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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.
Motor events in equine large colon. The equine large colon is the major cellulose-fermentation locus of these species. The area of juncture of the ventral and dorsal divisions of the equine large colon was characterized, in 13 chronic unanesthetized animals and in 25 in vitro preparations, as an area of resistance to aboral flow. This is a probable pacemaker area. The reservoir function of this part of the colon is apparently facilitated by the presence of a pacemaker at this level. There was a general rise in recorded intraluminal pressure peaks during the first hour of feeding. This characteristic was not altered after resecti...
Plasma and synovial fluid lysozyme activity in horses with experimental cartilage defects. Cartilaginous defects were created in the radiocarpal joints of 12 horses. Synovial fluid cytologic features, lysozyme activity, and beta-glucuronidase activity were monitored for 16 days. A comparison was made of plasma lysozyme and beta-glucuronidase activity and of synovial fluid lysozyme, beta-glucuronidase, and leukocyte concentrations. Plasma lysozyme was found to be independent of synovial fluid lysozyme activity. Synovial fluid lysozyme was significantly increased (P less than 0.001) in all joints with surgically induced defects (group I) compared with controls (arthrocentesis done; gr...
A study of Klebsiella pneumoniae infection in the uterus of the mare. Two experiments incorporating 13 mares were conducted for the purpose of producing and monitoring intrauterine infection with Klebsiella pneumoniae. In the pilot study, the infection was produced with strains of K pneumoniae type 68 and type 10 isolated from the genital tract of stallions with a history of breeding problems. In the principal study, K pneumoniae type 68 was used to produce the infection. Tampons and guarded culture swabs were used to obtain uterine samples in the pilot study. In comparing the efficacies of isolation of K pneumoniae with the tampons and isolation with standard g...
Differences in the interactions of liver alcohol dehydrogenases with probes binding into the substrate pocket. The interactions of three groups of probes (berberine alkaloids, tricyclic psychopharmaca and acridine derivatives) with isoenzymes of horse liver alcohol dehydrogenase and with rat liver alcohol dehydrogenase have been examined. These compounds inhibit the activity of the EE isoenzyme of horse liver alcohol dehydrogenase but differ in their behaviour towards the steroid-active enzymes (i.e. the ES isoenzyme of horse liver alcohol dehydrognase and alcohol dehydrogenase from rat liver): psychopharmaca inhibit, acridines activate and berberines do not bind. The ligands differ also in their influ...
Evaluation of uterine tube function in pony mares. Two experimental procedures were investigated in order to assess their usefulness in diagnosing occlusion of the equine uterine tube. The starch grain test, which involves the injection of a starch suspension onto the ovary and the subsequent recovery of starch from the cervix, proved to be safe and reliable. Each tube could be investigated separately. It was found that when starch was injected onto the ovulating ovary on the day of ovulation, there was a delay of four to seven days before starch was recovered from the cervix. The phenolsulphonphthalein (PSP) test, which involves the depositio...
Physiologic effects of succinylcholine chloride in mechanically ventilated horses anesthetized with halothane in oxygen. Succinylcholine chloride, administered to horses anesthetized with halothane in oxygen and mechanically ventilated, caused slight but significant (P less than 0.01) increases in heart rate. Significant alteration in mean arterial blood pressure did not occur, and there were clinically insignificant increases in serum K+ and C1- concentration. Cardiac dysrhythmia and myoglobinuria did not occur. Thus, effects of halothane anesthesia and mechanical ventilation prevented cardiac dysrhythmia and hypertension and greatly reduced the tachycardia generally associated with siccinylcholine administrati...
A technique for the conduct of nutritional balance experiments in horses. Standardbred geldings were used in a number of nutritional balance experiments. These consisted of 28-day cycles each of an 18-day equilibration period in yards and a 10-day settling and collection period in metabolism crates. The crates were made of galvanised metal tubing over wooden flooring covered by rubber matting and rubber sheets. Total faeces were collected in trays at the rear of crates and total urine by canvas funnels slung beneath the sheath of each horse.
Tissue and plasma activity of lactic dehydrogenase and creatine kinase in the horse. Lactic dehydrogenase, although widely distributed in most tissues, was more highly concentrated in skeletal muscle, cardiac muscle, kidney and liver. Isoenzyme patterns showed a selective concentration of LDH5 in skeletal muscle while in the heart LDH 1 and 2 were predominant. In contrast, creatine kinase was only present in substantial concentration in skeletal and cardiac muscle. The serum concentrationof both enzymes showed a wide range of activity.
A re-evaluation of the D (+) xylose absorption test in the horse. The absorption of d-xylose forms the basis of a useful screening test in the investigation of small intestinal disorders in the horse. A comparison has been made of different assay methods and there was no significant difference between the results obtained with the parabromoaniline (PBA) method or the ferric chloride-orcinol (FCO) method. The orthotoluidine method was unsatisfactory. The anticoagulant agent did not affect the test. A dose of 0.5 g commercial grade xylose/kg body weight as a 10 per cent solution given by stomach tube, produced a peak plasma xylose level after 90 min and should...
Evaluation of equine radial and median nerve conduction velocities. Eleven ponies and 13 horses were used to develop a technique for determining conduction velocity for the radial and median nerves and establishing normal limits for these values. One pony was euthanatized to determine the course of the radial and the median nerves. From this dissection, both proximal and distal stimulation sites for the radial and the median nerves were selected, as well as areas for recording muscle evoked responses from the abductor digiti I longus (extensor carpi obliquus) and the radial head of the deep digital flexor muscles. The other ten ponies and the horses were used ...
Evaluation of functional thymic hormones in Arabian horses with severe combined immunodeficiency. Arabian horses with severe combined immunodeficiency disease (SCID) were evaluated for thymic hormone activities using thymic extracts and sera. Extracts prepared from thymus of SCID horses were able to increase the number of spleen cells responding to sheep red blood cells in irradiated, bone marrow-reconstituted mice. In addition, ultrafiltrates prepared from sera of these immunodeficient horses, which contained material with molecular weight of less than 50,000 Daltons could (a) induce a population of human bone marrow precursor cells to differentiate into cells bearing SRBC receptors and f...
Assessment of myocardial function in the horse. 1. Theoretical and technical considerations. The paper discusses the various parameters which are currently used in attempts to assess the contractile efficiency of the myocardium in various species. These procedures depend upon accurate recording of intracavity pressure. The response of a catheter-mounted microtransducer compared with a fluid-filled catheter manometer system is illustrated to show the advantage of the former in providing a true representation of pressure changes.
Hemodynamic and respiratory effects of xylazine-morphine sulfate in horses. The cardiopulmonary effects of two xylazine-morphine sulfate drug combinations (mixtures) given IV were evaluated in horses. In horses given xylazine (0.66 mg/kg of body weight) and morphine sulfate (0.12 mg/kv) IV (experiment 1), there were significant (P less than 0.05) decreases in heart rate, cardiac output, and respiratory rate. Central venous pressure was significantly (P less than 0.05) increased. Arterial and pulmonary arterial blood pressures increased significantly (P less than 0.05) but transiently. Arterial blood gas tensions (PaCO2 and PaO2) and pH remained unchanged. In the horse...
Oxidation of (horse) hemoglobin by copper: an intermediate detected by electron spin resonance. The oxidation of horse hemoglobin by Cu(II) has been followed by the changes in the electron spin resonance spectra of copper. By stopped-flow and freeze-quenching techniques, it is shown that the second-order rate constant for the binding of Cu(II) to hemoglobin is greater than 5 X 10(5) mol-1 s-1 and the apparent first-order rate for the reduction of Cu(II) to Cu(I) is 0.051 s-1. It is also shown that the binding of Cu(II) to hemoglobin is followed by an alteration of the Cu(II) spectrum, decreasing the g values. This process has an apparent rate constant of 17 s-1 and presumably involves a ...
Effects of restrictive suckling on postpartum reproductive performance in mares. Quarter Horse mares (n = 30) and their foals were used in a 2-year study. Objectives of the study were (i) to determine the effects of a treatment regimen, which permitted nursing for four 1-hour periods each day, on the postpartum reproductive performance of the dams, and (ii) to assess the effects of this procedure on the growth and development of foals. Mares in the restricted suckling treatment group showed estrus and ovulated sooner (P less than 0.01) after parturition than did control mares during the first year of the study, but not during the second year. Plasma progesterone concentrat...
