The Use of Treadmills Within the Rehabilitation of Horses

Treadmills and water treadmills are found in research centers, therapy centers, and are becoming increasingly common in private competition yards, yet little evidence exists which informs their use for rehabilitation of injury. The control that they afford in terms of speed, intensity, and duration of exercise is attractive, but guidance regarding any possible benefits and/or contraindications for treadmill exercise in any given scenario is limited. In this review, the evidence pertaining to the physiology and biomechanics of treadmill exercise in horses is examined and combined with our experiences of using treadmills for rehabilitation over 15 years to offer some basic guidelines as to their use. Evidence is presented to support the use of a land treadmill in the rehabilitation of horses following various distal limb conditions and back pain. The effects of water treadmill exercise on limb and back kinematics are considered and suggestions made as to how to select the most appropriate water depth for various conditions. Successful rehabilitation depends as much on avoidance of unsuitable exercise as selection of beneficial exercise. In time, more evidence regarding the use of treadmills for specific conditions will accrue; but as horses commonly suffer from multiple conditions (e.g., hindlimb lameness and back pain), it is likely that a rationale devised on a case by case basis will always be necessary, with regular monitoring of the gait pattern throughout rehabilitation.     

The use of sports medicine techniques in evaluating the problem equine athlete

Discovering the cause of poor performance in racehorses can often represent a considerable challenge eluding the more common diagnostic techniques available at the racetrack. Application of sports medicine techniques to these problem cases can aid in the diagnosis of poor performance. Central to the development of this capability has been the use of highspeed treadmills, allowing the racehorse to be evaluated in the controlled laboratory setting, at exercise intensities equivalent to those of racing. Video and cinematographic gait analysis can be used in the diagnosis of subtle lameness conditions. Evaluating hoof balance at high speed has also become an important technique for both lameness diagnosis and prevention. Correcting hoof imbalance normalizes the applied stresses on joints, ligaments, and tendons. Abnormal upper airway function resulting in increased resistance to airflow is major cause of poor racing performance. Often this cause of upper airway dysfunction is difficult to evaluate at rest or after exercise. A definitive diagnosis can be made in these cases using treadmill endoscopy to visualize upper airway function during peak exercise. Lower airway function can also affect performance capability. Radiographic and scintigraphic imaging modalities can be used to evaluate both global and regional lung function in cases of suspected pneumonia, EIPH, COPD, or emphysema. Reduced metabolic fitness can be a primary cause of poor performance due to inherent differences in capability, pathologic changes in the major body systems involved in exercise, or inadequate training. Metabolic stress testing can be used to evaluate the level of fitness in these cases. Orthopedic imaging has also become a valuable diagnostic technique for evaluating musculoskeletal injuries. Scintigraphic evaluation of soft tissue and bone and CT scanning are used to localize the source of lameness and to grade the severity of various orthopedic conditions such as arthritis and stress-induced bone disease that are often difficult to categorize with conventional radiography.     

The use of high-speed treadmills for lameness and hoof balance evaluations in the horse

Examination for lameness remains the most important component of the clinical evaluation for poor performance. Although conventional examinations can be used to diagnose many causes of lameness, treadmill video gait analysis and dynamic hoof balance evaluations have proved to be useful not only for evaluating lameness but also for maintenance of long-term soundness. Treadmill lameness evaluations offer a major advantage compared to conventional evaluations because of the stationary position of the exercising horse relative to the people performing the examination. Lameness is suspected if asymmetric motion is observed or asymmetric sounds of the feet contacting the tread surface are heard during the treadmill evaluation. Localization of lameness to the front or hind legs is the first step in the treadmill gait analysis protocol. In trotting and pacing horses, asymmetric movements associated with foreleg lameness generally are confined to the front end. In contrast to the pacing gait, asymmetric movements associated with hindlimb lameness can involve both the front and rear of the horse at the trot. The evaluation is continued to determine which side of the horse is abnormal. Viewed from the front, horses with primary forelimb lameness appear to have an asymmetric downward rotation of the torso, head, and neck away from the stiffer lame front leg toward the flexed normal leg as it contacts the tread surface. The lame hind leg can appear to be stiff relative to the opposite normal leg. This results in uneven side-to-side oscillations of the pelvis rotating away from the abnormal stiff-appearing hind leg toward the normal, flexed hind leg as it contacts the tread surface. Both front- and hind-leg lamenesses cause dissociation of the normal foot-fall sequence, resulting in the alteration of the normal two beat gait at the trot or the pace to a three-beat gait. The final step of the lameness examination involves the use of diagnostic regional anesthesia to determine the anatomic location of the lameness. Treadmill video gait analysis can be used to evaluate differences in the horse's gait before and after each anesthetic block. Optimal foot balance during exercise is critical for long-term maintenance of musculoskeletal soundness. Combining slow-motion video gait analysis with treadmill exercise provides an excellent method for evaluating hoof balance at a variety of speeds. Optimal hoof balance can be achieved by using the technique of successive trimming and re-evaluation. The principles of hoof balancing include establishing dorsopalmar or dorsoplantar hoof balance.(ABSTRACT TRUNCATED AT 400 WORDS)     

Current Knowledge of Equine Water Treadmill Exercise: What Can We Learn From Human and Canine Studies?

Equine water treadmills (WTs) are increasingly being found in research and therapy centers and private competition yards. However, the programs incorporating WT exercise for training and rehabilitation of horses are mainly based on anecdotal evidence due to the lack of scientific evidence available. This review aims to evaluate what is currently known about WT exercise for horses drawing on what is known from human and canine investigations. Studies of WT exercise have demonstrated that water depth, temperature, and speed have a significant effect on physiological responses in humans. The physiological studies in horses show many similarities to human responses with much evidence demonstrating that WT exercise is an aerobic form of exercise which does not appear to induce improvement in aerobic capacity when used within training programs. Equine and canine studies have shown that water depth can have a significant effect on the biomechanical responses to WT exercise, but little is known about the effect of different speeds at the various water depths. Key areas we would recommend for future research are as follows: how combinations of water depth and speed alter equine biomechanics compared to overland exercise, determination of long-term benefits of WT exercise, and how to use WT for rehabilitation for horses with specific injury.     

Dynamic respiratory endoscopy without treadmill in 68 performance Standardbred,Thoroughbred and saddle horses under natural training conditions

Reasons for performing study: High speed treadmill endoscopy provides a true assessment and diagnosis of the dynamic obstructions of the upper equine respiratory tract (DO‐URT). However, treadmills do not always allow reproduction of the exact conditions of dynamic collapse of the URT. The availability of on‐board endoscopes, which could be used without a treadmill, would make exercising endoscopy readily available to more equine practices. Objectives: To develop and validate an innovative endoscope which could be used for the examination of the URT at exercise in ridden and harnessed sport horses performing in natural conditions. Methods: Authors worked closely with engineers of a company manufacturing veterinary endoscopes. Over a 2‐year period several prototypes were tested on more than 20 cooperative horses performing either in trot, gallop, jumping or endurance. The final Dynamic Respiratory Scope (DRS) allows real‐time visualisation of the URT and video recordings for post test reviewing and archiving. The DRS was then tested in 2 equine livery yards. Performance horses presented for investigation of abnormal respiratory noises at exercise and/or poor performance were subjected to exercising endoscopy. Endoscopic images of the URT were recorded and video recordings of the URT were reviewed post test. Results: A total of 68 horses were examined: 39 harnessed Standardbred and 29 mounted horses (16 Thoroughbred and 13 saddle horses). Of these, 44 were diagnosed with a URT abnormality. Good quality videos were obtained even at maximum speed in all cases. The innovative insertion tube provided very stable images compared to those obtained with flexible video endoscopes on treadmills. Conclusions: This study validates the safety and the reliability of the DRS for imaging the equine URT during natural exercising conditions. Potential relevance: Most common causes of DO‐URT can be diagnosed easily during any type of performance without a treadmill and the DRS offers a great potential for further URT clinical research.     

A Pilot Study to Assess the Feasibility of a Submaximal Exercise Test to Measure Individual Response to Cardiac Medication in Dogs with Acquired Heart Failure

Exercise testing is not commonly used in canine medicine because of several limitations. The aim of this study was to investigate the suitability of a treadmill test to measure the exercise capacity of untrained canine cardiac patients and to measure some biological parameters that might reflect the tolerance of dogs with heart failure to submaximal exercise. The exercise capacity of seven dogs with naturally occurring heart failure was evaluated before the institution of cardiac medication and 7 days after the beginning of the study. An additional re-examination was requested after 28 days. The exercise test was performed on a motorized treadmill at three different speeds (0.5 m/s, 1.0 m/s and 1.5 m/s). The following parameters were measured at the end of each stage and after 20 min recovery: heart rate, rectal temperature, glucose, lactate, aspartate aminotransferase, creatine kinase, Pvo ₂, Pvco ₂, pH, haematocrit, bicarbonate, sodium, potassium and chloride. Serum cardiac troponin-I was also measured at the beginning of the test and at the end of the recovery period. Owners’ perception reflected the ability of their dogs to exercise on the treadmill. Lactate level increased noticeably with the intensity of the exercise test, and its variation coincided with different exercise tolerance observed by the owners. Heart rate seemed to follow a similar trend in the few dogs presented in sinus rhythm. None of the remaining parameters appeared to be sensitive indicators of activity level in the dogs used in this study. The treadmill exercise test in dogs with acquired heart failure is feasible and might provide useful information for assessing individual response to cardiac medication. Lactate and heart rate seemed to reflect individual levels of exercise tolerance, although further studies are necessary to confirm the reliability and repeatability of this test.     

Clinical evaluation of poor performance in the racehorse: the results of 275 evaluations

A clinical sports medicine evaluation was applied to 275 racehorses with a history of poor racing performance. The poor performance evaluation included a) general physical examination and basic laboratory screening; b) respiratory examination including auscultation, thoracic radiographs, ventilation-perfusion lung scintigraphy and upper airway endoscopy at rest and during maximal treadmill exercise c) examination of the musculoskeletal system including lameness examination, video gait analysis at high speed, post exercise serum chemistry to identify obvious as well as sub-clinical myopathies, high detail radiography and nuclear scintigraphy; d) cardiac examination including auscultation, electrocardiographic analysis during strenuous exercise and when indicated, echocardiography; and e) a standardised exercise stress test entailing the measurement of oxygen consumption, carbon dioxide production, venous blood lactate concentration and heart rate during sequentially increasing running speeds on the high speed treadmill. The choice of diagnostic methodologies utilised were tailored to each individual in order to determine most efficiently the abnormalities contributing to inadequate racing performance. The results of this clinical evaluation showed that 1) many of the diagnoses were subtle requiring the use of sophisticated diagnostic equipment including scintigraphy and dynamic evaluation of the horse exercising on the high speed treadmill and 2) 84 per cent of the horses were diagnosed as suffering from more than one problem leading to the supposition that inadequate athletic performance is often caused by a constellation of abnormalities requiring a comprehensive approach to diagnosing decreased athletic capability.     

Physiological responses of young thoroughbred horses to intermittent high-intensity treadmill training

Background

Training of young Thoroughbred horses must balance development of cardiopulmonary function and aerobic capacity with loading of the musculoskeletal system that can potentially cause structural damage and/or lameness. High-speed equine treadmills are sometimes used to supplement exercise on a track in the training of young Thoroughbreds because the horse can run at high speeds but without the added weight of a rider. We tested the hypothesis that intermittent high-intensity exercise on a treadmill of young Thoroughbred horses entering training can enhance development of aerobic capacity (Vo₂max) and running performance more than conventional training under saddle, and do so without causing lameness.

Results

Twelve yearling Thoroughbreds trained for 8 months with conventional riding (C) only, conventional riding plus a short (2 month, S) interval of once-per-week high-intensity treadmill exercise, or a long (8 month, L) interval of once-per-week high-intensity treadmill exercise. Three treadmill exercise tests evaluated Vo₂max, oxygen transport and running performance variables in June of the yearling year (only for L), October of the yearling year and April of the 2-year-old year. No horses experienced lameness during the study. Aerobic capacity increased in all groups after training. In both October and April, Vo₂max in L was higher than in C, but did not differ between L and S or S and C. Running speeds eliciting Vo₂max also increased in all groups after training, with S (809 ± 3 m/s) and L (804 ± 9 m/s) higher than C (764 ± 27 m/s). Maximum heart rate decreased for all groups after training. Hematocrit and hemoglobin concentration increased for L throughout training.

Conclusions

Young Thoroughbred horses can increase aerobic capacity and running performance more than by strictly using track training under saddle with the addition of intermittent high-intensity treadmill exercise, and they can do so without experiencing lameness. This finding suggests that young racehorses might be able to achieve higher aerobic fitness during training without subjecting their musculoskeletal systems to increased loading and risk of developing lameness. The findings of this preliminary study do not indicate a specific protocol to best achieve this goal.     

Treadmill exercise prevents diabetes-induced increases in lipid peroxidation and decreases in Cu,Zn-superoxide dismutase levels in the hippocampus of Zucker diabetic fatty rats

In the present study, we investigated the effects of treadmill exercise on lipid peroxidation and Cu,Zn-superoxide dismutase (SOD1) levels in the hippocampus of Zucker diabetic fatty (ZDF) rats and lean control rats (ZLC) during the onset of diabetes. At 7 weeks of age, ZLC and ZDF rats were either placed on a stationary treadmill or made to run for 1 h/day for 5 consecutive days at 16~22 m/min for 5 weeks. At 12 weeks of age, the ZDF rats had significantly higher blood glucose levels and body weight than the ZLC rats. In addition, malondialdehyde (MDA) levels in the hippocampus of the ZDF rats were significantly higher than those of the ZLC rats whereas SOD1 levels in the hippocampus of the ZDF rats were moderately decreased. Notably, treadmill exercise prevented the increase of blood glucose levels in ZDF rats. In addition, treadmill exercise significantly ameliorated changes in MDA and SOD1 levels in the hippocampus although SOD activity was not altered. These findings suggest that diabetes increases lipid peroxidation and decreases SOD1 levels, and treadmill exercise can mitigate diabetes-induced oxidative damage in the hippocampus.     

Effect of Treadmill Exercise and Hydrogen-rich Water Intake on Serum Oxidative and Anti-oxidative Metabolites in Serum of Thoroughbred Horses

The present study aimed to clarify changes of oxidative stress and antioxidative functions in treadmill-exercised Thoroughbred horses (n=5, 3 to 7 years old), using recently developed techniques for measurement of serum d-ROMs for oxidative stress, and BAP for antioxidative markers. Also, the effect of nasogastric administration of hydrogen-rich water (HW) or placebo water preceding the treadmill exercise on these parameters was examined. Each horse was subjected to a maximum level of treadmill exercise in which the horses were exhausted at an average speed of 13.2 ± 0.84 m/sec. Blood samples were taken 4 times, immediately before the intake of HW or placebo water at 30 min preceding the treadmill exercise, immediately before the exercise (pre-exercise), immediately after the exercise (post-exercise) and at 30 min following the exercise. In all horses, both d-ROMs and BAP values significantly increased at post-exercise. The increase in d-ROMs tended to be lower in the HW trial, as compared to the placebo trial at pre-exercise. The increase in BAP was considerable at approximately 150% of the pre-exercise values in both the HW and placebo treatment trials. The BAP/d-ROMs ratio was significantly elevated at post-exercise in both treatment trials, while a significant elevation was also observed at pre-exercise in the HW trial. BAP, d-ROM, and the BAP/d-ROM ratio tended to decline at 30 min after the exercise, except BAP and BAP/d-ROMs in the placebo trial. These results demonstrate that the marked elevation of oxidative stress and anitioxidative functions occurred simultaneously in the intensively exercised horses, and suggest a possibility that HW has some antioxidative efficacy.     

Use of successive dynamic videoendoscopic evaluations to identify progression of recurrent laryngeal neuropathy in three horses

CASE DESCRIPTION: 3 racehorses were evaluated because of poor performance or abnormal noise originating from the upper portion of the respiratory tract. CLINICAL FINDINGS: During maximal exercise, initial dynamic videoendoscopy of the upper respiratory tract revealed complete arytenoid cartilage abduction in 2 horses and incomplete but adequate abduction of the left arytenoid cartilage in 1 horse. Subsequent exercising endoscopic evaluation revealed severe dynamic collapse of the left arytenoid cartilage and vocal fold in all 3 horses. TREATMENT AND OUTCOME: 2 horses were treated with prosthetic left laryngoplasty and raced successfully. One horse was retired from racing. CLINICAL RELEVANCE: Idiopathic laryngeal hemiplegia can be a progressive disease. Successive dynamic videoendoscopic upper airway evaluations were used to confirm progression of left laryngeal hemiplegia in these 3 horses. Videoendoscopy of the upper respiratory tract during exercise should be considered as part of the clinical evaluation of horses with signs of upper respiratory tract dysfunction.     

Causes of poor performance of horses during training, racing, or showing: 348 cases (1992-1996)

OBJECTIVE: To determine results for horses undergoing a high-speed treadmill examination, including videoendoscopy of the pharynx and larynx before and during exercise, echocardiography before and after exercise, and electrocardiography before, during, and after exercise, because of poor performance. DESIGN: Retrospective study. ANIMALS: 348 horses. RESULTS: A definitive diagnosis was obtained for 256 (73.5%) horses. One hundred forty-eight horses had dynamic obstruction of the airway during exercise, 33 had clinically important cardiac arrhythmias alone, 22 had a combination of dynamic airway obstruction and clinically important cardiac arrhythmias, 19 had poor cardiac fractional shortening immediately after exercise, 10 had exertional rhabdomyolyis, 15 had clinically apparent lameness, and 9 had other disorders. Thirty-nine of the horses with dynamic obstruction of the airway during exercise had multiple airway abnormalities. Fifty-three horses also had subclinical myopathy CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that a complete evaluation, including a high-speed treadmill examination, should be conducted in horses with poor performance, regardless or whether horses do or do not have a history of abnormal respiratory noises and particularly if the horses have grade-II or -III left laryngeal hemiplegia.     

ACTH stimulation test for the determination of salivary cortisol and of cortisol responses as markers of the training status/fitness of warm-blooded sports horses

Previous work (Marc et al., 2000) suggested that plasma cortisol responses to treadmill exercise or ACTH injection are a reliable marker for performance evaluation in warmblood horses. For practical purposes blood sample collections and treadmill exercise tests are somewhat troublesome and time consuming. The goal of this study was thus to evaluate the use of saliva for cortisol determination (by direct EIA) as a marker for performance and to investigate the reliability and repeatability of plasma cortisol responses to a single i.v. injection of ACTH (50 micrograms or 250 micrograms). Furthermore, the effect of training horses for 8 weeks 3 times per week covering the same distance (increasing from 3.5 km during the first week to 8 km during the last week) either by trotting (approximately 240 m/min) or by cantering (375 m/min) was investigated. For this purpose initially ten four-year-old Hannovarian geldings, all reared in the same State stud, were used. Mean overall correlation between salivary cortisol and plasma cortisol concentrations was 0.64 when samples of various points of time were used. However, in spite of attempts to standardize saliva sample collection, correlation between salivary cortisol levels and plasma cortisol levels at distinct points of time in different tests were low and significant (r = 0.85, p < 0.02) only in one test. Thus, salivary cortisol measurements for diagnostic purposes are not reliable or useful. The repeatability of plasma cortisol responses to ACTH for untrained and trained horses were r = 0.86 and r = 0.8 respectively (p < or = 0.01 and p < or = 0.05 respectively). Training horses either by trotting or cantering did not affect the cortisol response either to treadmill exercise or to stimulation by ACTH. It is concluded that the relationship between salivary cortisol levels and plasma cortisol levels is not close enough to allow the use of salivary cortisol determination as marker of the training status/fitness of horses. The repeatability of the cortisol response to ACTH is similar to the cortisol response to treadmill exercise. Based on plasma cortisol responses to ACTH or treadmill exercise training horses by cantering at low speed is not superior to training by trotting for the fitness of horses.     

Field exercise testing for assessing fitness in French standardbred trotters

This review considers standardized exercise testing which is, routinely used for French Trotters in the field. Track testing provides a more limited range of measurements than treadmill testing, but has the advantage of being performed in the horse's natural environment. Various measurements such as heart rate during exercise and blood lactate concentration after exercise may be measured on the track and lead to the calculation of physiological variables such as V200 (velocity corresponding to a 200 bpm heart rate) and V4 (velocity corresponding to a 4 mmol/L blood lactate concentration). V4 is related to the onset of blood lactate accumulation and relates to the aerobic capacity of the horse, as horses with high values for V4 have higher aerobic capacities. Although V4 is calculated during submaximal intensity exercise, it is related to racing performance and seems to be the most important measurement to assess changes in fitness. V200 represents the cardiac capacity of the horse during exercise and is close to V4 in mature horses. To explain further the clinical usefulness of track testing, and to help interpret both V4 and V200 variables, examples of exercise tests in 3-year-old French Trotters are presented here. These results show that changes may occur in V4 and V200 according to different factors such as the horse's physical ability and either training or disease states. It underlines the importance of exercise tests for both trainers and veterinarians and how they may help in the evaluation of a horse's performance ability; in defining the intensity of a training program, and also in the early detection of underlying diseases.     

The effect of dietary protein level on exercising horses

Six mature Quarter Horse mares were used in a crossover design to assess the effect of dietary protein level on metabolic response to exercise. After a 2-wk adaptation period to either a 12.9% (control) or an 18.5% CP (high-protein) diet, each mare performed a standard exercise test. The test consisted of a 15-min exercise period at 4.5 m/sec on a 9% grade motorized treadmill. Exercise resulted in an increase in heart rate (P less than .001), but there was no difference (P less than .05) between dietary treatments. In the jugular vein, lactate increased (P less than .01) from 6.3 to 52.0 mg/100 ml in the control group and increased from 6.3 to 45.6 mg/100 ml in the high-protein group. There was an interaction (P less than .05) between diet and exercise for lactate. Plasma NH3 increased (P less than .001) during exercise, but not until the 15th min, at which time NH3 increased over fourfold in both groups. Dietary protein did not affect NH3; however, urea-N was higher (P less than .001) in horses receiving the high-protein diet. Plasma alanine increased from 13.6 to 30.3 mumol/100 ml and glutamine increased from 49.3 to 62.5 mumol/100 ml in the control group. In the high-protein group, alanine increased from 10.2 to 25.8 mumol/100 ml, whereas glutamine increased from 39.3 to 49.2 mumol/100 ml. Our study detected no metabolic evidence for a detrimental effect of excess dietary protein in horses exercising on a graded treadmill at 4.5 m/sec for 15 min.     

High-speed treadmill videoendoscopic examination of the upper respiratory tract in the horse: the results of 291 clinical cases

The purpose of the study was to describe the prevalence of upper airway abnormalities and establish if any significant associations existed between study variables and the two most frequently identified disorders; axial deviation of the aryepiglottic folds and dorsal displacement of the soft palate. The clinical records and video-recordings of all horses referred for upper respiratory tract evaluation during high-speed treadmill videoendoscopy between November 1997 and September 2003 were reviewed. Of 291 horses included in the study, 265 underwent resting endoscopy and 42% (112/265) had a recognised abnormality. More than one abnormality was identified in 49% of horses. In general, horses referred specifically for evaluation of a respiratory tract noise were more likely to have an abnormality detected during exercise than those referred for high-speed treadmill videoendoscopy for poor performance (82% versus 49%). Axial deviation of the aryepiglottic folds (105/192, 55%) was the most common abnormality identified, followed by dorsal displacement of the soft palate (74/192, 39%) and idiopathic left laryngeal hemiplegia (65/192, 34%). Other abnormalities identified included arytenoid collapse, vocal fold collapse, dynamic pharyngeal collapse, epiglottic fold entrapment, epiglottic retroversion, rostral displacement of the palatopharyngeal arch and right laryngeal hemiplegia. In horses with axial deviation of the aryepiglottic folds there was a significant association between the increasing severity of the deviation and the increasing number of abnormalities detected. There were no other associations found. High-speed treadmill videoendoscopy is an important component of the evaluation of poor performance, particularly in horses with a history of respiratory noise. The occurrence of multiple abnormalities in a large proportion of horses suggests that high-speed treadmill videoendoscopy should be recommended, where possible, to make an accurate diagnosis, advise on appropriate treatment options and provide a prognosis for affected horses.     

Comparison of tracheal aspirates before and after high-speed treadmill exercise in racehorses

OBJECTIVE: To determine whether percentages of neutrophils in tracheal aspirate (TA) samples collected from racehorses are increased after exercise and whether interpretation of results from TA samples taken before and after exercise agree. DESIGN: Case series of 40 young Thoroughbred and Standardbred racehorses in race training presented for evaluation of poor performance. PROCEDURE: TA samples were collected endoscopically from racehorses presented for poor performance 24 h before and 1 to 2 h after high speed treadmill exercise testing. Aliquots of the retrieved fluid were cytocentrifuged and smears were stained with Diff-Quik. Mean neutrophil counts were expressed as percentages of the total number of inflammatory cells counted and subsequently were categorised as either above or below an accepted cut-off of 20%. Comparisons between percentages of neutrophils before and after exercise were made. RESULTS: Percentage of neutrophils from TA samples obtained from racehorses after exercise was significantly higher than neutrophil percentages from TA samples collected from the same horse before exercise. In horses with TA specimens that were categorised as having < or = 20% neutrophils before treadmill exercise, the percentage of neutrophils in their TA specimens after exercise was, on average, significantly higher and was greater than the cut-off value of 20%. CONCLUSION: Recent strenuous exercise may change the proportion of neutrophils in lower airways of racehorses and practitioners should be aware of this when collecting and interpreting the results from TA samples. The most practical time for collection of a TA sample to obtain the most diagnostically useful information might be after a suitable washout period of at least 1 to 2 h post-exercise.     

Changes in equine metabolic characteristics due to exercise fatigue

Eight horses exercised to fatigue were used to characterize the resulting changes in blood pH, in blood lactate, free fatty acid, bicarbonate, and ammonia concentrations, and in muscle glycogen concentrations. The exercise test was conducted at a speed of 4.5 m/s on a motorized equine treadmill set at a 9% grade. At fatigue, all variables differed significantly (P less than 0.05) from base-line values. Heart rate averaged 191.1 +/- 6.5 beats/min at fatigue, and the plasma lactate concentrations increased from 7.8 +/- 0.95 mg/dl to 94.3 +/- 19.2 mg/dl. Ammonia concentrations increased from 66.7 +/- 6.9 mumol/L before exercise to 136.9 +/- 18.6 mumol/L at fatigue. Bicarbonate concentrations decreased from 31.3 +/- 0.4 mM to 21.1 +/- 1.8 mM, and pH decreased from 7.37 +/- 0.01 to 7.28 +/- 0.04. Free fatty acid concentrations were higher at fatigue and increased throughout the recovery period. Exercise resulted in a 25% decrease of muscle glycogen concentration in gluteus medius specimens.     

Hematological and Blood Gas Parameters' Response to Treadmill Exercise Test in Eventing Horses Fed Different Protein Levels

The aim of this study was to investigate the responses to exercise in athletic horses fed different protein levels. Twenty-four Brazilian Sport Horses (body weight [BW] between 432 and 560 kg and body condition score [BCS] 5.0–5.5) undergoing eventing training were used. The experiment was a randomized design with four treatments (diets) and two exercise tests. Diets were composed of 7.5%, 9.0%, 11.0%, and 13.0% crude protein. The exercise tests consisted of a warm-up and galloping from 6.0 m/s with speed increases every 1 minute until 10 m/s. Venous blood samples were collected at preprandial time, before, during, and after the exercise tests, and at the recovery time. Blood samples were analyzed for hematocrit, lactate, glucose, total plasma protein, serum aspartate aminotransferase, creatine kinase, lactate dehydrogenase, urea, uric acid, creatinine, serum Cl⁻, and venous blood gas. The results were analyzed using a split-plot design, and regression analyses were performed. There were no differences in BW and BCS. The protein levels did not affect the variables VL₂, VL_4, V₁₅₀, and V₂₀₀. Serum urea and uric acid concentrations were affected by protein diet levels. After the exercise tests, the blood pH, acid–base, and electrolyte balance of the horses were not affected by the protein of the diets. The protein diet levels did not affect the horses' performance variables. At the same time, high protein concentrations in the diet can alter the acid–base balance in athletic horses and should be used with caution.