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.
Alvarez AV, Schumacher J, DeGraves FJ.OBJECTIVE To determine whether addition of epinephrine to a lidocaine solution would prolong and potentiate the efficacy of a palmar digital nerve block (PDNB) in horses. ANIMALS 6 adult horses with naturally occurring forefoot lameness. PROCEDURES Initially, a PDNB with a 2% lidocaine solution was performed on the affected foot of each horse. Three days later, the PDNB was repeated with a 1% lidocaine solution or a 1% lidocaine solution containing epinephrine (dilution, 1:200,000). After another 3-day washout period, the PDNB was repeated with the treatment opposite that administered for the ...
Zuber N, Zuber M, Schwarzwald CC.Assessment of cardiac electromechanical function in horses requires training, experience and specialised equipment and does not allow continuous monitoring over time. Objective: The objective of this study was to establish the use of an acoustic ECG monitor (Audicor ) in healthy horses. It provides noninvasive, examiner-independent, continuous analyses combining ECG and phonocardiography to calculate indices of cardiac mechanical activity and haemodynamics. Device usability was investigated, reference intervals calculated and reproducibility of analyses assessed. Methods: Prospective descripti...
Piccione G, Giudice E, Giannetto C, Mortola JP.Heart rate (FH) accelerates in inspiration and decelerates in expiration, a phenomenon known as Respiratory Sinus Arrhythmia (RSA). Although the presence of RSA has been documented in many species, how its magnitude compares among species is unknown. We asked whether the magnitude of RSA in a large mammal, the horse, differed from that of previously measured humans. From electrocardiogram and pneumography, the peaks and troughs of FH were identified breath-by-breath in four horses (Italian Saddlebred geldings) during resting wakefulness. RSA was computed as the peak-trough FH difference, in pe...
Janczarek I, Stachurska A, Wilk I, Krakowski L, Przetacznik M, Zastrzeżyńska M, Kuna-Broniowska I.Touching the skin by gentle stroking is frequently used to reward horses. The objective of the study was to examine emotional excitability and behaviour of horses in response to stroking different regions of their bodies. The study included 15 adult warmbloods and 15 adult ponies, nine geldings and six mares within each type of horse. First, a novel-object test was conducted. For five successive days, one of five regions of the horse's body was stroked on each side for 5 min. Heart rate and heart rate variability were monitored at rest, during the test and stroking. Simultaneously, horse beha...
Carstensen H, Hesselkilde EZ, Fenner M, Loft-Andersen AV, Flethøj M, Kanters JK, Sattler SM, Tfelt-Hansen J, Pehrson S, Jespersen T, Buhl R.Pharmacological treatment of atrial fibrillation (AF) in horses can be challenging because of low efficacy and adverse effects. Flecainide has been tested with variable efficacy. Objective: To test whether the efficacy of flecainide is dependent on AF duration. Methods: Nine Standardbred mares. Methods: Factorial study design. All horses were instrumented with a pacemaker and assigned to a control or an AF group. On day 0, all horses were in sinus rhythm and received 2 mg/kg flecainide IV. Atrial fibrillation subsequently was induced in the AF group by pacemaker stimulation. On days 3, 9, 27, ...
Bohák Z, Harnos A, Joó K, Szenci O, Kovács L.It is generally accepted that besides cortisol concentrations, parameters of heart rate variability (HRV) are appropriate indicators of stress in horses. The aim of this study was to determine anticipatory stress in eight Standardbred stallions participating in harness race. Cortisol and HRV responses to a mild exercise performed in training circumstances were compared to a maximal effort exercise performed in real trotting race conditions. Parameters of HRV reflecting vagal (root mean square of the successive differences, RMSSD) and sympathetic nervous system activity (ratio of the low and hi...
Gehlen H, Bildheim LM.Our aim was to evaluate the influence of the ageing process on the myocardium using pulsed wave tissue Doppler (PW-TDI) and colour tissue Doppler imaging (cTDI) to measure myocardial velocities at three different myocardial regions (right ventricular free wall: RVFW, interventricular septum: IVS, left ventricular free wall: LVFW). A total of 60 healthy warmblood horses, aged from 3 to 30 years, were examined. The horses were divided into five age groups (group 1: 3-8 years, n = 14; group 2: 9-13 years, n = 9; group 3: 14-18 years, n = 10; group 4: 19-23 years, n = 14; group 5: 24-...
Knych HK, McKemie DS, Seminoff K, Hartmann P, Hovda L, Benson D.Ethylphenidate is a psychostimulant and analog of the commonly prescribed compound, methylphenidate (Ritalin®). There are a limited number of studies describing the disposition and pharmacologic/toxicological effects of ethylphenidate in any species. The abuse potential in equine athletes along with the limited data available regarding administration in horses necessitates further study. The objectives of the current study were to describe drug concentrations, develop an analytical method that could be used to regulate its use, and describe the pharmacodynamic effects of ethylphenidate in hor...
Aarnes TK, Lerche P, Bednarski RM, Hubbell JAE.This study evaluated use of midazolam, ketamine, and xylazine (MKX) for total intravenous (IV) anesthesia (TIVA) in horses. Medical records of 46 horses undergoing a clinical procedure using MKX for TIVA were reviewed. Age, breed, procedure, heart rate (HR), respiratory rate (RR), pre-anesthetic drugs, induction drugs, and total volume of MKX were recorded. Duration of anesthesia, time to standing, number of attempts to stand, and recovery score were also recorded. All horses were premedicated with an alpha-2 adrenoceptor agonist and anesthesia was induced with ketamine and midazolam. Duration...
Neuhauser S, Gösele P, Handler J.During the peripartal period, interpretation of basic clinical signs may be challenging. In the present study, heart rate (HR), respiratory rate (RR) and body temperature (BT) were evaluated in healthy mares of different breed types and compared to reference values for adult horses from the literature. Methods: During daily physical exams of periparturient mares, the HR, RR and BT were evaluated. Differences according to the horse's size were investigated and in large breeds, the influence of dystocia or retained placenta was analysed. Results: During the last weeks before parturition (a. p.),...
Baldwin AL, Chea I.This study explored whether aromatherapy increases the parasympathetic component (root mean square of successive differences [RMSSD]) of heart rate variability (HRV) in horses. Horses are highly sensitive, easily stressed, have an acute sense of smell, and have been shown to benefit from aromatherapy. The protocol, performed on eight dressage horses, followed a crossover design with an experimental treatment of humidified essential oil (lavender, Lavandula angustifolia) and a control treatment of humidified air. Heart rate variability was recorded for 7 minutes before, during, and immediately...
Rowland AL, Glass KG, Grady ST, Cummings KJ, Hinrichs K, Watts AE.To determine the influence of epidural detomidine and morphine on serum corticosteroid concentrations and pain-related behavioral responses in mares during and after ovariectomy via colpotomy. Methods: Blinded prospective study. Methods: Nine university-owned mares. Methods: Five of 9 horses received caudal epidural detomidine hydrochloride (0.01 mg/kg) and morphine sulfate (0.1 mg/kg) prior to surgery. All horses received local anesthetic around the ovarian pedicle, 0.02 mg/kg butorphanol IV at the start of the procedure and after first ovary removal, were sedated as required throughout the p...
Abass M, Picek S, Garzón JFG, Kühnle C, Zaghlou A, Bettschart-Wolfensberger R.In horses castration with primary intention healing is usually performed under balanced inhalation anaesthesia. To optimise analgesia, the use of local anaesthesia was tested. Objective: To investigate the effect of local mepivacaine before castration with first intention healing under balanced medetomidine-isoflurane anaesthesia and flunixin meglumine, morphine analgesia on perioperative cytokine levels and pain in horses. Methods: Prospective blinded clinical study. Methods: Twenty stallions were randomly assigned to control or mepivacaine groups. Flunixin meglumine was administered before s...
Buhl R, Carstensen H, Hesselkilde EZ, Klein BZ, Hougaard KM, Ravn KB, Loft-Andersen AV, Fenner MF, Pipper C, Jespersen T.Atrial fibrillation (AF) is the most common arrhythmia affecting performance in horses. However, no previous studies have quantified the performance reduction in horses suffering from AF. Objective: To quantify the effect of AF on maximum velocity (Vmax ), maximum heart rate (HRmax ), heart rate recovery (T100 ), hematologic parameters and development of abnormal QRS complexes. Methods: Nine Standardbred trotters. Methods: Two-arm controlled trial. Six horses had AF induced by means of a pacemaker and 3 served as sham-operated controls. All horses were subjected to an exercise test to fatigue ...
Kanz P, Krieger S, Drillich M, Iwersen M.Pulse oximetry is a well-established technique in human and veterinary medicine. In farm animals, it could also be a useful tool for the detection of critical conditions relating to oxygen supply and the cardiovascular system. Among other uses, an innovative application could be the monitoring of fetuses during birth. This could help in the early identification of critical situations and support farmers and veterinarians in their decision to start obstetric or life-support interventions. Until now, however, its use in ruminant medicine was still limited to experimental applications. The object...
Neudeck S, Kästner SBR, Wittenberg-Voges L, Rohn K, Hopster K.OBJECTIVE To determine global and peripheral perfusion and oxygenation during anesthesia with equipotent doses of desflurane and propofol combined with a constant rate infusion of dexmedetomidine in horses. ANIMALS 6 warmblood horses. PROCEDURES Horses were premedicated with dexmedetomidine (3.5 μg•kg, IV). Anesthesia was induced with propofol or ketamine and maintained with desflurane or propofol (complete crossover design) combined with a constant rate infusion of dexmedetomidine (7 μg•kg •h). Microperfusion and oxygenation of the rectal, oral, and esophageal mucosa were measured bef...
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...
Tapio HA, Raekallio MR, Mykkänen A, Mama K, Mendez-Angulo JL, Hautajärvi H, Vainio OM.OBJECTIVE To compare the effects of MK-467 and hyoscine butylbromide on detomidine hydrochloride-induced cardiorespiratory and gastrointestinal changes in horses. ANIMALS 6 healthy adult horses. PROCEDURES Horses received detomidine hydrochloride (20 μg/kg, IV), followed 10 minutes later by MK-467 hydrochloride (150 μg/kg; DET-MK), hyoscine butylbromide (0.2 mg/kg; DET-HYO), or saline (0.9% NaCl) solution (DET-S), IV, in a Latin square design. Heart rate, respiratory rate, rectal temperature, arterial and venous blood pressures, and cardiac output were measured; blood gases and arterial plas...
Kiely MA, Warrington GD, Mcgoldrick A, O'loughlin G, Cullen S.Jockeys should maintain a high level of physical fitness to meet the physical demands of horse racing. The aim of this study was to determine the physiological requirements of the riding gaits used regularly in training. Methods: Eleven trainee jockeys performed a maximal incremental Wattbike cycle ergometer test. Mean absolute and relative oxygen uptake (VO2) and heart rate (HR) were recorded for the steady-state period during a walk, trot and canter. Energy expenditure (EE) and associated metabolic equivalent (MET) were also estimated. Results: During a walk, trot and canter, relative mean V...
Shawaf T, Hussen J, Al-Zoubi M, Hamaash H, Al-Busadah K.The Shetland ponies, which originate from harshest environments in the world islands in the north of the Atlantic Ocean, are now most popular pony breed distributed in almost every corner of the world. Reference ranges of physiological, biochemical and haematological values, which are widely used in veterinary clinics, may differ according to season, age, sex, type of feeding, and environmental circumstances of the area. Reference ranges of haematological and biochemical values of Shetland ponies are rare. The present study was therefore undertaken to evaluate the impact of season, age and sex...
Padalino B, Raidal SL, Knight P, Celi P, Jeffcott L, Muscatello G.This study aimed to document the effects of an eight hour journey on behavioural, clinical, haematological, environmental and respiratory parameters, and to identify possible associations between factors. Twelve horses underwent clinical examination, respiratory endoscopy with tracheal wash (TW) aspiration, and collection of venous and arterial blood before (BJ) and after the journey (AJ). TW were submitted for conventional quantitative bacteriological evaluation and genetic microbiome analyses. Behaviour was assessed in stables prior to transportation and throughout the journey. Transportatio...
De Clercq D, Broux B, Vera L, Decloedt A, van Loon G.In human and veterinary medicine, monophasic action potential (MAP) analysis and determination of local refractory periods by contact electrode technique gives valuable information about local cardiac electrophysiological properties. It is used to investigate dysrhythmias and the impact of drugs on the myocardium. Precise measurement of total MAP duration is difficult, therefore the MAP duration is usually determined at a repolarization level of 90% (APD90). Until now, no studies are published about the feasibility of this technique in the standing non-sedated horse. In 6 healthy Warmblood hor...
Li M, Chadda KR, Matthews GDK, Marr CM, Huang CL, Jeevaratnam K.Exercising horses uniquely accommodate 7-8-fold increases in heart rate (HR). The present experiments for the first time analysed the related adaptations in action potential (AP) restitution properties recorded by in vivo telemetric electrocardiography from Thoroughbred horses. The horses were subjected to a period of acceleration from walk to canter. The QRS durations, and QT and TQ intervals yielded AP conduction velocities, AP durations (APDs) and diastolic intervals respectively. From these, indices of active, λ = QT/(QRS duration), and resting, λ0 = TQ/(QRS duration), AP wavelengths wer...
Decloedt A, Broux B, De Clercq D, Deprez P, Van Steenkiste G, Vera L, Ven S, van Loon G.Based on its pharmacokinetic profile and electrophysiological effects in healthy horses, sotalol potentially could be used as a long-term PO antiarrhythmic drug in horses. Objective: To evaluate the effect of sotalol on heart rate (HR), QT interval, atrial fibrillatory rate, and success of cardioversion in horses with naturally occurring chronic atrial fibrillation (AF). Methods: Twenty-eight horses referred for transvenous electrical cardioversion of AF were treated with 2 mg/kg sotalol PO q12h for 3 days before cardioversion, and 13 horses underwent the same protocol without sotalol administ...
Knych HK, Seminoff K, McKemie DS, Kass PH.Acepromazine is a tranquilizer used commonly in equine medicine. This study describes serum and urine concentrations and the pharmacokinetics and pharmacodynamics of acepromazine following intravenous, oral, and sublingual (SL) administration. Fifteen exercised adult Thoroughbred horses received a single intravenous, oral, and SL dose of 0.09 mg/kg of acepromazine. Blood and urine samples were collected at time 0 and at various times for up to 72 hr and analyzed for acepromazine and its two major metabolites (2-(1-hydroxyethyl) promazine and 2-(1-hydroxyethyl) promazine sulfoxide) using liqu...
Malinowski K, Yee C, Tevlin JM, Birks EK, Durando MM, Pournajafi-Nazarloo H, Cavaiola AA, McKeever KH.With the increase in the number of horses being used in Equine-Assisted Activities and Therapies (EAAT) programs and with the increasing concern for animal welfare, it is important to understand the impact of such interventions on the stress level and quality of life for the horses involved. The purpose of the present pilot study was to test the hypothesis that participation in EAAT would acutely alter physiological markers of stress and well-being, including plasma cortisol, plasma oxytocin, and heart rate variability (HRV), in horses and that symptoms of posttraumatic stress disorder (PTSD) ...
Negro S, Bartolomé E, Molina A, Solé M, Gómez MD, Valera M.The stress level is suggested to have a negative effect on horses during equestrian competitions, specifically in trotter racing. The main objectives of this study were to measure stress levels in Spanish Trotter Horse races with a reliable non-invasive method, and determining the threshold level of stress that leads to the best performance results and also shows when the stress perceived by the horse becomes distress. One hundred and thirty individuals were evaluated, measuring their performance (based on racing time per kilometre (TPK)) and their stress (based on eye temperature, assessed wi...
Gunther-Harrington CT, Arthur R, Estell K, Martinez Lopez B, Sinnott A, Ontiveros E, Varga A, Stern JA.Exercise induced cardiac fatigue (EICF) and cardiac dysrhythmias are well described conditions identified in high-level human athletes that increase in frequency with intensity and duration of exercise. Identification of these conditions requires an understanding of normal pre- and post-race cardiac assessment values. The objectives of this study were to (1) characterize selected indices of cardiac function, electrophysiologic parameters, and biochemical markers of heart dysfunction prior to and immediately after high level racing in Thoroughbred horses receiving furosemide; and (2) create pre...
Wilson KAT, Raisis AL, Drynan EA, Lester GD, Hosgood GL.To determine agreement between invasive blood pressures measured in three peripheral arteries in anaesthetized horses undergoing elective surgery. Methods: Prospective balanced incomplete block design. Methods: A total of 18 client-owned horses. Methods: Invasive blood pressure (IBP) was measured simultaneously in one of the following three combinations: 1) transverse facial and facial artery; 2) transverse facial and metatarsal artery; and 3) facial and metatarsal artery. The agreement in blood pressure measured for each combination was performed in six horses. At each sample time, systolic (...
Connysson M, Muhonen S, Jansson A.This study investigated the effects of transport and diet on metabolic response during a subsequent race-like test in Standardbred horses in training fed a forage-only diet and a 50:50 forage:oats diet. Six trained and raced Standardbred trotter mares were used. Two diets, 1 forage-only diet (FONLY) and 1 diet with 50% of DM intake from forage and 50% from oats (FOATS), were fed for two 29-d periods in a crossover design. At Day 21, the horses were subjected to transport for 100 km before and after they performed an exercise test (transport test [TT]). At Day 26, the horses performed a control...
Cabiddu R, Borghi-Silva A, Trimer R, Trimer V, Ricci PA, Italiano Monteiro C, Camargo Magalhães Maniglia M, Silva Pereira AM, Rodrigues das Chagas G....Neurological disorders are associated with autonomic dysfunction. Hippotherapy (HT) is a therapy treatment strategy that utilizes a horse in an interdisciplinary approach for the physical and mental rehabilitation of people with physical, mental and/or psychological disabilities. However, no studies have been carried out which evaluated the effects of HT on the autonomic control in these patients. Therefore, the objective of the present study was to investigate the effects of a single HT session on cardiovascular autonomic control by time domain and non-linear analysis of heart rate variabilit...
Knych HK, Casbeer HC, McKemie DS, Arthur RM.Butorphanol is a narcotic analgesic commonly used in horses. Currently, any detectable concentration of butorphanol in biological samples collected from performance horses is considered a violation. The primary goal of the study reported here was to update the pharmacokinetics of butorphanol following intravenous administration, utilizing a highly sensitive liquid chromatography-mass spectrometry (LC-MS) assay that is currently employed in many drug-testing laboratories. An additional objective was to characterize behavioral and cardiac effects following administration of butorphanol. Ten exer...
Buhl R, Ersbøll AK, Eriksen L, Koch J.The purpose of this study was to assess the intraobserver variation of various echocardiographic measures in standardbred trotters. Serial echocardiographic examinations were carried out on eight standardbred mares by one ultrasonographer for 5 separate days. During each examination, five nonconsecutive cardiac cycles (frames) were recorded and an average obtained for each individual measure. Various echocardiographic measures were obtained by use of two-dimensional (2-D), M-mode, color flow Doppler and pulsed wave Doppler echocardiography. The total variation in the echocardiographic measurem...
Ducharme NG, Hackett RP, Gleed RD, Ainsworth DM, Erb HN, Mitchell LM, Soderholm LV.We hypothesized that changes in pleural pressure induced by resistive breathing would affect transmural pulmonary artery, pulmonary capillary, and pulmonary wedge pressures. Seven horses were assigned to exercise with each of 4 upper respiratory resistive loads in random order at intervals of at least 2 days: 1) control--no added resistive loads; 2) inspiratory resistive load (Iobst)--left laryngeal hemiplegia; 3) expiratory resistive load (Eobst)--one-way valve in the right nostril; and 4) combined inspiratory and expiratory resistive loads (CIEobst)--left nostril occlusion. On each occasion,...
Parks CM, Manohar M.Transmural distribution of myocardial blood flow and coronary vasodilator reserve (15-microns-diam radionuclide-labeled microspheres) was studied in 11 adult, healthy ponies at rest and during moderate and severe exercise performed on a treadmill (heart rate 56 +/- 4, 154 +/- 3, and 225 +/- 7 beats . min-1, respectively.). Exercise resulted in a marked increase in cardiac output, mean aortic pressure, right ventricular (RV) systolic and end-diastolic pressure, left ventricular (LV) end-diastolic pressure, and the maximum rate of rise of LV pressure LV (dP/dtmax). Accompanying these changes was...
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...
Corletto F, Raisis AA, Brearley JC.The aim of this study was to compare two different alpha2 agonist-opioid combinations in ponies undergoing field castration. Methods: Prospective double-blind randomized clinical trial. Methods: Fifty-four ponies undergoing field castration. Methods: The ponies were randomly allocated to receive one of three different pre-anaesthetic medications [intravenous (IV) romifidine 100 microg kg(-1) and butorphanol 50 micro kg(-1); romifidine 100 microg kg(-1) and morphine 0.1 mg kg(-1) IV, or romifidine 100 microg kg(-1) and saline IV] before induction of anaesthesia with ketamine 2.2 mg kg(-1) IV. F...
Rose RJ, Purdue RA, Hensley W.The effects of prolonged strenous exercise on the plasma concentrations of sodium, potassium, calcium, chloride, bicarbonate, phosphate, albumin, cholesterol, glucose, creatinine, bilirubin, alkaline phosphatase, creatine phosphokinase, lactic dehydrogenase and asparate amino transferase were studied in a group of 26 horses competing in an endurance ride. There were significant changes in most parameters, when control values were compared with those taken immediately after the ride. There was also a significant correlation between several biochemical parameters and heart rate taken 30 minutes ...
Muir WW, Skarda RT, Sheehan WC.The cardiopulmonary effects of the narcotic agonists morphine, meperidine, oxymorphone, and methadone and of the partial agonist pentazocine were examined in the pain-free adult horse. The drugs produced dysphoric followed by euphoric effects. Increases in heart rate, arterial blood pressure, and cardiac output were observed in all horses with all drugs. Arterial blood pressure remained increased even after heart rate and cardiac output had returned to base-line values. Respiratory rate generally remained unchanged or increased shortly after drug administration and then decreased insignificant...
Elfenbein JR, Sanchez LC, Robertson SA, Cole CA, Sams R.To evaluate the effects of detomidine on visceral and somatic nociception, heart and respiratory rates, sedation, and duodenal motility and to correlate these effects with serum detomidine concentrations. Methods: Nonrandomized, experimental trial. Methods: Five adult horses, each with a permanent gastric cannula weighing 534 +/- 46 kg. Methods: Visceral nociception was evaluated by colorectal (CRD) and duodenal distension (DD). The duodenal balloon was used to assess motility. Somatic nociception was assessed via thermal threshold (TT). Nose-to-ground (NTG) height was used as a measure of sed...
Evans DL, Rose RJ.Six detrained Thoroughbred horses performed incremental treadmill tests. Maximal oxygen uptake (VO2max) was measured during exercise by analysis of expired gas. The relationships between oxygen consumption (VO2) and work rate, heart rate (HR), cardiac output (Q), stroke volume (SV) and arteriovenous oxygen content difference [C(a-v)O2] were examined during submaximal and maximal exercise. The relative contributions of blood flow and extraction of oxygen from muscle capillaries were assessed during exercise at VO2max. Mean VO2max was 129.7 +/- 2.9 (mean +/- S.E.M.) ml kg-1 min-1, which occurred...
Flores J, Corvera Poiré E, del Rio JA, López de Haro M.We consider a simple model to give a plausible mechanical explanation of what are the actual resting heart rates of mammals optimized for. We study what is the optimal frequency for a viscoelastic fluid circulating in a pulsatile way through a network of tubes and conclude that the heart rate is not optimized to transport blood through the whole net. Rather, actual resting heart rates of mammals happen at frequencies that optimize flow in vessels of radii that correspond to large arteries, which bring oxygenated blood rapidly far away from the heart, towards head and limbs. Our results for the...
Rovira S, Muñoz A, Rodilla V.Scaling in biology is usually allometric, and therefore, the size of the heart may be expressed as a power function of body weight (BW). The present research analyses the echocardiographic measurements in 68 healthy Spanish foals weighed between 70 and 347kg in order to determine the correct scaling exponent for the allometric equation. The echocardiographic parameters measured were: left ventricular internal dimensions (LVID), free wall thickness (LVFWT), interventricular septum thickness (IVST) at systole (s) and diastole (d), EPSS (distance between the point E of the mitral valve and the in...
Johns I, Tennent-Brown B, Schaer BD, Southwood L, Boston R, Wilkins P.The incidence and implications of positive blood cultures in mature horses with diarrhoea is unknown. The diagnosis of bacteraemia may alter treatment and prognosis. Objective: The proportion of horses with diarrhoea that are blood culture positive is higher than previously assumed and a positive blood culture has a negative impact on survival. Methods: Blood cultures were taken at admission and 24 h after admission from 31 mature horses with diarrhoea. Results: Nine (29%) horses were blood culture positive within 24 h of admission. Organisms isolated included Corynebacterium spp. (n = 6), Str...
Portier KG, Jaillardon L, Leece EA, Walsh CM.To evaluate the effects of local anaesthesia with lidocaine for castration of horses under intravenous anaesthesia. Methods: Prospective, randomized, blinded clinical trial. Methods: Fifteen equidae, scheduled to undergo castration under total intravenous anaesthesia, were randomly distributed in two groups. One group received lidocaine injections (group L: two ponies, four horses, two donkeys) and the other received saline (group S: two ponies, three horses, two donkeys). Methods: Behaviour, heart rate (HR) and respiratory rate (f(R)) were evaluated prior to anaesthesia. Body mass was measure...
Bayly WM, Gabel AA, Barr SA.Seven healthy, unexercised, previously trained, adult Standardbred horses were allotted to 2 groups and trained 78 days on a treadmill set at a 7 degree 30' angle. The groups were trained on different schedules, and the effects of training on heart rate, cardiac output, stroke volume, arteriovenous oxygen difference, systemic blood pressure, and venous lactic acid were determined. Measurements were made at rest, during exercise on the treadmill at rates of 55 m/min, 75 m/min, 100 m/min, and 154 m/min, and at 5 minutes after exercise (standardized exercise test). Heart rate and cardiac output d...
Johnston C, Gottlieb-Vedi M, Drevemo S, Roepstorff L.The Standardbred trotter must pull a considerable load when racing and, consequently, draught loading is a common method of training in the Standardbred and the effects of loading and fatigue due to loading on the locomotor pattern was the purpose of this investigation. Four mature healthy Standardbred horses trotted with and without a horizontal-pulling loading of 34 kg until the horses were no longer willing to keep pace with the treadmill despite encouragement. Heart rate was monitored every min using a bipolar electrocardiogram. The kinematics for 5 consecutive strides were filmed. Horses ...
Abass M, Picek S, Garzón JFG, Kühnle C, Zaghlou A, Bettschart-Wolfensberger R.In horses castration with primary intention healing is usually performed under balanced inhalation anaesthesia. To optimise analgesia, the use of local anaesthesia was tested. Objective: To investigate the effect of local mepivacaine before castration with first intention healing under balanced medetomidine-isoflurane anaesthesia and flunixin meglumine, morphine analgesia on perioperative cytokine levels and pain in horses. Methods: Prospective blinded clinical study. Methods: Twenty stallions were randomly assigned to control or mepivacaine groups. Flunixin meglumine was administered before s...
Durongphongtorn S, McDonell WN, Kerr CL, Neto FJ, Mirakhur KK.To compare hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of halothane and isoflurane in horses undergoing arthroscopic surgery. Methods: 8 healthy adult horses. Methods: Anesthesia was maintained with isoflurane or halothane (crossover study). At 6 intervals during anesthesia and surgery, cardiopulmonary variables and related derived values were recorded. Recovery from anesthesia was assessed; gastrointestinal tract motility was subjectively monitored for 72 hours after anesthesia. Horses were administered chromium, and fecal chromium concen...
Hobo S, Yoshida K, Yoshihara T.Equine respiratory patterns during swimming were examined in five normal horses. The experiment included a preliminary warming-up stage and 6 circuits of swimming around an annular pool of a 50-meter-circumference. The horses were examined for respiratory rates, intratracheal pressures, inspiratory time (TI), expiratory time (TE), respiratory cycle (T; TI + TE), heart rates, blood lactate concentrations, hematocrit and blood gases. The respiratory rates were maintained around 25/min. Blood gas values changed significantly during swimming. The intratracheal pressures during expiration and inspi...
Marntell S, Nyman G.The clinical and cardiorespiratory effects of premedication with acepromazine, butorphanol or diazepam in addition to romifidine before induction of anaesthesia with ketamine were studied in 6 horses on 4 random occasions. Administration of romifidine alone or in combination with butorphanol resulted in an increase in arterial blood pressure, accompanied by a significant decrease in heart rate with second-degree atrio-ventricular heart block. Induction of anaesthesia with ketamine returned the heart rate to baseline value, but the arterial blood pressure was significantly increased compared to...
Kohn CW, Hinchcliff KW, McKeever KH.To determine whether body temperature of horses exercised in hot, humid conditions and then repetitively washed with cold water will decrease more rapidly than that of horses that are not washed, and to determine whether washing with cold water has deleterious effects on horses. Methods: 5 physically fit Thoroughbred mares, 3 to 10 years old. Methods: Horses were exercised on a high-speed treadmill in hot (31.1+/-0.3 C), humid (relative humidity, 77.7+/-2%) conditions. Exercise was terminated when pulmonary artery temperature reached 41.5 C. Values for pulmonary artery, rectal, and left glutea...
Escudero A, González JR, Benedito JL, Prieto FR, Ayala I.Limited information exists regarding electrocardiographic parameters in clinically healthy donkeys. The study was carried out in 75 healthy adult animals (40 females and 35 males) using the Einthoven standard II and base-apex leads. The P wave showed usually a bifid shape deflection. The QRS complex of the donkeys appeared in several forms: QR and R were the most frequent in limb lead II, and QS and QR in the base-apex lead. Most T waves presented a simple negative configuration in lead II and biphasic shape in the base-apex one. Mean heart rate value was 52 beats per minute. The direction of ...
Evans DL, Rose RJ.The measurement of heart rate during exercise in the horse has been recommended as a means of prescribing work effort, monitoring the changes in aerobic capacity during training and as part of the clinical examination of the performance horse. The accuracy of four heart rate meters (PEH 100, PU 10, HR 14 and HRM-7) was assessed by comparison with heart rate determined by simultaneous telemetry electrocardiography (ECG) using a rapid incremental exercise test on a treadmill. Heart rate displayed by all four meters showed significant correlations with the ECG heart rate, but only two meters (PEH...
Powell BB, Horvath KC, Gilliam TL, Sibille KT, Keil A, Miller-Cushon EK, Wickens CL, Brooks SA.The startle response can be defined as a reflexive reaction to the sudden appearance of a novel stimulus that influences the survival and resilience of animals. In domesticated species, the behavioral component of the startle response can, in some cases, cause serious injury to the animal or human handlers if inappropriately expressed. Here, we describe a longitudinal study in a population of stock-type horses that quantified behavioral startle responses elicited by the presentation of a sudden novel object (rapidly opening umbrella). The study was performed in weanling foals across four conse...
Jansen F, Van der Krogt J, Van Loon K, Avezzù V, Guarino M, Quanten S, Berckmans D.The objective of this research was to develop a non-invasive method to detect an emotional response of a horse to novelty during physical activity. Two horses performed 20 trials each, in which the horse's heart rate (HR) and physical activity were continuously measured. The relationship between the horse's physical activity and HR was described by a mathematical model allowing online decomposition of the horse's HR into a physical component and a component containing information about its emotional state. Exposure to the novel object resulted in an increase in the emotional component of HR, w...
Decloedt A, Van Steenkiste G, Vera L, Buhl R, van Loon G.Atrial fibrillation (AF) is suspected by an irregularly irregular rhythm during auscultation at rest and should be confirmed by electrocardiography. Heart rate monitoring is potentially interesting for AF detection by horse owners, based on the disproportionally high heart rate during exercise or increased heart rate variability. Echocardiography and laboratory analysis are useful to identify underlying cardiac disease. Horses with severe cardiac disease should not undergo cardioversion due to the risk of recurrence. Cardioversion is recommended especially in horses performing high intensity e...
Skarda RT, Muir WW.Seven adult mares were used to determine the analgesic, CNS, and cardiopulmonary effects of detomidine hydrochloride solution after epidural or subarachnoid administration, using both regimens in random sequence. At least 1 week elapsed between experiments. A 17-gauge Huber point (Tuohy) directional needle was used to place a catheter with stylet into either the epidural space at the first coccygeal interspace or the subarachnoid space at the lumbosacral intervertebral junction. Catheters were advanced so that the tips lay at the caudal sacral (S5 to S4) epidural space or at the midsacral (S3 ...
Viry S, De Graaf JB, Frances JP, Berton E, Laurent M, Nicol C.The relationship between the biomechanical horse–rider interaction and endurance race performance requires further investigation. Objective: To characterise, both quantitatively and qualitatively, elite and advanced horse–rider dyads on the basis of the biomechanical horse–rider interaction during endurance races. Methods: Five elite and 5 advanced horse–rider dyads were recorded during CEI*/CEI** endurance races using 2 synchronised triaxial accelerometers each placed close to horse and rider centres of mass. Methods: For each horse–rider dyad, analyses focused on the vertical displ...
Buntenkötter S, Deegen E.Cardioversion through varying quinidine sulphate treatments was achieved in 3 riding horses with auricular fibrillation. The horses were subjected to continual telemetric ECG registration before and after reversion in a uniform exercise-tolerance-test. A comparison of the heart rate curves showed a strong decline of the heart beat frequency during the exercise phase after synchronisation. The decrease in heart rate during exercise was greater than 30% in all 3 patients. Anti-arrhythmic treatment is, therefore, recommended for horses with auricular fibrillation and without concurrent heart dise...
