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.
Fujita K, Suzuki I, Ochiai J, Shinpo K, Inoue S, Saito H.We found that aloe extract contains a lectin-like substance which reacts with serum proteins of various animals. Furthermore, in human serum 2 proteins, alpha2-macroglobulin and alpha1-antitrypsin, were shown to be reactive with aloe extract.
David JS, McCullagh KG.A large anastomosis of the spermatic artery and vein is described. This was found while surgically removing an abdominal testis. Before surgery the animal wanted to rear after exercise and could not stand on 3 legs for any length of time while being shod. This unusual behaviour disappeared after removal of the mass. The performance and conformation of the horse has also greatly improved.
Vanselow B, McCarthy M, Gay CC.The occurrence and timing of heart sounds were examined from phonocardiograms taken from the mitral, aortic and tricupsid recording areas in each of 18 horses. 10 sound events could be identified with each cardiac cycle. Atrial contraction produced up to 3 sound events. The first heart sound consisted of 4 components whereas the second sound was single. Two sound events were associated with the 3rd heart sound in early diastole. The occurrence of third and fourth heart sound components varied between horses and between recording areas. The mitral recording area was considered most satisfactory...
Odberg FO.The ability of 10 horses to hear frequencies between 14 and 25 Kc/s was tested. The horses appeared to perceive ultrasounds by showing either fright reactions or Pryer reflexes to all of the 12 frequencies. The highest frequencies were heard less by older animals, and elicited more reactions in geldings than in mares.
Chand N, Eyre P.Histamine, 2-methylhistamine (a specific H1-agonist), 5-HT, PGF2alpha, SRS-A, bradykinin (BK) and carbachol contract bronchial and tracheal smooth muscles of the horse. Isoprenaline, PGE1, E2, dimaprit and 4-methylhistamine (last two = specific H2-agonists) relaxed airways which were partially contracted to carbachol. Mepyramine (a specific H1-antagonist) selectively antagonized contractions to histamine. In the presence of mepyramine, histamine caused relaxation of airways partially contracted to carbachol. Metiamide and burimamide (specific H2-antagonists) specifically antagonized or reverse...
Steffey EP, Howland D.Cardiovascular effects of venous alveolar concentrations of halothane in oxygen were studied in 8 young, healthy horses under conditions of constant arterial carbon dioxide tension. The alveolar concentration of halothane was expressed as a multiple of the minimal alveolar concentration (MAC) which was known for each animal. Increasing alveolar halothane concentrations to MAC 2.0 resulted in a progressive and significant (P less than 0.05) decline in systemic arterial pressure and left ventricular work. Cardiac output decreased between MAC 1.0 and MAC 2.0 as a result of a significant (P less t...
Komárek J, Matousek V, Jadrný L.Blood parameters were studied in two groups of horses in the "Velká Pardubická" steeple-chase in 1974, 1975 and 1976. After the race, the levels of lactate showed a manifold increase; an increase was also ascertained in the levels of glucose, sodium, potassium, haemoglobin, in the haematocrit value and in the number of erythrocytes. The following parameters significantly dropped: the levels of acid-base balance - pH, base excess, bicarbonate levels. It was proved that the values of the same parameters in horses during training were incomparably lower. It is advisable to examine horses thorou...
McGuire TC, Crawford TB.Equine fibroblasts persistently infected with equine infectious anemia virus acquire a new cell membrane antigen demonstrable by indirect radioimmunoassay, using infected horse serum as an antibody source.
Kingsbury HB, Quddus MA, Rooney JR, Geary JE.The distal portion of the forelimb of the horse is provided with a stay apparatus composed of tendons, ligaments, and fascia. This stay apparatus provides the major resistance to joint flexion during the support phase of the stride. The laboratory test system described was shown to be able to reproduce in vitro limb motions and hoof forces measured with a running horse. These results indicated the stay apparatus operates in a largely passive mode, active muscle contraction apparently serving to provide rigidity only early in the support phase of the stride. The testing system described was des...
Magnuson NS, McGuire TC, Banks KL, Perryman LE.The in vitro and in vivo effects of corticosteroids on peripheral blood lymphocytes (PBL) from ponies were studied. Prednisolone inhibited lymphocyte stimulation by phytohemagglutin (PHA) in a dose-dependent manner, without inducing lysis even at large doses. The PBL from horses heterozygous for the combined immunodeficiency trait responded to corticosteroid treatment the same as did PBL from normal ponies. Removal of the corticosteroid after incubation with PBL from normal ponies partially restored responsiveness of these cells to PHA. Chronic in vivo treatment of ponies with corticosteroids ...
Wentink GH.The movements of the right hind limb of horses with normal locomotion were studied using cinephotography and electromyography. A model of the cycle of a stride in the walk and the trot was constructed and the kinetic parameters of the segments of the limb were calculated. A good correlation was obtained between the kinetics and the periods of the cycle of a stride during which individual muscles display activity. The results of this study demonstrate that: at placing and lifting, i.e., when a change occurs in the direction of the movement of the limb; b) At the walk, the greatest forces operan...
Stickle RL, Fessler JF.Equine cryptorchidism was examined by a review of the literature and a retrospective study of 350 horses over a 14-year period. The incidence of left vs right testis retention was nearly equal. On the left side, 75.2% of the retained testes were retained abdominally and 24.8% inguinally; on the right side, 41.8% of the retained testes were retained abdominally and 58.2% inguinally. Preoperative diagnosis by rectal palpation of the vaginal rings was considered a valuable technique, with 87.9% accuracy in 190 horses. Invasive and nonivasive surgical techniques for abdominal cryptorchidectomy and...
Forster HV, Bisgard GE, Dempsey JA, Orr JA.Numerous studies have demonstrated the existence of an intracranial [H+] chemoreceptor mechanism capable of stimulating ventilation. 1 Supposedly, this chemoreceptor is located 0.2 mm below the surface of the ventrolateral side of the medulla and is responsive to [H+] in the surrounding cerebral extracellular fluid (ECF). During chronic conditions, ECF [H+] is supposedly in equilibrium with CSF [H+]; hence, stimulus level can be established through sampling and analysis of CSF. In this presentation, we summarize data from studies on spontaneously breathing, unanesthetized ponies which suggests...
Gentry PA, Woodbury FR, Black WD.The clotting times obtained with different assay procedures for routine coagulation tests were examined for horse and pony samples. The whole blood clotting time test and the activated coagulation test seemed to give similar results when both tests were done at 22 C. The results obtained for the activated partial thromboplastin time assay varied, depending on the commercial reagent used for the test. Consistent results were obtained for the one-stage prothrombin time assay with each reagent used.
McClure JJ, Muscoplat CC, Johnson DW, Senogles DR.A miniaturized method for the mixed lymphocyte culture test in the horse is described. The test is performed in either round- or flat-bottom microtitration tissue culture plates. Concentrations of responsing and stimulating cells are varied, depening on the experiment. Significant discrimination between isogeneic and allogenic mixtures is possible after 120 hours' culture when cells are labeled ([3H]thymidine) for the last 16 to 18 hours of the test.
Lawrence LM, Williams J, Soderholm LV, Roberts AM, Hintz HF.Four mature Standardbred horses were used in a 2-period cross-over design experiment to evaluate the effect of feeding state (fed or fasted) on metabolic response to 2 repeated bouts of exercise. Horses were either fasted 15 to 16 h before exercise or fasted for 12 h and then fed 2 kg of whole corn 2.5 to 3 h before exercise. In the first period, 2 horses in each feeding state were exercised. In the second period, the treatments were switched. The exercise test consisted of 2 exercise bouts separated by a 90 min recovery period. Each exercise bout included a warm-up phase and a high intensity ...
Sembrat RF, Di Stazio J, Stremple JF.This study was conducted to determine the feasibility of using alert, conscious ponies as a model for septic shock in man. Ten ponies were given 0.7-5 X 10(9) organisms/kg of body weight of live E coli intravenously over one hour. All ponies died and exhibited signs of low cardiac output septic shock. significant decreases were found in cardiac index to 3.15 +/- 0.1 liters/min/m2 (P less than 0.05), white blood cell count to 1,930 +/- 100 cells/m3 (P less than 0.05), preterminal blood glucose to 75 +/- 5 mg/dl (P less than 0.05), PaO2 to 75.7 +/- 5.7 mm Hg (P less than 0.05), and pH to 7.15 +/...
Marshall JF, Bhatnagar AS, Bowman SG, Morris NN, Skorich DA, Redding CD, Blikslager AT.Flunixin meglumine is used for treatment of equine colic despite evidence of inhibited recovery of mucosal barrier function following small intestinal ischaemic injury. This study aimed to characterise an alternative treatment (AHI-805) for abdominal pain in the horse. Objective: To determine the effect of AHI-805, an aza-thia-benzoazulene derivative, on the cyclooxygenase enzymes and the recovery of mucosal barrier function following ischaemic injury. Methods: Effect of AHI-805 on in vitro COX-1 and COX-2 activity was determined by measuring coagulation-induced thromboxane B(2) (TXB(2)) and l...
Sasaki N, Yoshihara T.Seven Thoroughbred horses were laparotomized and Force Transducers were fixed on the proximal jejunal and cecal serosa. After observation of the digestive tract motility in consciousness, cisapride (0, 0.5, 0.75 or 1 mg/kg) was orally administered. In horses treated with 0.75 mg/kg or 1.0 mg/kg cisapride, the migrating contraction (MC) of the jejunum was significantly increased in frequency.
Baker CB, Newton DI, Mather EC, Oxender WD.The length of diestrus was not changed in 4 mares by taking endometrial biopsy specimens during estrus. In contrast, taking endometrial biopsy specimens on postovulation day 4 induced premature luteolysis and significantly (P less than 0.05) reduced the length of diestrus. A concurrent decrease in serum progesterone occurred to verify the premature luteolysis in these mares. Bacterial cultures of endometrial swab samples from these mares were negative for growth at the first estrus before and after the last biopsy procedures, indicating that luteolysis was induced by the biopsy procedure and w...
Komosa M, Flisińska-Bojanowska A, Gill J.1. In six foals and their mothers (of Standard breed) diurnal changes in the haemoglobin level, red blood cell number and mean corpuscular haemoglobin during the first 13 weeks of foal life were studied. 2. Studies begun when a foal reached 7 days of age and were repeated every two weeks till 13 weeks of foal life. Blood was taken every 6 hr in foals and every 4 hr in mares. 3. No diurnal rhythmicity in parameters studied either in foals or in mares was found. 4. Decrease of haemoglobin level in lactating mares (14.0-12.5 g/100 ml) without changes in red blood cell number were observed. Mean c...
Ghoshal NG.The occurrence of aberrant lymph nodes, on both sides of the head of a horse, belonging to the retropharyngeal lymphocenter has been reported.
Clayton HM, Duncan JL, Dargie JD.The mechanisms involved in the pathophysiological disturbances associated with the presence of mature Parascaris equorum in the small intestine were investigated with radioisotopic techniques. The results suggested that, compared with worm-free controls, infected foals had a reduction in gut motility, an increase in the body solids ratio, a lowering of the body pool of albumin and a decreased ability to incorporate dietary methionine into plasma protein.
Mayaki AM, Abdul Razak IS, Noraniza MA, Mazlina M, Rasedee A.Neurological disorders (NDs) are often fatal to horses. Thus, symptoms of equine NDs commonly indicate euthanasia. Current diagnostic approaches for equine NDs is based on clinical signs, differential diagnoses, analysis of cerebrospinal fluid (CSF), assessment of histopathological lesions, and imaging. However, advances in biofluid biomarkers in the diagnosis of human neurological diseases can potentially be applied to equine NDs. In this review, we described the established human blood and CSF neurobiomarkers that could potentially be used to diagnose equine NDs.
Houle JJ, Hoffmann EM.A passive hemolysis assay system was developed which permitted comparisons of the hemolytic activities of complement (C) from six species. This system employs a single antigen and an antiserum raised in one species. Thus, variations resulting from different target antigens and those inherent in using antibodies (of different affinities and isotypes) raised in a variety of species were minimized. Of the erythrocytes (E) examined, those from horses and guinea pigs were most susceptible to lysis, and either would be suitable, as a tentative choice, for measuring C activity of a previously unstudi...
Kokkonen UM, Hyyppä S, Pösö AR.Plasma atrial natriuretic peptide (ANP) responses were studied in horses during and after a competition exercise test (CET) designed to simulate the endurance test of a 3-day event and including test Phases A-D. CET was repeated 5 times at 2 week intervals at mean temperature +28 degrees C and relative humidity (RH) 58%. Heart rate (HR) was monitored during CET. After CET, the horses were rehydrated with isotonic glucose-electrolyte solution or water. ANP, NH2-terminal pro-atrial natriuretic peptide (NT-ANP), aldosterone, arginine vasopressin (AVP) and plasma proteins (PP) were measured during...
Robertson SA.Three different anaesthetic techniques were studied in normal, healthy Thoroughbred or Thoroughbred type horses. These were (a) acepromazine, thiopentone and suxamethonium; (b) acepromazine, glyceryl guaiacolate and a 'half-dose' of thiopentone; and (c) xylazine and ketamine. Anaesthesia was maintained with halothane vaporized in oxygen and nitrous oxide. All horses underwent either laryngeal or body surface surgery. Heart rate, packed cell volume, blood glucose and lactate, plasma non-esterified fatty acids, insulin and cortisol were measured before, during and after surgery. The greatest met...
van Loon JP, Stienen PJ, Doornenbal A, Hellebrekers LJ.To determine whether epidurally derived evoked potentials (EPs) can be used to reliably assess nociception and antinociception in ponies. Methods: 7 ponies. Methods: EPs and electromyograms (EMGs) from the quadriceps femoris muscles were recorded simultaneously, following electrical stimulation applied to the distal portion of the hind limb. The effect of increasing stimulus intensity, conduction velocities of the stimulated nerves, effect of epidurally applied methadone, and effect of systemically administered propofol were evaluated. Results: In the EP and EMG waveforms, 2 distinct complexes...
