Heart rate in horses is a physiological parameter that reflects the number of heartbeats per minute. It is an important indicator of cardiovascular function and can be influenced by factors such as exercise, stress, excitement, and health status. Monitoring heart rate provides valuable insights into the horse's physical condition and can aid in assessing fitness levels or detecting potential health issues. In equine practice, heart rate is often measured using stethoscopes, heart rate monitors, or electrocardiograms. This page compiles peer-reviewed research studies and scholarly articles that explore the determinants, measurement techniques, and implications of heart rate variations in equine health and performance.
Morton AJ, Blikslager AT.Although short-term survival rates following small intestinal resection reportedly range from 48-88%, there is little information on predicting which horse may or may not survive small intestinal (SI) resection and anastomosis. The aim of this study was to identify factors that contribute to nonsurvival in horses following small intestinal resection. Medical records of horses which recovered from anaesthesia following SI resection were reviewed. Clinical and surgical variables were evaluated for their association with short-term survival using logistic regression and were reported as odds rati...
Holcombe SJ, Berney C, Cornelisse CJ, Derksen FJ, Robinson NE.To determine the effect of a commercially available nasal strip on airway mechanics in exercising horses. Methods: 6 horses (5 Standardbreds and 1 Thoroughbred). Methods: Horses exercised on a treadmill at speeds corresponding to 100 and 120% of maximal heart rate with and without application of a commercially available nasal strip. Concurrently, tracheal pressures, airflow, and heart rate were measured. Peak inspiratory and expiratory tracheal pressures, airflow, respiratory frequency, and tidal volume were recorded. Inspiratory and expiratory airway resistances were calculated by dividing pe...
Belgrave RL, Hines MT, Keegan RD, Wardrop KJ, Bayly WM, Sellon DC.The development of ultrapurified hemoglobin-based oxygen carriers has eliminated many problems associated with whole-blood transfusions in other species. We hypothesized that the administration of polymerized ultrapurified bovine hemoglobin (PUBH) would result in improved hemodynamic parameters in ponies with normovolemic anemia without adverse effects on renal function or coagulation times. Normovolemic anemia was induced in 6 healthy adult ponies. Over a 3-day period, at least 45 mL/kg of whole blood was withdrawn from each pony until a target PCV of <12% was attained. Plasma was separate...
Merritt AM, Xie H, Lester GD, Burrow JA, Lorenzo-Figueras M, Mahfoud Z.To evaluate the reliability of a method for inducing colic via small intestinal distention in horses and to examine the analgesic potential of bilateral electroacupuncture (EAP) at the Guan-yuan-shu (similar to BL21) acupoint. Methods: 5 healthy adult horses, each with a gastric cannula. Methods: A polyester balloon connected to an electronic barostat was introduced into the duodenum via the gastric cannula. At 2 specified intervals (before and after commencement of EAP), the balloon was inflated to a barostat-controlled pressure that induced signs of moderate colic. Each inflation was maintai...
Hamlin MJ, Shearman JP, Hopkins WG.Various changes in physiological parameters are associated with overtraining, which can be a serious problem for human and equine athletes. A 34 week longitudinal study was conducted to investigate the effects of an acute training overload on physiological parameters in 10 Standardbred racehorses. After 24 weeks of training, horses received 8 weeks of increased workload, followed by 2 weeks recovery. Horses performed a 2400 m time trial and a progressive submaximal exercise test on alternate weeks. By the end of the heavy training period, the average time for the final 1200 m of the time trial...
Visser EK, van Reenen CG, van der Werf JT, Schilder MB, Knaap JH, Barneveld A, Blokhuis HJ.Forty-one Dutch Warmblood immature horses were used in a study to quantify temperamental traits on the basis of heart rate (HR) and heart rate variability (HRV) measures. Half of the horses received additional training from the age of 5 months onwards; the other half did not. Horses were tested at 9, 10, 21 and 22 months of age in a novel object and a handling test. During the tests, mean HR and two heart variability indices, e.g. standard deviation of beat-to-beat intervals (SDRR) and root mean square of successive beat-to-beat differences (rMSSD), were calculated and expressed as response va...
Freeman SL, Bowen IM, Bettschart-Wolfensberger R, Alibhai HI, England GC.The cardiovascular effects of romifidine, an alpha-2 adrenoreceptor agonist, were investigated in six horses using two doses (80 and 120 microg kg(-1)) in a cross-over study design. Cardiac index and mixed venous oxygenation were significantly decreased at 15 and 30 minutes after both doses of romifidine. Systemic vascular resistance was significantly increased with romifidine (120 microg kg(-1)). Arterial blood pressure increased initially and then gradually decreased; the doses of decrease was significant at 90 and 120 minutes with romifidine 80 and 120 microg kg(-1). There were minimal diff...
Voss B, Mohr E, Krzywanek H.The objectives of the present study were to investigate the effects of Aquatraining of horses (aqua-treadmill exercise; treadmill manufactured by Equitech - L.u.S. Equipment, Warendorf, Germany) on selected blood parameters [lactic acid concentration (mmol/l), haemoglobin content (g/l)] and on heart-rate variability (HRV) [heart rate (beats per min; b.p.m.), standard deviation of all NN-intervals (SDNN; ms), normalized power of the low and high frequency band (LFnorm, Hfnorm; au), % recurrence, % determinism and ratio(corr)]. Seven horses performed six exercise tests with different work loads ...
Hoff TK, Hood DM, Wagner IP.To evaluate the clinical efficacy of topically administered glyceryl trinitrate (GTN) for inducing digital submural vasodilation in clinically normal horses. Methods: 7 adult horses without foot abnormalities. Methods: A concurrent-control crossover design was used to determine whether topical application of GTN ointment for prevention or treatment of laminitis would result in a detectable increase in digital perfusion. Heat-acclimated horses instumented for detection of wall surface temperature (HWST), mean systemic pressure, and heart rate were used. Horses were exposed to cold to induce dig...
Goodrich LR, Nixon AJ, Fubini SL, Ducharme NG, Fortier LA, Warnick LD, Ludders JW.To determine whether preoperative epidural administration of morphine and detomidine would decrease postoperative lameness after bilateral stifle arthroscopy in horses. Methods: Prospective clinical controlled study. Methods: Eight adult horses that had bilateral arthroscopic procedures, including drilling of cartilage and subchondral bone within the femoropatellar joints. Methods: Horses were randomly separated into 2 groups. Preoperatively, 4 horses were administered a combination of epidural morphine (0.2 mg/kg) and detomidine (30 microg/kg), and 4 horses were administered an equivalent vol...
Smith GW, Constable PD, Foreman JH, Eppley RM, Waggoner AL, Tumbleson ME, Haschek WM.To determine whether cardiovascular dysfunction is evident in horses with leukoencephalomalacia experimentally induced by administration of fumonisin B1. Methods: 11 healthy horses of various breeds (body weight, 252 to 367 kg). Methods: Horses were randomly assigned to 3 groups and administered fumonisin B1 daily. Horses received IV injections of 0 (control horses; n = 4), 0.01 (3), or 0.20 mg (4) of fumonisin B1/kg for 7 to 28 days. Horses were examined daily for evidence of neurologic disease. When neurologic signs consistent with leukoencephalomalacia were evident, horses were anesthetized...
Irvine CH, McKeough VL, Turner JE, Alexander SL, Taylor TB.Our objectives were to determine whether repeated administration of prostaglandin F2alpha (PGF2alpha) to simulate the endogenous mode of secretion would be more effective than a single injection in inducing luteolysis and enable use of smaller doses less likely to cause adverse side effects. The main study comprised 43 dioestrous mares, who were given im. either a single 10 mg dose of natural PGF2alpha (n = 22) or 2 doses of 0.5 mg PGF2, 24 h apart (n = 21). The intensity of side effects was assessed in 8 dioestrous mares given 5, 1.5, 0.5 or 0 mg PGF2alpha in consecutive cycles. Two doses of ...
Manohar M, Goetz TE, Humphrey S, Depuy T.It has been suggested that pulmonary injury and inflammation-induced histamine release from airway mast cells may contribute to exercise-induced arterial hypoxemia (EIAH). Because stress failure of pulmonary capillaries and EIAH are routinely observed in exercising horses, we examined whether preexercise administration of an H1-receptor antagonist may mitigate EIAH. Two sets of experiments, placebo (saline) and antihistaminic (tripelennamine HCl at 1.10 mg/kg iv, 15 min preexercise) studies, were carried out on seven healthy, exercise-trained Thoroughbred horses in random order 7 days apart. A...
Couroucé A, Chrétien M, Valette JP.We hypothesised that the derived physiological variables V2 and V4 (velocity to achieve a blood lactate concentration of 2 and 4 mmol/l, respectively), HR2 and HR4 (the corresponding heart rate) and V200 (the velocity for a heart rate of 200 beats/min) would improve with training state and age, in French Trotters. A total of 194 French Trotters from one training establishment were followed for 6 years and 1105 standardised field exercise tests performed on a sand training track. The horses were divided into 6 age groups (from 1 to > or = 6 years) and 4 training groups (beginning, endurance tra...
van Loon G, Fonteyne W, Rottiers H, Tavernier R, Jordaens L, D'Hont L, Colpaert R, De Clercq T, Deprez P.The purpose of the present study was to develop a feasible and safe technique for dual-chamber pacemaker implantation in healthy horses. Implantation was performed in a standing, tranquilized horse and in ponies. Atrial and ventricular leads were transvenously inserted through the cephalic vein, and a subcutaneous pacemaker pocket was created between the lateral pectoral groove and the manubrium sterni in 6 equids. Positioning of each lead was guided by echocardiography and by measuring the electrical characteristics of the lead. The implantation procedure lasted about 4 hours in each animal a...
Ohmura H, Hiraga A, Aida H, Kuwahara M, Tsubone H.To investigate the effects of repeated atropine injection on heart rate (HR) variability in resting Thoroughbred horses, two microg/ kg of atropine as parasympathetic nervous blockade was injected intravenously every 6 min to a total of 8 microg/kg after intravenous administration of 0.2 mg/kg of propranolol as sympathetic nervous blockade. We recorded electrocardiograms and obtained the HR, then evaluated variation in HR from the power spectrum in terms of low frequency (LF, 0.01-0.07 Hz) power and high frequency (HF, 0.07-0.6 Hz) power. Administration of atropine decreased parasympathetic ne...
Richter MC, Bayly WM, Keegan RD, Schneider RK, Weil AB, Ragle CA.To determine the cardiovascular and respiratory effects of water immersion in horses recovering from general anesthesia. Methods: 6 healthy adult horses. Methods: Horses were anesthetized 3 times with halothane and recovered from anesthesia while positioned in lateral or sternal recumbency in a padded recovery stall or while immersed in a hydropool. Cardiovascular and pulmonary functions were monitored before and during anesthesia and during recovery until horses were standing. Measurements and calculated variables included carotid and pulmonary arterial blood pressures (ABP and PAP respective...
Wilkins PA, Gleed RD, Krivitski NM, Dobson A.Seven Standardbred horses were exercised on a treadmill at speeds (approximately 12 m/s) producing maximal heart rate, hypoxemia, and a mean pulmonary arterial pressure of approximately 75 mmHg. Extravascular lung water was measured by using transients in temperature and electrical impedance of the blood caused by a bolus injection of cold saline solution. Lung water was approximately 3 ml/kg body wt when standing but did not increase significantly with exertion. We conclude that any increase in fluid extravasation from the pulmonary hypertension accumulates in the lung at a level that is less...
Kollias-Baker C, Cox K, Jones J.Omeprazole is a proton-pump inhibitor recently approved in the United States for the treatment of gastric ulcer disease in horses. A study was designed to determine the effects of omeprazole treatment on the physiological indices of performance of horses during incremental treadmill exercise. In a crossover-design study carried out over 2 weeks, five horses completed standardized incremental exercise tests on a high-speed treadmill either with no treatment or treatment with omeprazole. No statistically significant effects of omeprazole were found on the mean maximum responses for specific oxyg...
Bettschart-Wolfensberger R, Bowen MI, Freeman SL, Feller R, Bettschart RW, Nolan A, Clarke KW.To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery. Methods: 10 ponies. Methods: After sedation was induced by IV administration of medetomidine (7 microg/kg of body weight), anesthesia was induced by IV administration of propofol 12 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 microg/kg per hour) and propofol 10.07 to 0.11 mg/kg per minute). Spontaneous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during...
Meyer GA, Lin HC, Hanson RR, Hayes TL.This study aimed to identify blood serum lidocaine concentrations in the horse which resulted in clinical signs of intoxication, and to document the effects of toxic levels on the cardiovascular and cardiopulmonary systems. Nineteen clinically normal mature horses of mixed breed, age and sex were observed. Lidocaine administration was initiated in each subject with an i.v. loading dose of 1.5 mg/kg bwt and followed by continuous infusion of 0.3 mg/kg bwt/min until clinical signs of intoxication were observed. Intoxication was defined as the development of skeletal muscle tremors. Prior to admi...
Manohar M, Goetz TE, Hassan AS, Rothenbaum P, Humphrey S.The present study was carried out to determine whether inhibition of nitric oxide (NO) synthase promotes anaerobic metabolism in exercising horses, resulting in a significantly increased blood lactate concentration. N(omega)-nitro-L-arginine methyl ester (L-NAME) is a potent inhibitor of NO synthase that has been tested in horses and other species. Two sets of experiments, namely placebo (saline control) and L-NAME (20 mg/kg, i.v.) studies, were carried out on seven healthy, sound, exercise-trained, Thoroughbred horses in random order, 6 to 7 days apart. In both experiments, an incremental exe...
Gangl M, Grulke S, Detilleux J, Caudron I, Serteyn D.Forty-eight horses subjected to elective surgery were randomly assigned to three groups of 16 horses. After premedication with 0.1 mg/kg acepromazine intramuscularly and 0.6 mg/kg xylazine intravenously, anaesthesia was induced either with 2 g thiopentone in 500 ml of a 10 per cent guaifenesin solution, given intravenously at a dose of 1 ml/kg (group TG), or with 100 mg/kg guaifenesin and 2.2 mg/kg ketamine given intravenously (group KG), or with 0.06 mg/kg midazolam, and 2.2 mg/kg ketamine given intravenously (group KM). Anaesthesia was maintained with isoflurane. The mean (sd) end tidal isof...
Manohar M, Goetz TE, Hassan AS.Because sensitivity of equine pulmonary vasculature to endogenous as well as exogenous nitric oxide (NO) has been demonstrated, we examined whether endogenous NO production plays a role in exercise-induced arterial hypoxemia. We hypothesized that inhibition of NO synthase may alter the distribution of ventilation-perfusion mismatching, which may affect the exercise-induced arterial hypoxemia. Arterial blood-gas variables were examined in seven healthy, sound Thoroughbred horses at rest and during incremental exercise protocol leading to galloping at maximal heart rate without (control; placebo...
Marlin DJ, Schroter RC, White SL, Maykuth P, Matthesen G, Mills PC, Waran N, Harris P.The aims of the present field-based study were to investigate changes in fit horses undergoing acclimatisation to a hot humid environment and to provide data on which to base recommendations for safe transport and acclimatisation. Six horses (age 7-12 years) were flown from Europe to Atlanta and underwent a 16 day period of acclimatisation. Exercise conditions during acclimatisation (wet bulb globe temperature index 27.6+/-0.0 [mean +/- s.e.]) were more thermally stressful compared with the European climate from which the horses had come (22.0+/-1.8, P<0.001). Following the flight, weight l...
Funkquist P, Sandhagen B, Persson SG, Hedenstierna G, Essén-Gustavsson B, Nyman G.Five Standardbred trotters with red cell hypervolaemia (RCHV) were compared before and after removal of approximately 22% (36 ml/kg bwt) of the total blood volume in order to evaluate the haemodynamic responses, haemorheological alterations and oxygen transport during exercise to fatigue. Data were recorded during submaximal exercise at 4 different speeds on a treadmill and then during continued running at the highest speed step until fatigue. Oxygen uptake (VO2), pulmonary artery pressure (PAP), systemic artery pressure (SAP), heart rate (HR), haematocrit and haemoglobin concentrations (Hb) w...
Ohmura H, Hiraga A, Aida H, Takahashi T, Nukada T.To determine oral dosage and to evaluate the pharmacokinetics in horses of orally administered flecainide, an antiarrhythmic drug, the correlations between its plasma concentration and PR, QRS and QT intervals in equine electrocardiograms (ECG) were investigated. Six healthy horses were administered a randomly ordered dose of 4 or 6 mg/kg of flecainide acetate. The ECG was monitored (heart rate (HR), PR, QRS, and QT intervals) and blood was taken at timed intervals to measure the plasma flecainide concentrations pre- and post-administration. The maximum plasma concentration reached 1014+/-285 ...
Yamanaka T, Oku K, Koyama H, Mizuno Y.To clarify time-related changes in equine cardiovascular system during maintenance anesthesia (180 min, 1.2 minimum alveolar concentration) with sevoflurane (Sev-group) compared to isoflurane (Iso-group) as the basis for clinical use of Sev, horses were examined for the heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), systemic vascular resistance (SVR) and pre-ejection period (PEP)/ejection time (ET) that is an index of the cardiac contractility. The HR was almost 30 beats/min in both groups without significant temporal change. MAP was significantly elevated with time but the...
Fugaro MN, Coté NM.To determine whether location and type of small intestinal anastomosis and other variables were associated with short- and long-term survival rates in horses undergoing stapled small intestinal anastomosis. Methods: Retrospective study. Methods: 84 horses that underwent small intestinal anastomosis. Methods: Medical records from 1988 to 1997 were examined for horses that underwent stapled small intestinal anastomosis. Horses were allotted into 4 groups: jejunojejunostomy (n = 27), jejunoileostomy (11), jejunoileocecostomy with small intestinal resection (20), and jejunoileocecostomy without sm...
Hoffmann KL, Wood AK, Griffiths KA, Evans DL, Gill RW, Kirby AC.The effects of feeding on blood flow to the equine foot are poorly understood. In a temperature-controlled room, duplex Doppler ultrasonographic observations were made pre- and postprandially of the lateral proper palmar digital artery of 5 horses, randomly assigned to twice and 4 times daily feeding in an unbalanced 2 period crossover design. Arterial diameter and blood velocity were measured over 4 h and additional observations made of heart rate, blood pressure, total plasma protein, packed cell volume, plasma glucose and insulin. There was no effect of the feeding regimen on any variable. ...
Pérez R, Recabarren SE, Mora G, Jara C, Quijada G, Hetz E.In order to establish the relationship between draught force and cardiorespiratory responses to exercise heart rate (HR), respiratory rate (RR), arterial and venous blood gases, pH, hemoglobin concentration and temperature were measured in five draught horses during rest, immediately after exercise and 30 min post-exercise under field conditions. A wagon equipped with an odometer and a hydraulic dynamometer was used for measuring distance and draught force. The wagon was loaded with 946 kg for the low load, 1,979 kg for the medium load and 2,994 kg for the high load, and drawn for a distance o...
Ryan A, Gurney M, Steinbacher R.A 10-year-old 466 kg mustang gelding presented to an equine referral hospital for surgical repair of nasal, frontal and lacrimal bone fractures from an unknown trauma. Surgical repair was performed under general anaesthesia, including a right-sided maxillary regional anaesthetic block with mepivacaine hydrochloride. Progressive hyperkalaemia was documented perianaesthetically (T-3 mins; 134 mins after induction; potassium 6.4 mmol/L (ref 3.5-5.1 mmol/L). Perianaesthetic bradycardia was attributed to alpha -2 agonist infusion administration, and other characteristic ECG changes (flattened ...
Ishigami N, Horiba K.A 41-year-old woman presented with symptoms of cardiac tamponade. Diagnosis of a primary malignant tumor in the right atrium without distant metastasis was made by echocardiography, computed tomography and coronary angiography. Aggressive surgery consisting of resection of the tumor including the right atrial wall together with the right coronary artery and sinus node was performed. This was followed by coronary artery bypass grafting with myocardial electrode implantation for reconstruction of the right atrial wall using an equine pericardium. Final diagnosis was of angiosarcoma by pathologic...
Hedberg Y, Dalin AM, Ohagen P, Holm KR, Kindahl H.In various species, sex, hormonal treatments and oestrous-cycle stage have been shown to affect the animal's response in behavioural tests. Few such studies have been performed in the horse. The main aim of the present study was to investigate whether oestrous-cycle stage affects mares' response to a novel object test and isolation test and, in part, to study whether mares, assumed to suffer from oestrous-related behavioural problems, respond differently in these tests when compared with controls. Twelve mares were tested twice, in oestrus and dioestrus, in a crossover design. Seven behavioura...
Grubb T, Edner A, Frendin JH, Funkquist P, Rydén A, Nyman G.To assess oxygenation, ventilation-perfusion (V/Q) matching and plasma endothelin (ET-1) concentrations in healthy horses recovering from isoflurane anaesthesia administered with or without pulse-delivered inhaled nitric oxide (iNO). Methods: Prospective experimental trial. Methods: Healthy adult Standardbred horses. Methods: Horses were anaesthetized with isoflurane in oxygen and placed in lateral recumbency. Six control (C group) horses were anaesthetized without iNO delivery and six horses received pulse-delivered iNO (NO group). After 2.5 hours of anaesthesia isoflurane and iNO were abrupt...
Dahl S, Cotrel C, Leleu C.A retrospective study concerning spontaneous active recovery intensity, i.e. at a freely chosen speed, after a submaximal exercise in trotters showed that the mean intensity demanded by trainers corresponds to 40-50% of maximal heart rate (max HR; unpublished data). However, in human athletes, optimal active recovery intensity was found to be about 60-70% of max HR. Is the spontaneous recovery optimal after a submaximal exercise in trotters? Objective: To compare different recovery intensities and define the most efficient one. Methods: Thirty-seven trotters performed a standardised exercise t...
Nyman G, Björk M, Funkquist P.To investigate the gas exchange response during exercise in horses with mild bronchiolitis (MB), we studied 7 Standardbred trotters. In order to determine pulmonary gas exchange and red cell volume in relation to bodyweight (CV/BW), submaximal graded exercise tests were performed. VO2 was monitored from an open bias flow system without valves. Heart rate, respiratory rate and mean pulmonary and systemic artery pressures were measured. Cardiac output and alveolar ventilation were calculated. Arterial and mixed venous blood were drawn for blood gas analysis and pH measurements. Pulmonary gas exc...
Lucas Castillo JA, Gozalo-Marcilla M, Werneck Fonseca M, Possebon FS, da Rosa AC, de Araujo Aguiar AJ.Information on appropriate protocols for sedation of Nordestino donkeys is scarce. Objective: To evaluate the sedative and cardiorespiratory effects of low doses of intravenous (i.v.) xylazine with and without acepromazine in 'Nordestino' donkeys. Methods: Seven healthy female Nordestino donkeys (150 ± 18 kg) were included in this blinded, randomised, crossover experiment. Methods: Four treatments were administered, consisting of two i.v. injections, at baseline (T0, 1st injection) and 15 min later (T15, 2nd injection). Treatments included acepromazine 0.05 mg/kg bwt + saline (AS), saline + x...
Allen GK, Campbell-Beggs C, Robinson JA, Johnson PJ, Green EM.Six, clinically healthy horses, of mixed age and sex, were infused via a jugular venous catheter with 100 ml of pyrogenfree sterile saline (PFSS; 0.9% NaCl). Animals were infused with Escherichia coli O55:B5 endotoxin (total dose = 50 ng/kg bwt), 24 (LPS-1) and 48 h (LPS-2) after PFSS infusion. Blood was collected before, and every 15 min after, each infusion for the first 8 h and then every 2 h for the following 14 h. Clinical responses (rectal temperature, heart rate, respiration rate and blood pressure) were determined before and every 4 h after each infusion for 20 h. Geometric mean anti-e...
Irvine CH, McKeough VL, Turner JE, Alexander SL, Taylor TB.Our objectives were to determine whether repeated administration of prostaglandin F2alpha (PGF2alpha) to simulate the endogenous mode of secretion would be more effective than a single injection in inducing luteolysis and enable use of smaller doses less likely to cause adverse side effects. The main study comprised 43 dioestrous mares, who were given im. either a single 10 mg dose of natural PGF2alpha (n = 22) or 2 doses of 0.5 mg PGF2, 24 h apart (n = 21). The intensity of side effects was assessed in 8 dioestrous mares given 5, 1.5, 0.5 or 0 mg PGF2alpha in consecutive cycles. Two doses of ...
Törneke MK, Ingvast-Larsson JC, Johansson JM, Appelgren LE.To determine pharmacokinetics of terbutaline in healthy horses and to relate serum terbutaline concentrations with the drug's pharmacodynamic effects. Methods: 6 healthy horses. Methods: Horses were given terbutaline i.v. (10 microg/kg of body weight) and, 1 week later, p.o. (100 microg/kg). Responses to drug administration (eg, heart rate and serum lactate concentration) were measured. Serum terbutaline concentration was measured by means of gas chromatography with mass spectrometry. Protein binding was determined in vitro. Results: Following i.v. administration, median maximum serum terbutal...
Pagan JD, Harris PA.There is considerable debate among horsemen about how to feed horses before exercise. Should horses be fed or fasted before work and when should hay be fed relative to grain and/or exercise? Three experiments were conducted to evaluate if feeding hay with and without grain affects glycaemic and haematological responses in Thoroughbred (TB) horses at rest and during a simulated competition exercise test (CET) on a high-speed treadmill. In Experiment 1, 6 TB horses were fed hay at 3 different times relative to a grain meal. Time of feeding hay affected glycaemic response, plasma protein and wate...
Čebulj-Kadunc N, Frangež R, Kruljc P.Scientific studies on the physiological responses of young horses to workloads are limited. Therefore, the aim of our study was to determine the basal values of some cardiovascular, thermoregulatory, hematological, and biochemical parameters in 10 purebred Lipizzan fillies aged 4 years in the initial phase of training, and their responses to a graded workload, i.e., by lunging for 15 min in four exercise tests at 2-week intervals. The basal values of the measured parameters were within a range for warm-blooded horses and mostly increased after exercise in all four exercise tests. Resting heart...
Ebisuda Y, Mukai K, Takahashi Y, Yoshida T, Kawano A, Matsuhashi T, Miyata H, Kuwahara M, Ohmura H.Heat acclimatization or acclimation training in horses is practiced to reduce physiological strain and improve exercise performance in the heat, which can involve metabolic improvement in skeletal muscle. However, there is limited information concerning the acute signaling responses of equine skeletal muscle after exercise in a hot environment. The purpose of this study was to investigate the hypothesis that exercise in hot conditions induces greater changes in heat shock proteins and mitochondrial-related signaling in equine skeletal muscle compared with exercise in cool conditions. Fifteen t...
Arcaro I, Fischer BL, Lascola KM, Clark-Price SC.To investigate the effects of intravenous (IV) administration of terbutaline on PaO, PaCO, pH, heart rate (HR) and arterial pressures in healthy, laterally recumbent horses breathing ambient air under total intravenous anesthesia (TIVA). Methods: Prospective experimental study. Methods: Eight healthy adult horses were enrolled. Six horses, four mares and two geldings weighing 433-624 kg, completed the study. Methods: Horses were sedated with xylazine (1.0 mg kg) IV for placement of arterial and venous catheters. Anesthesia was induced with midazolam (0.1 mg kg) and ketamine (2.2 mg kg) IV and ...
Young LE, Blissitt KJ, Clutton RE, Molony V, Darke PG.Transoesophageal Doppler echocardiography was performed in 7 Thoroughbred horses anaesthetised with halothane. The procedure was performed on 4 occasions under standard conditions. On one occasion dobutamine hydrochloride was infused at 4 micrograms/kg/min for 20 min. Recordings of aortic blood velocity, obtained using high pulsed repetition frequency Doppler echocardiography (HPRF), were used to derive maximum acceleration (dv/dtmax), maximum velocity (Vmax), left ventricular ejection time (ET), pre-ejection period (PEP), velocity time integral (VTI) and cardiac output (CO). The coefficient o...
Pallarols NB, Lamuraglia R, Guglielminetti A, Ortiz de Elguea MF, Carossino M, Funcia JP.Xylazine and remifentanil in constant rate infusion (CRI) could be used for sedation in horses without adverse effects. The objective was to evaluate behavioral and cardiopulmonary effects of an intravenous (IV) infusion of xylazine and remifentanil for sedation in horses. Xylazine (0.8 mg/kg IV) followed after 3 minutes by a CRI of xylazine and remifentanil (0.65 mg/kg/h and 6 μg/kg/h, respectively) was administered in 10 healthy horses for 60 minutes. Sedation, ataxia, and cardiopulmonary, hematological, and blood gases variables were evaluated. Heart rate decreased significantly durin...
The Journal of physiologyFebruary 9, 2006
Volume 572, Issue Pt 1 155-164 doi: 10.1113/jphysiol.2006.105635
O'Connor SJ, Ousey JC, Gardner DS, Fowden AL, Giussani DA.This study investigated, in vivo, the mechanisms underlying the development of cardiovascular function in the horse fetus, with particular relevance to baroreflex function and hind limb vascular arterial reactivity to constrictor agonists. Under general anaesthesia, vascular catheters were inserted and a Transonic flow probe was implanted around one of the metatarsal arteries of 13 horse fetuses, either at 0.6 of gestation (n= 6) or at 0.9 of gestation (n= 7, term approximately 335 days). At least 5 days after surgery, pressor, vasoconstrictor and cardiac chronotropic responses to exogenous bo...
Ebert M, Moore-Colyer MJS.The aim of this study was to estimate the energy requirements of performance horses in active, variable training in the field. Sixty horses in England and Switzerland were measured over 2-wk periods and, for 15 of these, the measurement period was extended, ranging from 21 to 42 wk. Energy intake was estimated by measuring daily feed consumption. Energy output was measured using heart rate (HR) monitors during 608 training sessions, relating HR to volume of oxygen (VO₂) and converting VO₂ to energy. Field maintenance requirements were calculated by deducting the marginal energy cost of tra...
Kollias-Baker CA, Court MH, Williams LL.To determine the effects of yohimbine and tolazoline on the cardiovascular, respiratory and sedative effects of xylazine, four horses were sedated with xylazine and treated with either yohimbine, tolazoline or saline. Xylazine was administered as an intravenous (i.v.) bolus (1.0 mg/kg) followed by a continuous infusion at the rate of 12 micrograms/kg/min. Heart rate, respiratory rate, mean arterial pressure, arterial blood gases, and the chin-to-floor distance were recorded throughout the experiment. After 60 min, either yohimbine or tolazoline was administered i.v. in incremental doses until ...
Hinchcliff KW, McKeever KH, Schmall LM, Kohn CW, Muir WW.We investigated the effects of 1 h of sustained submaximal exertion on the renal and systemic hemodynamics of six horses. The horses ran on a treadmill at a speed that produced heart rates of 55-60% of each horse's maximum heart rate. Exertion produced heart rates of 121 +/- 6.6 and 126 +/- 6.1 (SE) beats/min after 15 and 60 min, respectively. Cardiac output increased significantly (P less than 0.05) from 70.1 +/- 3.1 to 246.2 +/- 4.7 ml.min-1.kg body wt-1 after 15 min of exertion and thereafter did not change. There was no significant change from rest in p-aminohippuric acid and creatinine cl...
Gottlieb-Vedi M, Persson S, Erickson H, Korbutiak E.The purpose of this study was to determine if training with short intervals at the velocity producing a lactate level of 4 mmol/l (VLA4) is sufficient to induce adaptations and better exercise tolerance. Five Standardbred mares (4-8 years) were interval trained on a treadmill 3 days a week for 12 weeks and subsequently detrained for 4 weeks. Standardized exercise tests were performed before, during and after the training period and muscle biopsies were taken. Measurements were made of heart rate, oxygen consumption, stride frequency, blood volume and blood lactate. Plasma volume was reduced af...
Ohtani N, Kitagawa K, Mikami K, Kitawaki K, Akiyama J, Fuchikami M, Uchiyama H, Ohta M.There are many obvious health benefits to riding, including developing a strong core and legs, but there are also many less obvious benefits, such as increased confidence and introspection. Few studies have addressed the effects of horseback riding on children and the mechanisms underlying how riding affects humans. We examined the effects of horseback riding on the ability to distinguish Go/No-go tasks and solve arithmetic problems in children. Methods: The subjects were 34 boys and 72 girls, aged 10-12 years old, which were divided into three groups (horse riding, walking, and resting). Th...
Sandersen CF, Detilleux J, de Moffarts B, Van Loon G, Amory H.The aim of this study was to investigate the effect of combined atropine low-dose dobutamine stress test on left ventricular parameters in adult warmblood horses, to establish a potential protocol for pharmacological stress echocardiography. Seven healthy untrained warmblood horses aged 9 to 22 years were used. Heart rate (HR) and left ventricular B- and M-mode dimensions were recorded at baseline and during stress testing with 35 microg/kg atropine IV followed by incremental dobutamine infusion of 2 to 6 microg/kg/min. HR increased significantly (P < .05) during the pharmacological challen...
Daunt DA, Dunlop CI, Chapman PL, Shafer SL, Ruskoaho H, Vakkuri O, Hodgson DS, Tyler LM, Maze M.Cardiopulmonary and behavioral responses to detomidine, a potent alpha 2-adrenergic agonist, were determined at 4 plasma concentrations in standing horses. After instrumentation and baseline measurements in 7 horses (mean +/- SD for age and body weight, 6 +/- 2 years, and 531 +/- 48.5 kg, respectively), detomidine was infused to maintain 4 plasma concentrations: 2.1 +/- 0.5 (infusion 1), 7.2 +/- 3.5 (infusion 2), 19.1 +/- 5.1. (infusion 3), and 42.9 +/- 10 (infusion 4) ng/ml, by use of a computer-controlled infusion system. Detomidine caused concentration-dependent sedation and somnolence. The...
Gold JH, Schuder JC, Stoeckle H.The defibrillation effectiveness of 4-msec rectangular wave shocks was evaluated using myocardial electrodes with 25-kg dogs and (nominally) 100-kg calves, ponies, and pigs as part of an evaluation of the suitability of these animals as models for automatic implanted defibrillator research. The percent success of defibrillation attempts in dogs ranged from 44% with 4-A, 6-J shocks to 93% with 8-A, 16-J shocks. The success achieved in calves with scaled electrodes was uniformly lower and reached a maximum of 28% with 23-A, 107-J shocks. Pigs defibrillated with scaled electrodes at a success lev...
Muñoz A, Santisteban R, Rubio MD, Riber C, Agüera EI, Castejón FM.To establish the effect of the locomotor pattern on heart rate (HR) and plasma lactate (LA), 28 horses, 18 Andalusian (AN) and 10 Anglo-Arabian (AA), aged 3-4 years, were studied. After a warm-up period, the horses performed a four-step test at 5, 6, 7 and 8 m/s, covering 1000 m at each velocity. HR was monitored, LA was analysed at rest and after each workload, and images were filmed. The locomotor parameters determined were stride duration (SD), frequency (SF) and length (SL), step and bipedal support durations, stance (restraint and propulsion) and swing phase durations, and stride vertical...
Zeitler-Feicht MH, Streit S, Dempfle L.Comparison with regard to animal welfare of different automatic feeding systems for hay and concentrate in group housing systems for horses using parameters of ethology and physiology. Methods: Parameters of research comprised: duration of stay, frequency of visit, threatening behaviour with and without risk of injury, and avoiding behaviour as well as heart rate and injuries of the integument. 452 horses were observed at the feeding area of 32 run-out-sheds. Every group of horses was continuously observed following the pie chart system for 24 hours. Results: The "walk-through" station signifi...
Jansson A, Nyman S, Lindholm A, Lindberg JE.Studies of the effect of varying dietary carbohydrate compositions on exercise metabolism of horses are scarce. In the present study, the starch and sugar proportions were altered in the diet to 4 Standardbred horses. In a crossover experiment, the horses were offered a hay and oat diet, where the oats were substituted for barley syrup (BS) at 4 levels (BS 0, 0.5, 1.0 and 1.5 kg). Each diet was consumed for 21 days and both an incremental treadmill exercise test (IE) and a 40 min submaximal exercise test (SE) were performed. During the IE there was a significant (P<0.05) increase in mean VO...
Rose RJ, Allen JR, Brock KA, Clark CR, Hodgson DR, Stewart JH.Five standardbred geldings received intravenous clenbuterol hydrochloride and saline in a crossover experiment to evaluate the effects of clenbuterol on certain cardiorespiratory parameters during and after treadmill exercise. The exercise test consisted of four steps. Step 1 at a speed of 76 m per minute, step 2 at 129 m per minute, step 3 at 190 m per minute and step 4 at 236 m per minute. The duration of each step was two minutes, except step 4 which was four minutes. The treadmill was set at a grade of 19 per cent. Before exercise, 30 minutes after clenbuterol or saline administration, art...
