David Evans

Charles Sturt University · School of Animal and Veterinary Sciences

A discussion of the value of symmetry in Australian racehorses

Background: The need for a horse to be ridden while wearing a measurement device that allows unrestricted ventilation and gas exchange has hampered accurate measurement of its maximal oxygen consumption (V̇O2 max) under field conditions. Objectives: Design and validate a facemask with the potential to measure V̇O2 max accurately in the field. S...

Sedation is often required to perform pulmonary function testing (PFT) in horses, but drug effects may influence respiratory function. The current study was designed to characterise the effects of sedation and bronchodilator administration on absolute and relative indices of pulmonary function during eupnoeic respiration and carbon dioxide-induced...

Background Respiratory problems are common in horses, and are often diagnosed as a cause of poor athletic performance. Reliable, accurate and sensitive spirometric tests of airway function in resting horses would assist with the diagnosis of limitations to breathing and facilitate investigations of the effects of various treatments on breathing cap...

The purpose of this short report is to describe the influences on the pricing of Thoroughbred (TB) horses for the adult recreational riding market. Research into the association between horse breed and specific behaviours supports the view that some breeds are more reactive than others. There is anecdotal evidence that TBs may be more likely than o...

IntroductionThe ability to accurately assess equine oxygen consumption (VO2) under field conditions has been limited by the need for unrestricted gas exchange.Methods Two variations of a mask and an associated electronics control module (ECM) were designed to enable breath-by-breath measurement of airflows with two 8.0 cm diameter pneumotachometers...

Despite its likely role in the treatment of racehorses and their likelihood of being whipped when tired, the opinions and beliefs of jockeys surrounding whip use have not been explored under a scientific framework. We administered a questionnaire directly to jockeys in Australia (n = 806), Ireland (n = 178), and the United Kingdom (n = 265). This q...

Inflammatory airway disease (IAD) is common in racehorses, and is a cause of wastage in the industry. IAD has been diagnosed by measurement of percent neutrophils (N%) in tracheal aspirates (TA). The aim of this study was to investigate whether spirometric indices of pulmonary function were correlated with N% in TAs. Limits to breathing were measur...

Concerns have been expressed concerning animal-welfare issues associated with whip use during Thoroughbred races. However, there have been no studies of relationships between performance and use of whips in Thoroughbred racing. Our aim was to describe whip use and the horses' performance during races, and to investigate associations between whip us...

The ability to obtain breath-by-breath measures of ventilatory mechanics for the entirety of an exercise test, regardless of speed(s) or duration enables evaluations of equine ventilation during exercise that are necessary for assessments of performance. Evaluation of a new ergospirometer (Quadflow; QF) system's accuracy and repeatability for measu...

We sought a physiological marker of overtraining in horses, using commonly practised field and laboratory tests to allow early prediction and treatment of the syndrome. Thirteen Standardbred horses were trained as follows: phase 1 (endurance, 7 weeks), phase 2 (high intensity, 9 weeks) and phase 3 (overload, 18 weeks). In phase 3 the horses were di...

Twenty-three Thoroughbred racehorses that were presented for a standard incremental exercise test also performed a test at an intensity equivalent to 115% V̇O2max in an effort to evaluate their anaerobic capacity by measuring the maximal accumulated oxygen deficit (MAOD). Submaximal V̇O2 values for speeds 3 to 10 m/s and V̇O2max were determined for...

This study investigated the effects of increased fat consumption on aerobic and anaerobic performance. Eight Thoroughbred horses that had undergone a 9 week, 6 days/week conditioning programme were randomly divided into 2 groups, Group F (5 horses) and Group C (3 horses). For 2 weeks before the study all horses consumed a standard diet (2% fat) fed...

The principal aim of this study was to examine whether alterations in sweat composition occurred during training. Ten Thoroughbred horses were trained 6 days per week for 9 weeks on a treadmill (+10% slope), 5 at moderate intensity, (80–100% V̇O2max) and 5 at low intensity, (40–45 % V̇O2max). On Day 1 of training and at the end of weeks 1, 2, 5 and...

The effects of training intensity and duration on blood lactate concentrations during submaximal and after maximal treadmill exercise were investigated in 2 groups of 5 Thoroughbred horses. Horses were trained on a treadmill in either a ‘fast’ or ‘slow’ group. In the ‘fast’ group, all exercise after an initial warm-up was at speeds which resulted i...

We examined 106 Thoroughbred (TB) and 51 Standardbred (SB) racehorses that were presented because of poor performance. All horses were in training and had raced within 2 weeks of presentation. Horses were acclimatised (2–4 runs) and tested on a treadmill set at a 10% slope. The exercise test consisted of 3 min at 4 m/s, 2 min at 6 m/s, then 1 min s...

Muscle glycogen resynthesis rates were studied in 6 Standardbred geldings that were exercised on a treadmill inclined at 10% slope to deplete muscle glycogen prior to treatments. Each horse completed 15 min at 50% V̇O2max, 15 min at 70% V̇O2max, 5 min at 90% V̇O2max then rested for 30 min. This was followed by 6, 1 min sprints at 100% V̇O2max with...

Administration of oral fluids prior to exercise may provide a fluid ‘buffer’ supporting cardiorespiratory and thermoregulatory function during prolonged exercise. Six Standardbred horses, previously acclimatised to a treadmill and a respiratory gas collection mask, were used in a crossover study and were given ∼17.5 litres hypotonic commercial elec...

Acclimation to treadmill exercise and to a respiratory gas collection mask were studied in 3 groups of Thoroughbred or Standardbred horses. Heart rate and plasma lactate concentration were measured at rest and at the completion of each speed increment during a series of acclimating runs at 4, 6 and 8 m/s on a treadmill inclined at a 10% slope. No s...

We tested the hypothesis that training would result in more rapid increase in V̇O2 and V̇CO2 following the onset of submaximal exercise. Six Standardbred horses were used and trained at submaximal intensities for 5 weeks. Horses were trained 6 days per week on an inclined treadmill (10% slope) at intensities between 40 and 70% V̇CO2max. At the onse...

To describe the impact of age, sex, and musculoskeletal (MS) injury on three preparation-level measures of performance: (i) the duration of preparation, (ii) time from the beginning of the preparation until the first start in a race or barrier trial, and (iii) time from the first start until the end of the preparation. Daily training and injury dat...

To describe the incidence rate of musculoskeletal (MS) injuries and investigate the factors that influence recovery from MS injury in young Thoroughbred horses in Australia. Training and injury data were collected at fortnightly intervals from 14 trainers in New South Wales. Incidence rates were calculated for initial injuries stratified by age-cla...

Analysis of individual breaths after exercise has potential for pulmonary function testing. The aims of this study were to investigate the dependence of measurements of pulmonary function in single breaths on time postexercise and tidal volume (VT) after treadmill exercise. Five Thoroughbred horses without evidence of airway disease were used. Hors...

This review addresses the physiology of performance horses in the context of functional tests aimed at assisting clinicians in the search for explanations of the individual's limitations, actual or perceived as below expectation. The intention is to assist clinicians who are faced frequently by owners or trainers seeking explanations for poor perfo...

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Field based studies of changes in fitness are difficult to conduct in galloping Thoroughbreds. Measurements of heart rate (HR) and real time velocity with a global positioning system (GPS) could provide a method for routine field studies of fitness. To investigate measurements of fitness in the field without using multiple, standardised steps of in...

Running ability of Thoroughbred racehorses is correlated with maximal oxygen uptake, and the velocity at maximal oxygen uptake is highly correlated with the velocity at maximal heart rate (VHRmax). To investigate the relationship between VHRmax and racing performance, expressed as 'peak dollars earned per race start'. Heart rate (HR) and velocity w...

Intrapulmonary blood causes an inflammatory response. Modifying this inflammatory response may be useful in the treatment of exercise induced pulmonary haemorrhage (EIPH). To evaluate the efficacy of 3 treatments, an oral bronchodilator, inhaled steroid and oral steroid in modifying the cellular response to intrapulmonary blood inoculation. Experim...

Locomotor-respiratory coupled (LRC) breath types are a feature of galloping exercise in horses. Differences in breath type have been demonstrated during exercise in particular the 'big respiratory cycle' (BRC) and 'flow hesitation'. To investigate breath types during recovery and quantitatively investigate BRCs during exercise to understanding the...

Musculoskeletal injuries (MSI) in racehorses have been identified as the most common cause of lost training days and weeks spent resting at pasture. Several training-, track- and horse-related risk factors have been identified. However, there is no clear understanding of the inter-relationship between these factors. The aim of this longitudinal coh...

The welfare of horses in training for racing and competition can be compromised by errors of management of many processes. Lameness is usually identified, as the major problem facing horse trainers and high lameness rates in racehorses is a major welfare concern. Recent epidemiological studies have shed light on important environmental risk factors...

Electrolaryngeography was used to study the latencies of the thoracolaryngeal adductor reflex in Thoroughbred horses with and without recurrent laryngeal neuropathy (RLN). Latencies were compared in horses with grades 1 and 2 RLN, diagnosed by endoscopy in resting horses. The reliability of the measurements, effect of sedation and correlations of l...

This study investigated the reliability of measurements with a new equine ergospirometer (Quadflow). Heart rate and blood lactate responses during exercise in horses wearing the Quadflow and an open flow mask were also compared. The mean percentage error of the oxygen uptake measurements was 8.2% (range 2.1-12.5%). Percent error for peak expiratory...

Red blood cell hypervolaemia has been used for diagnosis of overtraining in racehorses, and has been suggested as a mechanism of this cause of loss of racing performance. The effects of overload training (OLT) on the plasma, blood and red cell volumes were investigated in a prospective study in 12 Standardbred horses. Measurements of blood volumes...

Interactive software has been developed on CD-ROM to facilitate learning of problem formulation, diagnostic methodology, and therapeutic options in dog and cat behavior problems. Students working in small groups are presented with a signalment, a case history, and brief description of the problem behavior as perceived by the client. Students then n...

Relationships between racing performance and plasma lactate and uric acid concentrations after racing were investigated in pacing Standardbred racehorses. The study was undertaken in order to better understand factors that limit racing performance. Twenty horses were tested after races of 1760 m and 28 horses after races over 2160 m. Blood samples...

The aim of this study was to investigate the heart rate and blood lactate responses to exercise in event horses in normal training, and to compare them to those encountered in eventing competition. It was hypothesised that the responses during exercise in the course of training for CCI*** events would be significantly different from those of the Cr...

Thirteen Standardbred horses trained intensively for 34 weeks and detrained for 12 weeks to investigate the effects of training, overtraining and detraining on muscle metabolites, buffering capacity and enzyme activities (CS, HAD and LDH). After a standardised exercise test to fatigue at 10 m/s (approximately 100% VO2max), there was significant dep...

The second day of a 3-day event is the most physically demanding of the 3 days. If this is performed under hot and humid environmental conditions, detrimental effects on cardiovascular and thermoregulatory function and, therefore, on exercise capacity, may occur due to exercise-induced dehydration. We hypothesised that the administration of fluid e...

This study was undertaken to invesigate the application of submaximal field tests in assessment of performance. A submaximal field exercise test consisting of 2 bouts of pacing for 1600 m, with 5 min rest or walking between runs was performed on Standardbred racehorses at 2 training centres (A and B). Performance indices were compiled for each hors...

In six normal adult horses, pulsed-wave Doppler sonographic inspections were made of the left and right lateral palmar proper digital artery (LPPDA) of each thoracic limb. Using a two-period, crossover design with repeated measures, each LPPDA was inspected on four occasions throughout the day over a 7 hour period and, on each occasion, with the li...

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. Arte...

The potential racing and locomotory profile of a Thoroughbred yearling should be taken into account for its training programme and racing career. A gait test has been designed to assist the trainer in this task. The aim of this study was to investigate the temporal and kinetic locomotory variables of Thoroughbreds at the gallop, in relationship to...

To describe the clinical abnormalities found on post-race examination of poorly performing Standardbreds. The results of 541 post-race veterinary examinations on Standardbreds were analysed. The horses were selected for examination by the stipendiary stewards on the basis of poor performance from a population of approximately 20,000 runners which c...

The associations between velocity during a standardized, submaximal 800-m exercise test and blood lactate concentration after exercise were investigated in Thoroughbred racehorses on sand and grass racetracks. Predicted lactate concentrations for each horse's exercise test velocity were calculated from the line of best fit derived from results at e...

Investigations of the equine peripheral vascular system have been constrained by the lack of a non-invasive method of examining the arteries and veins of the limbs of the conscious horse. Precise correlations were established between the gross anatomical features of the peripheral vessels and their B-mode sonographic appearance in each thoracic lim...

The effects of training and over-training on plasma cortisol and β-endorphin (βEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks...

The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17...

The aim of this study was to investigate the effects of reduced muscle glycogen concentration on some physiological and metabolic responses during moderate intensity treadmill exercise in horses. Six Thoroughbred geldings were randomly allocated to 2 treatments (protocols A and B) or control in a 3 x 3 replicated Latin square design. In protocol A,...

We investigated and compared arterial blood gas and ventilatory changes during rapid acceleration sprint and during incremental treadmill exercise. Seven clinically normal racehorses completed standardised incremental exercise tests and rapid acceleration tests at speeds calculated to elicit 115% V̇ o 2max . Arterial oxygen tension decreased (P<.00...

This experiment was undertaken to determine whether there were differences in cardiorespiratory, haematological and muscular responses in horses trained at either low or moderate intensities. Ten Thoroughbred horses previously rested in paddocks for 4 months were trained 5 days/week for 9 weeks. Horses were allocated randomly into fast or slow grou...

Basal concentrations of cortisol (CORT), beta-endorphin (ßEP), growth hormone (GH) and testosterone (T) and their disruption during 32 h of recovery after treadmill exercise were investigated in 4 geldings. Blood samples were collected from resting horses every 20 min between 0600–1000 and 1500–1900 h, and hourly between 1000–1500 h on 3 consecutiv...

Thirteen standard-bred horses were trained intensively for 34 weeks and detrained for 6 weeks to study skeletal muscle adaptations to prolonged training, overtraining and detraining. Training included endurance (phase 1, 7 weeks), high-intensity (phase 2, 9 weeks) and overload training (OLT) (phase 3, 18 weeks). During phase 3, horses were divided...

To compare the development of exercise-induced arterial hypoxemia in horses before and after training, and to determine whether increases in maximum oxygen uptake (VO2max) following training results in a greater degree of exercise-induced arterial hypoxemia. 13 three- to five-year-old. Standardbred geldings without clinical signs of respiratory or...

The relationship between different grades of laryngeal function, as assessed by endoscopy at rest, and the measurements of indices of gas exchange and exercise capacity was assessed during a standardised treadmill exercise test in 149 horses. Horses with abnormalities other than idiopathic laryngeal hemiplegia (ILH) were excluded from the study and...

Studies of physiological responses to exercise in the horse frequently describe the relationships between measured variables, such as heart rate and oxygen consumption measured against velocity of the animal. Treadmill laboratory facilities allow accurate control and measurement of the velocity of exercise. However, studies made on the track or in...

Thirteen standardbred horses were trained as follows: phase 1 (endurance training, 7 wk), phase 2 (high-intensity training, 9 wk), phase 3 (overload training, 18 wk), and phase 4 (detraining, 12 wk). In phase 3, the horses were divided into two groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequenc...

The aim of this study was to investigate correlations between lactate concentrations in equine whole blood and plasma measured with Accusport1 and Yellow Springs Instruments (YSI2) (2300) methods. The effect of packed cell volume (PCV) on the accuracy of Accusport was also investigated. Blood samples were collected from Thoroughbred horses at 5-10...

We hypothesised that hyperhydration before prolonged exercise would increase and maintain plasma volume (PV), assisting thermoregulation and cardiorespiratory function. In a cross-over design, 7 horses received ≈26 L (6% bodyweight) of isotonic fluid or nothing (control). Horses undertook 98 min of treadmill exercise at intensities eliciting 20-60%...

The potential role of the hypothalamic-pituitary-adrenocortical axis in the aetiopathogenesis of overtraining was investigated in a longitudinal training study. Plasma cortisol concentration was measured in Standardbred geldings before and after high-intensity training (control group) or overtraining (treatment group) at rest, in response to an inc...

The aim of this study was to investigate the effect of 31 weeks prolonged, intense training on the aerobic fitness of horses by measuring maximum oxygen uptake (VO2max). Thirteen Standardbred horses were trained on a treadmill for 31 weeks. The first 7 weeks consisted of endurance training and the other 24 weeks consisted of high intensity training...

The effect of grade of idiopathic laryngeal hemiplegia (ILH) in 149 horses (Thoroughbred and Standardbred) was assessed using treadmill exercise tests. Horses with abnormalities other than ILH observed at rest were excluded from the study and laryngeal function was graded according to an established system, with grade 1 being normal and grade 5 ind...

The aim of this study was to examine the effects of a decreased muscle glycogen concentration on metabolic and physiological responses to high intensity exercise. Six Thoroughbred geldings of age 5.8±0.5 years (mean±SEM) and body weight of 487±12 kg (mean±SEM) were randomly allocated to two treatments or control in a 3x3 Latin square repeated desig...

Significant alterations in plasma electrolyte concentrations have been reported in horses following prolonged exercise, resulting from loss of hypertonic sweat. Sweat was collected from 10 horses undergoing a 10 week training programme; 5 at moderate intensity, to speeds of 10 m/s and 5 at low intensity, to speeds of 5 m/s. Sweat was collected from...

We examined the effect of treadmill speed and incline on O2 uptake (VO2), CO2 production, heart rate (HR), plasma lactate concentration, economy of locomotion, stride frequency, and stride length. A further aim was to examine the relationships between HR and VO2 and lactate and VO2 and whether these relationships vary with alterations in treadmill...

Twenty-four Thoroughbred and twelve Standardbred racehorses aged between 2 and 6 years, presented for reported poor racing performance, underwent clinical exercise testing. During the last 10 s of exercise at each speed throughout an incremental speed exercise test on a treadmill inclined at a 10% slope, samples of arterial blood and expired gases...

We examined the effect of treadmill speed and incline on O2 uptake (VO2), CO2 production, heart rate (HR), plasma lactate concentration, economy of locomotion, stride frequency, and stride length. A further aim was to examine the relationships between HR and VO2 and lactate and VO2 and whether these relationships vary with alterations in treadmill...

The distribution of lactate between red blood cells (RBC) and plasma was examined at rest, during exercise and 30 min after exercise in six Standardbred horses. Lactate and water concentrations were measured in blood and plasma samples collected prior to exercise, during the last 15 s of each step of an incremental exercise test and at 5 min interv...

Thoroughbred horses have a high aerobic capacity, approximately twice that of elite human athletes. Whereas the aerobic capacity of horses can be accurately measured, there have been no measurements of anaerobic capacity. The aim of this study was to determine whether maximal accumulated O2 deficit (MAOD) could be measured in horses and used as an...

Vascular access ports were surgically placed, first in rabbits maintained under laboratory conditions, and then in koalas maintained in a wildlife park. The ports remained patent for 9 months in rabbits and for up to 13 months in the koalas and were removed successfully. They allowed collection of blood samples without assistance or disturbance in...

The influence of training on blood lactate concentrations during treadmill exercise and a 40-minute inactive recovery period was examined in seven trained and seven detrained thoroughbred horses. Lactate concentrations were measured in venous blood collected at the end of each exercise state, and at intervals for 40 minutes afterwards. Measurements...

The presence of abnormal T waves in three or more electrocardiographic leads has been used to diagnose the cause of poor race performance in horses. This study investigated the relationship between previous racing performance in Standardbred horses and T waves, and the effect of training on the T wave. Thirty‐two horses were electrocardiographed in...

The relationship between gait and the respiratory response to exercise was examined in five standardbred racehorses which exercised on a treadmill at a pace and a gallop. After an initial warm-up, respiratory rate and stride frequency were measured after one and two minutes of treadmill exercise at 80 per cent of maximal oxygen consumption (VO2max)...

Various cardiorespiratory and metabolic indices were assessed during treadmill exercise in Thoroughbred and Standardbred racehorses with T wave changes in 4 or more leads on the electrocardiogram or second-degree atrio-ventricular (AV) block, and in horses that had no abnormalities on clinical examination, resting electrocardiography or upper respi...

A standardised incremental exercise test was performed by 9 racehorses with idiopathic laryngeal hemiplegia (ILH), 1 horse with maxillary sinus cysts, 1 horse with epiglottic entrapment, 1 horse with a lesion on the vocal folds, and 1 horse with pharyngitis. Two of the horses with ILH were retested after laryngoplasty and ventriculectomy. The findi...

At 2 and 5 mins after an 800-m gallop, venous blood was collected from 26 Thoroughbred racehorses for measurement of blood lactate concentration, packed cell volume (PCV) and haemoglobin concentration. In addition, 14 racehorses were given a strenuous submaximal treadmill exercise test. Heart rates during and after exercise at 10 m/sec on a treadmi...

The effects of roughage source on metabolism and exercise capacity were investigated using 6, previously conditioned, mature thoroughbred horses in a cross-over experiment. The horses were assigned to either non-alfalfa or alfalfa roughage diets which were isocaloric. The diets were fed for 2 weeks, after which the horses were exercise tested and t...

Twenty-five Thoroughbred (TB) and 25 Standardbred (SB) stables were visited to determine their feeding practices. The ingredients of the main feed of the day for a mature gelding of average size in full training were weighted at each stable. Nutrient content of diets was calculated using published data for the individual ingredients. Results are ex...

We examined the effects of sodium bicarbonate in 6 Thoroughbred horses during submaximal and maximal treadmill exercise. Cardiorespiratory function was assessed together with the effect on exercise capacity by determining the run time to fatigue at maximal intensities. To discriminate between sodium bicarbonate's alkalinising effects and the fluid...

Cardiovascular and respiratory responses to submaximal exercise training were investigated in 6 thoroughbred racehorses. Oxygen uptake, heart rate (HR) and arteriovenous oxygen content difference were measured during incremental treadmill exercise tests, before and after 7 weeks of treadmill training. Cardiac output during exercise was calculated b...