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Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
Infertility in the horse associated with chromosomal abnormalities. Reproductive failure was studied in 12 phenotypically normal mares (9 Arabian, 3 Quarter horses, 1 Appaloosa and 1 pony). Karyotyping was performed using lymphocytes isolated from peripheral blood by density gradient procedures, followed by standard culture methods for karyotyping. Nine mares had karyotypes of 63,XO; 1 had 63,XO/64,XX; 1 had 63,XO/64,XY and 1 had 64,XY. All mares had small, firm ovaries that when removed and examined from 4 mares, lacked germ cells and consisted of undifferentiated ovarian stroma.
Physical optics of the equine eye. The equine eye was treated as a general lens system and calculations were done to determine image position in relation to the retina for objects at a distance of infinity, 100 m, and 1 m. The retina is 19.1 mm behind the posterior surface of the lens; therefore, the image appears 14.6 mm posterior to the retina at infinity and at 100 m, and 16.3 mm at 1-m distance on a horizontal axis. The animals studied were hyperopic. It is evident that the horse must move its head or eye, or both, for optimal visual acuity. At the same time, some objects in the total field of vision are imperceptible or in...
Cardiac output, left ventricular ejection rate, plasma volume, and heart rate changes in equine laminitis-hypertension. Acute laminitis-hypertension was produced experimentally by carbohydrate overloading of the gastrointestinal tract in 8 horses, and the resulting hemodynamic changes were measured. Statistically significant (P less than 0.01) increases in cardiac output, left ventricular ejection rate, heart rate, and arterial pressure were related to statistically nonsignificant changes in peripheral resistance and a delayed (Obel grade 3 plus 24 hours) decrease in plasma volume. When compared with control values, the doubling of cardiac output and left ventricular ejection rate simultaneous with little or no...
Laboratory methods of equine pregnancy diagnosis. Rectal examination is a reliable method of diagnosing pregnancy in the mare. Also, test kits are available for the simple quick detection of pregnant mare serum gonadotrophin. Nevertheless there is a considerable demand by practitioners for an independent laboratory service in equine pregnancy diagnosis, particularly during the gestational phase when placental gonadotrophin is concentrated in the blood. An initial attempt to provide a service by means of the agar gel diffusion test was disappointing and alternatives were sought. The primary requirements for an ideal alternative technique were ...
Equine angiotensin converting enzyme: a zinc metalloenzyme. 1. Angiotensin I converting enzyme from horse plasma has been extensively purified and shown to be homogeneous by disc-gel electrophoresis. 2. The metal ion involved in the catalytic reaction of the enzyme has been identified for the first time as zinc by atomic absorption spectrometry. 3. A number of other physicochemical properties of the enzyme are described and compared with results obtained by other investigators. The molecular weight was determined by gel filtration to be 113 000 daltons. The pH maximum was found to be 7-4. The chloride activation of the enzyme appears to act by facilita...
New techniques to measure blood cholinesterase activity in domesticated animals. A macromethod and a semimicromethod were developed to measure erythrocyte acetylcholinesterase activity in cattle, sheep, goats, horses, dogs, and swine, and to measure plasma cholinesterase activity in horses, dogs, and swine. Comparison of the 2 methods with erythrocytes of sheep, cattle, goats, and horses indicated both methods gave similar results. They can be done in a shorter time and are more sensitive than Michel's method. Normal deltapH values per minutes, with standard deviations for blood cholinesterase activity of animals of different ages, sexes, breeds, and species, were: 0.76 +/...
Training and exercise change respiratory properties of blood in race horses. Effects of training and exercise on blood respiratory properties were investigated in standard-bred race horses. Training caused an increase in the circulating O2 capacity at rest from 18.4 to 21.0 vol%, and in the O2 capacity during exercise from 24.9 to 30.3 vol%. An increase in the in vitro oxygen affinity [P50(PH 7.4, 37.9 degrees C)] of about 2 mm Hg correlated with a decrease in the red cell concentration of 2,3-diphosphoglycerate (DPG) from 6.35 mM-1-1(E), erythrocytes. Trained horses also showed an acute lowering of the red cell DPG concentration after maximal exercise. The physiologic...
Flow rates from an intermittent positive pressure breathing-anesthetic delivery apparatus for horses. Inspiratory flow rates were measured and compared in an equine intermittent positive pressure breathing-anesthesia delivery apparatus powered by a positive phase ventilator, a positive-negative phase ventilator, and a modified positive phase ventilator with automatic flow acceleration at driving pressures of 2,600, 4,400, and 5,200 mm of Hg (50, 85, and 100 psi). The last-named apparatus consistently produced the highest flows for a given ventilator setting and driving pressure. Regardless of the unit used, the greater driving pressures and high ventilator range settings produced the greatest ...
Biochemical and physiological effects of catecholamine administration in the horse. Adrenaline was given intramuscularly to resting horses. It increased heart rate, sweating, blood levels of lactic dehydrogenase, aldolase, creatine kinase, glucose, lactate, free fatty acids and glycerol. Responses to isoprenaline, to noradenaline and to adrenaline after pretreatment with propranolol indicated that beta receptors were involved in stimulation of tachycardia, sweating, lipolysis and muscle glycogenolysis, and alpha receptors in stimulation of liver glycogenolysis and leakage of intracellular enzymes. The time course and relative magnitude of the effects on different enzymes was ...
Induction of ovulation and multiple ovulations in seasonally anovulatory and ovulatory mares with an equine pituitary extract. A crude equine pituitary ethanol extract (EE) was used to induce single and miltiple ovulations in seasonally anovulatory pony mares 3-15 years of age. 12 mares were injected daily for 14 days with EE; 6 of the EE-treated mares were also treated with human chorionic gonadotropin (HCG), and 6 control mares received saline vehicle only. In a 2nd experiment designed to determine if EE treatment could induce multiple ovulations in seasonally ovulatory mares, 7 mares were treated during diestrus, 7 mares were treated beginning on Day 1 of estrus, and 7 remained untreated. The results of experiment ...
Scanning electron microscopy of equine synovial membrane. The scanning electron microscopy of synovial membrane from the radiocarpal and intercarpal joints near the lateral and medial borders of the tendon of the extensor carpi radialis muscle was studied in 5 ponies. Three different morphologic types of synovial membrane were observed. Type 1 synovial membrane was folded and had a surface mat of fibers separated by 1- to 5-micron-diameter holes. The 2nd and 3rd types of synovial membrane were both villous. The surface of type 2 synovial membrane was fibrillar but the surface of type 3 synovial membrane was cellular. The type of synovial membrane pre...
Anoestrous conditions in the mare, their diagnosis and treatment. The condition of anoestrus in the mare is described and the various causes of this syndrome are discussed. A regimen for examining systematically the clinically anoestrus mare is proposed, and methods of treatment are suggested.
Echocardiography in the horse. Echocardiograms were obtained from 25 standing, clinically normal horses, using an ultrasonic recording device. The echobeam penetrated the right thoracic wall in the area of the 4th to 5th intercostal space, with a frequency of 2.5 mHz. Measurements of left ventricular wall thickness generated a mean value of 3.2 +/- 0.18 (SEM)cm, whereas the left ventricular chamber diameter in diastole was 9.3 +/- 0.30 cm and in systole was 5.7 +/- 0.23 cm. The aortic root dimensions had a mean of 7.7 cm, with a SEM of 0.16. Mitral valve closing slope (E-F) was calculated to be 17.7 +/- 0.87 mm/second, and ...
Tissue distribution and blood levels of gamma-glutamyl transferase in the horse. In the horse, gamma-glutamyl transferase (GGT) was found to be mainly located in the kidneys, liver and pancreas. As renal lesions are followed by a urinary escape of enzyme, it can be assumed that if there are raised serum enzyme levels then the source will be chiefly from the liver and pancreas. In the blood, GGT can be measured either in plasma or serum. Its mean level in 58 horses was 12 U/L. This level was not affected by moderate dilution or slight haemolysis and its activity was only slightly decreased by storage at--30 degrees C. The relative hepatic specificity of this enzyme and its ...
Studies on the synovia in healthy horses with particular reference to the protein composition. Synovial fluid and blood were collected from 18 clinically healthy brood mares in resting conidition. The following parameters were analysed: total leucocytes, glucose, alkaline phosphatase (AP), lactate dehydrogenase (LDH), total protein, albumin, total globulin, albumin/globulin ratio and electrophoretic protein picture. The serum/synovia ratios were calculated for all parameters. It was considered to be of greater diagnostic value to compare these serum/synovia ratios rather than to look at the individual concentrations in synovia. The results obtained did not materially differ from those i...
Some haematological and biochemical parameters in race horses in Hong Kong. Haematological and biochemical values were determined in 2 groups of flat-race horses, which were trained on the same track in Hong Kong. The first group comprised 217 horses (435 blood samples) from various training strings. The second group, 66 horses (309 blood samples) were from one string kept under similar managemental conditions, but given salts by stomach tube 8 hours before blood sampling. Both groups were sub-divided to show the efs, thus confirming work by other authors. The lower haematological values in the group of horses given salts were discussed and the effect of water retenti...
A method for indirect measurement of arterial blood pressure in the horse. A method using the Doppler ultrasound principle for indirect determination of arterial blood pressure in the horse is described. The method is simple and suitable for field situations. Validation studies show that systolic and diastolic blood pressure measurements bear a close relationship to true values obtained by direct measurement.
Horses lung: Report of two cases. Two cases of horseshoe lung are described; one was suspected and the other was diagnosed preoperatively. Both underwent successful surgical treatment. The embryology of this anomaly is briefly reviewed with reference to the closely related scimitar syndrome (anomalous venous return of right lung to inferior atriocaval junction). Diagnostic studies are discussed with stress on the need for a thorough functional evaluation of both the heart and lungs before the surgical indication is made.
