. A study was performed to determine whether equine antiserum to core lipopolysaccharide (LPS) would enhance phagocytosis of smooth gram-negative (GN) organisms by equine macrophages. Five healthy adult horses (group A) were immunized with a bacterin prepared from the J-5 mutant of Escherichia coli 0111:B4 and Salmonella minnesota R595 to produce antibodies to core LPS. Five horses (group B) served as nonimmunized controls and were given physiologic saline solution instead of the rough mutant bacterin. Serum antibody titers to core LPS and to smooth E coli 0111:B4 were determined by indirect ELI...
Evaluation of the effects of intra-articular injection of dimethylsulfoxide on normal equine articular tissues. To evaluate the effects of intra-articular injection of dimethylsulfoxide (DMSO) on normal equine articular structures, 7 adult horses with clinically normal carpi were allotted to 2 treatment groups (group A, n = 4; group B, n = 3). In each horse after collection of synovial fluid samples, the right antebrachial carpal and middle carpal joints were aseptically injected with 2 ml of a 40% solution of 90% medical grade DMSO in lactated Ringer solution, and the corresponding joints of the left forelimb (controls) were injected with 2 ml of lactated Ringer solution. In group-A horses, 2 ml of syn...
Evaluation of the tibia as a source of autogenous cancellous bone in the horse. A 1 cm defect was created in the proximal medial cortex of 12 tibiae, cancellous bone was removed from the site, and the bones were fractured by loading in torsion. The fractures did not occur through the donor sites and the fracture patterns and loads to fracture were similar for the treated tibiae and their untreated mates. Cancellous bone was harvested from the proximal medial aspect of both tibiae in nine adult horses. The soft tissue wounds were monitored for more than 10 days in seven horses and healing of the osseous defects was evaluated radiographically at regular intervals to month 6...
Transfer of deep circumflex iliac flaps to the tarsus by microvascular anastomosis in the horse. Eighteen deep circumflex iliac flaps were elevated in healthy adult horses. Four flaps survived well when elevated as islands, but five orthotopic flaps and nine heterotopic flaps transferred to the tarsus and face failed. Technical reasons could explain the failure of the orthotopic flaps, but not the heterotopic flaps. Failure of the heterotopic flaps was apparently caused by the no-reflow phenomenon.
Regional gastric pH measurement in horses and foals. The pH of the gastric mucosal surface and gastric content was measured in 18 foals (mean age: 20 days) and 27 horses (mean age: 2.9 years) with a pH electrode passed through an endoscope biopsy channel. A reference electrode was attached to a shaved area on the neck. pH Measurements of the gastric mucosal surface at the dorsal squamous fundus (SF), squamous mucosa adjacent to the margo plicatus (MP), glandular fundus (GF) and the fluid or feed contents of the stomach were recorded in duplicate for each animal. In adult horses, the SF pH was greatest (5.46 +/- 1.82), with a decreasing pH ventra...
Effects of diet and feeding on postprandial serum gastrin and insulin concentration in adult horses. Gastrin is the only hormone known to stimulate secretion of hydrochloric acid. It also has trophic effects on specific parts of the mucosa of the gastrointestinal tract. Using radioimmunoassay techniques, postprandial serum gastrin and insulin concentrations were measured in six adult horses to establish effects of different diets on gastrin concentrations. Insulin concentrations were measured to provide support to the patterns of gastrin secretion because patterns of insulin secretion were already known. The horses were fed coastal bermuda hay, or twice daily 5 kg of a complete pelleted ratio...
Vascular anatomy of the equine small colon. The vasculature of 22 small colons from dead adult ponies was perfused with latex or barium sulphate solution. The vascular anatomy was studied by use of dissection and alkali digestion of the latex specimens and microangiography of the barium sulphate-perfused specimens. The small colon is supplied by the caudal mesenteric artery. The left colic artery arises from the caudal mesenteric artery, which then becomes the cranial rectal artery. Branches from the left colic and cranial rectal arteries form anastomosing arcades that become narrower distally along the length of the small colon. From t...
Surgical management of duodenal obstruction in an adult horse. A 3-year-old Standardbred stallion was admitted for treatment of acute enterocolitis. The horse improved in response to empiric treatment, but subsequently developed ventral edema, scrotal abscessation, and severe laminitis. Improvement again was seen, but on day 29 of hospitalization, the horse developed rapid heart rate and signs of abdominal pain. Exploratory celiotomy revealed complete obstruction of the descending portion of the duodenum, 20 cm caudal to the duodenal sigmoidal flexure. Three-tier duodenojejunostomy and jejunojejunostomy were performed to bypass the duodenal obstruction.
Comparative ventilation and gas exchange in the horse and the cow. Ventilation and gas exchange were studied in healthy, adult horses and cows, two large species with different lung structures and different breathing patterns. The oxygen uptake (VO2), carbon dioxide output (VCO2), respiratory rate (fR), minute ventilation (VE), alveolar ventilation (VA), alveolar oxygen pressure (PAO2), and VE/VO2 ratio were higher in the cows, while the tidal volume (VT) and physiological dead space (VD) were larger in the horses. The arterial blood gases, alveolar-arterial oxygen pressure difference (PAO2-PaO2) and VD/VT ratio did not differ between the two species. The hig...
Pneumonia, lung abscesses and pleuritis in adult horses: a review of 51 cases. Case records are reviewed of 51 adult horses in which a diagnosis of pneumonia, pulmonary abscess or pleuritis had been made. Forty-five horses were afflicted with pneumonia and/or pulmonary abscesses; in 11 of these the infection was primary, whereas in 34 it was secondary to another disease process (inhalation of food or saliva, thoracic trauma, generalised infection, airway disease, neoplasia or thromboembolism). Of the 11 horses with primary pulmonary infections, 10 appeared to be associated with a previous episode of stress; this took the form of long distance travel in eight cases. There...