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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.
Use of the portable infrared thermometer as a means of measuring limb surface temperature in the horse. Evaluation was made of the portable infrared thermometer to measure limb surface temperature in 3 horses--first standing in a stall and then placed in lateral recumbency under general anesthesia. To determine the effect of pigment, black and white targets were examined with the instrument under various clinical conditions. In each horse, thermal gradient measurements were consistent along the extremities. Mean limb surface temperatures were less than rectal temperature and greater than ambient temperature. Limb surface temperatures measured in lateral recumbency under general anesthesia were u...
A physiological approach to fluid and electrolyte therapy in the horse. In this article a physiological approach to fluid therapy is discussed, commencing with examination of fluid distribution in the normal horse. The functions of individual plasma electrolyte concentrations are considered and practical causes of acid-base disturbances discussed. When fluid administration is necessary, selection of the route for fluid administration as well as the type of fluid are important considerations and these must be adjusted to the needs of the individual case. Balanced polyionic solutions appear to be most suitable for general use because normal saline can produce hypoka...
The metabolism of promazine and acetylpromazine in the horse. Promazine hydrochloride and acetylpromazine maleate were administered intravenously at clinical dose levels to horses. In urine from horses given promazine hydrochloride, the parent drug and four metabolites were detected. The two major metabolites, present as conjugates were identified after hydrolysis by beta-glucuronidase/arylsulfatase as 3-hydroxypromazine and 3-hydroxydesmonomethyl-promazine. Conjugated 3-hydroxypromazine has been previously identified as a major metabolite in the horse. Two minor metabolites isolated in this study were primaizine N-oxide and promazine N-oxide sulfoxide. ...
Influence of season and age on reproductive activity in pony mares on the basis of a slaughterhouse survey. Reproductive tracts were collected monthly over a 3-year period from 1,003 nonpregnant ponies at a slaughtering plant in Wisconsin. Ages of the animals were estimated from tooth replacement and wear. Ovaries were examined for follicular and luteal activity. There were no differences between left and right ovaries in size or occurrence of ovulation. The frequency of multiple ovulations, 10%, was higher than previously reported for ponies. The follicular changes during the ovulatory cycle did not support a two-wave theory of follicular growth. Ovarian activity changed seasonally, a finding simil...
[Some clinical biochemical features of ‘tying up’ in horses (author’s transl)]. The changes in the activities of lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) in de blood of thirty-three horses with 'tying up' were compared. The extent to which the serum enzymes LDH, CPK and glutamic oxaloacetic transaminase (GOT) and the changes in the activities of these enzymes after suitable labour can be used in the diagnosis of 'tying up' and in following the recovery of patients was studied.
Fractionation and partial characterization of alpha-1-protease isoinhibitors of horse. The principal alpha-1-protease inhibitor of horse was fractionated by classical methods and analysed with a modified fibrinogen-agarose gel electrophoretic method of high sensitivity and resolving power. Starting with an electrophoretically homogeneous inhibitor in unfractionated serum, two isoinhibitor bands became apparent after fractionation with (NH4)2SO4 and DEAE-cellulose DE-52 ion-exchange chromatography. The isoinhibitors differed in electrophoretic migration and in the elution pattern from Sephadex G-100 gel filtration, but possessed identical antigenic determinants and enzyme specifi...
Lymphocyte responses to virus and mitogen in ponies during experimental infection with equine herpesvirus 1. Six pony foals, experimentally infected with equine herpesvirus 1 (EHV-1), were studied for their lymphocyte responses to EHV-1 and phytohemagglutinin (PHA) stimulations. Lymphocyte blastic transformation in the presence of EHV-1 appeared as early as 2 days after the foals were inoculated, reached a peak in 7 to 10 days, and subsequently decreased. In contrast, the lymphocyte blastic transformation in the presence of PHA increased sharply, reaching a peak in 2 to 3 days, and then decreased to its lowest level in 10 days after which it returned to its near preinoculation level. As for the mecha...
Recovery of peripheral chemoreceptor function after denervation in ponies. Resting ventilation (PaCO2) and ventilatory responses to acute hypoxia and to intravenous NaCN were assessed over a 4-yr period following cutting of the carotid sinus nerves and stripping the adventitia of the aortic arch. The data indicated essentially complete loss of peripheral chemoreceptor function immediately after surgery and hypoventilation during normoxia (delta PaCO2 = +8.7 Torr). There was a time-dependent, partial recovery of peripheral chemoreceptor function between 2 and 22 mo after surgery. Approximately 10% of the ventilatory response to iv NaCN returned, and 30-40% of the norm...
Dietary fat and exercise conditioning effect on metabolic parameters in the horse. Four isocaloric diets containing 4, 8, 12 and 16% dietary fat (as soybean oil) were fed to four horses at four intervals according to a Latin square design. After 3 weeks of conditioning at each interval, diet effects were evaluated by trotting all horses at 3.2 m/sec for 6 hours. Pre- and posttrotting responses were measured in muscle and liver glycogen, serum long-chain fatty acids, serum electrolytes, serum enzymes, serum cholesterol, plasma glucose, packed cell volume and hemoglobin. Dietary fat was highly correlated with exercise-induced plasma glucose changes and with cholesterol concent...
The effect of joint position on juxta-articular bone marrow pressure. Relation to intra-articular pressure and joint effusion–an experimental study on horses. Six metacarpo-phalangeal joints of adult horses were studied. Pressure measurements were made in the joint and the metacarpal bone with simultaneous measurement of the systemic arterial blood pressure. Investigations performed to study the effect of joint position on juxta-articular bone marrow pressure showed that an increase in joint flexion was always followed by a rise in intraosseous pressure with a significant increase at flexion above 60 degrees. Increase in intra-articular pressure which was achieved by injection of saline was always followed by a slower rise in intraosseous pressure. ...
Sexual behavior, seminal pH and accessory sex gland weights in geldings administered testosterone and(or) estradiol-17 beta. Sixteen stallions were castrated and 30 days later assigned to one of four treatments: (1) testosterone propionate (175 microgram/kg body weight), (2) 17 beta-estradiol-3-benzoate (44 micrograms/kg body weight), (3) a combination of both steroids or, (4) vehicle only. These dosage were administered every other day for 18 days. The dosages were then doubled and continued for 20 days. Concentrations of testosterone and estradiol in serum decreased rapidly after castration and stabilized within about 6 hours. Mean concentrations of testosterone and estradiol maintained by the steroids were 1.4 an...
Equine postanesthetic forelimb lameness: intracompartmental muscle pressure changes and biochemical patterns. Intracompartmental muscle pressures were recorded from the right and left forelimbs (extensor carpi radialis, triceps brachii) of healthy horses maintained in left lateral recumbency while under deep halothane anesthesia for 180 to 240 minutes. Cardiac output, blood pressure, blood gases, and acid-base status were monitored throughout the anesthesia, and electrolyte levels (Ca2+, P+, K+, Cl-, Na+) and enzyme activities (aspartate aminotransferase (AST), creatine phosphokinase (CPK), and blood lactate) were monitored for 7 days. Postanesthetic forelimb lameness was produced in 5 of the 6 horses...
[Effect of 2 methods of demineralization on the on the preservation of glycoproteins and proteoglycans in the intertubular and peritubular dentin in the horse]. The effect of 2 methods of demineralization on the preservation of proteoglycans and glycoproteins was studied in the intertubular and peritubular dentine of the horse. The specimens embedded in Epon were demineralized with a 2% acid formic solution (Bonucci and Gheradi, 1975). Other fragments were treated with an organic solution of EDTA alkylammonium salt (Scott and Kyffin, 1979). These methods preserved in a satisfactory way these labile organic components. In the intertubular dentine, glycoproteins and proteoglycans were also identified, either associated with collagen fibres as a glue and...
Helix packing and subunit conformation in horse spleen apoferritin. An electron density map of horse spleen apoferritin at 0.28-nm (2.8 A) resolution and its preliminary interpretation have been described previously. Rigorous examination of this and newer maps at the same nominal resolution but calculated from more extensive data sets, including model building in a Richards' comparator, now allows us to report on structural features in more detail. We list inter-helical angles within and between neighbouring subunits, and describe a new short region of inter-subunit anti-parallel pleated sheet. A short section of electron density not properly accounted for in ...
[The immunological relation between human and equine Gc proteins (author’s transl)]. The immunological comparison of human and equine Gc proteins showed partial identical reactions between both species. Immunizations of goats and rabbits with horse serum produced antisera able to recognize human Gc proteins.
[The effect of age and training on the ECG time curve of purebred horses]. In 246 horses of the English Thoroughbred breed of several age categories, divided into four test populations, the influence was studied of age and training on the pulse rate and time intervals of ECG (PQ, QRS, QT and QTc). It was found that with the increasing age and training action slowed down gradually. Duration of the atrioventricular path (PQ) is prolonged, time of ventricular activation (QRS) and time of the electrical systole (QT) including its value corrected according to the actual pulse rate (QTC). In this way the origin of the so called sports electrocardiogram in trained race hors...
Comparison of milk and blood plasma progesterone concentrations in cycling and pregnant mares. Progesterone concentrations were measured in milk and blood plasma for 15 mares throughout a normal estrous cycle and early pregnancy to determine the feasibility of utilizing progesterone in milk as an indicator of pregnancy. Samples were obtained daily from foaling until diagnosis of pregnancy by rectal examination at 30 to 35 days of gestation. Progesterone in milk and blood plasma was quantified by radioimmunoassay. Mean progesterone concentrations (+/- SE) in plasma from foaling to foal heat and during estrus, luteal phase and pregnancy were .51 +/- .09 ng/ml, .53 +/- .08 ng/ml, 3.88 +/- ...
