Browsing by Author "Léguillette, Renaud"
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- ItemOpen AccessComparison of physiological demands in Warmblood show jumping horses over a standardized 1.10 m jumping course versus a standardized exercise test on a track(2020-06-08) Léguillette, Renaud; Bond, Stephanie L; Lawlor, Kelda; Haan, Tineke d; Weber, Lauren MAbstract Background A greater understanding of exercise physiology and biochemistry is required for the sport horse disciplines, including show jumping. Conditioning of horses for show jumping is empirical because they are primarily trained on flat ground, however the equivalent workload between jumping and flat work is currently unknown. The objectives of the study were therefore to compare the physiological demands of Warmblood show jumpers over a standardized 1.10 m course vs a 600 m standardized incremental exercise test on flat ground, and to report reference field test values for competitive show jumping horses. In this prospective field study, 21 healthy, actively competing Warmblood show jumping horses were assessed to determine physiological variables after a standardized jumping course at 6.4 m/s (average speed) and track standardized incremental exercise test at 5 m/s, 8 m/s and 11 m/s. Heart rate, velocity, blood lactate, blood pH, pCO2, bicarbonate, PCV and TP concentrations were recorded. V200, V170 and VLa4 were calculated. Parametric statistics were performed on analysis of all 21 horses’ variables. Results Contrary to exercise at 5 m/s and 11 m/s, cantering at 8 m/s did not induce any significant difference in blood lactate, mean heart rate or mean venous blood pH compared to after completion of the jumping course. Conclusions Jumping a 1.10 m course demands a statistically similar workload to cantering around a flat track at 8 m/s. This study will help to test fitness and design conditioning programs for Warmblood show jumping horses.
- ItemOpen AccessEffect of injected dexamethasone on relative cytokine mRNA expression in bronchoalveolar lavage fluid in horses with mild asthma(2019-11-06) Bond, Stephanie L; Hundt, Jana; Léguillette, RenaudAbstract Background Mild equine asthma is a common inflammatory airway disease of the horse. The primary treatment of mild equine asthma is corticosteroids. The purpose of this study was to investigate the effects of injected dexamethasone on relative IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p35, IL-17, IL-23, IFN-γ, Eotaxin-2 and TNF-α mRNA expression in bronchoalveolar lavage (BAL) fluid in healthy Thoroughbred horses (n = 6), and those with mild equine asthma (n = 7). Results Horses with mild equine asthma had a significantly greater bronchoalveolar lavage mast cell percentage than healthy horses both before and after treatment. Mild equine asthma was associated with a 4.95-fold up-regulation of IL-17 (p = 0.026) and a 2.54-fold down-regulation of IL-10 (p = 0.049) compared to healthy horses. TNF-α was down-regulated in response to dexamethasone treatment in both healthy horses (3.03-fold, p = 0.023) and those with mild equine asthma (1.75-fold, p = 0.023). IL-5 was also down-regulated in horses with mild asthma (2.17-fold, p = 0.048). Conclusions Horses with mild equine asthma have a lower concentration of IL-10 in BAL fluid than healthy controls which concurs with human asthmatics. The marked up-regulation of IL-17 in horses with mild asthma suggests these horses had a true tendency of “allergic” airway inflammation in response to environmental allergens. Dexamethasone administration exerted anti-inflammatory effects associated with down-regulation of TNF-α in all horses, and decreased levels of IL-5 mRNA expression in horses with mild equine asthma. The inhibition of the Th-2 response, without any alterations to the airway cytology, indicates that maintained exposure to environmental allergens perpetuates airway inflammation.
- ItemOpen AccessEquine lung inflammation in Alberta: evaluation of clinical signs, risk-screen questionnaire, and bronchoalveolar lavage in recurrent airway obstruction and inflammatory airway disease(2012) Wasko, Andrea Jayne; Léguillette, Renaud; Barkema, HermanNon-infectious equine respiratory diseases consist of recurrent airway obstruction (RAO) and inflammatory airway disease (IAD). Recurrent airway obstruction has similarities with human asthma, whereas horses with IAD have a milder airway inflammation and do not exhibit respiratory clinical signs at rest. This thesis presents a review on RAO and IAD, followed by a manuscript on the evaluation of a risk-screening questionnaire (RSQ) to detect equine lung inflammation measured by a bronchoalveolar lavage (BAL) in a large field study. The RSQ had a high sensitivity to detect severe lower airway inflammation and would be a good screening tool in practice. Furthermore, there was a high prevalence of moderate airway inflammation in this population, but the RSQ did not differentiate between moderate airway inflammation and normal horses. Finally feeding round hay bales was a risk factor for severe airway inflammation.
- ItemOpen AccessExercising horses on water treadmills: Understanding the workload, mechanics, and conditioning effects of water treadmill exercise.(2019-10-22) McCrae, Persephone; Léguillette, Renaud; Millet, Guillaume Y.; Edwards, William Brent; Rolian, CampbellDespite the growing popularity of equine water treadmills (WTs), there is very little scientific evidence to support their use in the conditioning or rehabilitation of sport horses. As a result, the success of WT use is in large part dependent on the ability of the operator to assess and create an appropriate plan. Therefore, the projects described in this thesis were established to assess the workload, conditioning effects, and limb kinetics and kinematics associated with equine WT exercise. The results gathered from these studies will allow more evidence-based use of equine WTs for training and rehabilitation. It was essential to first understand the effort required during WT exercise. We found that water height had a greater impact on workload than the speed of the treadmill belt. The greatest workload occurred with water at the height of the stifle, however this was still considered to be a relatively low-intensity exercise. Using our understanding of workload from the first study, the second study aimed to assess the conditioning effects of a WT exercise program. We assessed the fitness of horses before and after 18-days of WT training, including a dry control (exercised without water), using a maximal intensity exercise track test. Peak oxygen consumption, as tested on the racetrack, increased significantly in the experimental horses, indicating that despite the low workload on the WT, exercising horses in high water heights improves fitness. As the primary rationale for using WTs is to reduce concussive forces experienced by the limb, the third study evaluated the effect of water height and speed on segmental acceleration and impact attenuation during WT exercise. The unique properties of water, especially when water was used at a high level, resulted in reduced segmental accelerations and increased attenuation. These findings suggest that WT exercise may be beneficial in the rehabilitation of lower limb injuries in horses. Lastly, we examined 2-dimensional forelimb kinematics of horses on land and under various WT conditions before and after 8-days of WT conditioning. We found that water height alters limb kinematics and may be meaningful for physical rehabilitation. However, prolonged exposure to WT training does not have a lasting effect overground kinematics. Altogether, these studies have elucidated objective information that will serve as the foundation for the effective and safe use of WTs in the training and rehabilitation of performance horses.
- ItemOpen AccessField-training in young two-year-old thoroughbreds: investigating cardiorespiratory adaptations and the presence of exercise induced pulmonary hemorrhage(2024-04-26) Massie, Shannon; Bayly, Warwick; Ohmura, Hajime; Takahashi, Yuji; Mukai, Kazutaka; Léguillette, RenaudAbstract Background Comparatively little is known regarding the initial cardiorespiratory response of young racehorses to training. The objectives were to compare physiological parameters before and after introductory training and determine whether young Thoroughbreds show endoscopic signs of exercise-induced pulmonary hemorrhage (EIPH). Ten Thoroughbreds (20–23 months) underwent 12-weeks of introductory training, including weekly speed sessions. Two 600 m high-speed exercise tests (HSET) were performed following weeks 4 and 12 while wearing a validated ergospirometry facemask. Peak oxygen consumption (V̇O2pk) and ventilatory parameters (tidal volume, VT; peak inspiratory and expiratory flow, PkV̇I, PkV̇E; respiratory frequency, Rf; minute ventilation, V̇E) were measured. The ventilatory equivalent of oxygen (V̇E/V̇O2) and the aerobic and anaerobic contributions to energy production were calculated. Maximal heart rate (HRmax) and HR at maximal speed (HRVmax) were determined. Post-exercise hematocrit, plasma ammonia and blood lactate were measured. Evidence of EIPH was investigated via tracheobronchoscopy post-exercise. Results were compared (paired t-test, P < 0.05). Results Horses were faster following training (P < 0.001) and V̇O2pk increased 28 ml/(kg total mass.min) (28 ± 16%; P < 0.001). Ventilatory (V̇E, P = 0.0015; Rf, P < 0.001; PkV̇I, P < 0.001; PkV̇E, P < 0.001) and cardiovascular parameters (HRmax, P = 0.03; HRVmax, P = 0.04) increased. The increase in V̇E was due to greater Rf, but not VT. V̇E/V̇O2 was lower (26 ± 3.6 vs 23 ± 3.7; P = 0.02), indicating improved ventilatory efficiency. Anaerobic contribution to total energy production increased from 15.6 ± 6.1% to 18.5 ± 6.3% (P = 0.02). Post-exercise hematocrit (P < 0.001), plasma ammonia (P = 0.03) and blood lactate (P = 0.001) increased following training. Horses showed no signs of EIPH. Conclusions Young two-year-old Thoroughbreds responded well to introductory training without developing tracheobronchoscopic evidence of EIPH.
- ItemOpen AccessHigh intensity, short duration pulling in heavy horses: physiological effects of competition and rapid weight change(2017-11-07) Greco-Otto, Persephone; Massie, Shannon; Shields, Erin; Roy, Marie-France; Pajor, Edmond; Léguillette, RenaudAbstract Background The Heavy Horse Pull is a competition where teams of two horses pull an increasingly heavy sled for a short distance. Similar to human wrestlers, some horses may undergo rapid weight change in order to enter a lower weight category. The objectives were to study the physiological effects of this practice as well as of the pulling competition in draft horses. Results Fifty horses were divided into light-, middle- and heavyweight categories based on their arrival weights and competed 1–3 days after. Body weight was measured upon arrival and pre-competition. Blood was sampled for chemistry and high sensitivity cardiac troponin T (hscTnT) at arrival, pre- and post-competition in 34, 26 and 20 horses, respectively. Body weight increased significantly between arrival and pre-competition for light (7.2% (Median: 62.8Kg (41.7–77.0)) and middle (8.6% (Median: 80.5Kg (62.7–90.9)) weight categories. Change in body weight was correlated (r = 0.69, p = 0.002) with competition ranking for middleweights. The ratios of weight pulled to team body weight were 2.7 (1.9–2.8), 2.6 (2.5–2.6) and 2.4 (2.2–2.5) for the lightweights, middleweights and heavyweights, respectively. Blood chemistry indicated hemoconcentration on arrival in the middleweight and lightweight horses. Hemoconcentration was not seen on arrival in some horses with marked rapid weight change. Overall, no chemistry parameter changed between pre- and post-competition. The hscTnT stayed within normal range post-competition. Conclusions While horses arrived to the event with indications of hemoconcentration, they appeared to have sufficient time to rehydrate prior to competition, and the effects of the competition were reversible within 3 h.
- ItemOpen Access'High-sensitivity' Cardiac Troponin-T Assay Use in Horses: Analytical and Biological Validation, Post-Race Kinetics and Sampling Guidelines(2016) Shields, Erin; Léguillette, Renaud; Seiden-Long, Isolde; Scott, Mike; Caulkett, Nigel’High-sensitivity’ cardiac troponin assays are now the standard in human cardiology, but validation and exercise-kinetics in horses have not been investigated. Objectives: Appropriately validate the hscTnT assay for use in horses, establish reference intervals, determine biological variation, explore race-induced hscTnT release kinetics, provide clinical sampling guidelines, and create model for sub-clinical cardiomyopathy. Methods/Results: Analytical performance of the assay in horses is verified. Reference intervals: upper 95th and 99th percentile of the hscTnT population distribution were 6.8 and 16.2ng/L in Non-Competition Horses, and 14.0 and 23.2ng/L in Racing-Thoroughbreds. Biological variation not appreciated due to number of horses below assay detection level. Racing-exercise caused peak hscTnT levels at 2-6h post-race, may approach 99th percentile URL, but declined by 12-24h. Clinician guidelines: normal horses should have declining levels by 12-24h and single values during this time-period should be <99th percentile URL:23.2ng/L. Occult sodium monensin cardiomyopathy model induced hscTnT elevations and ultrastructural cardiac changes.
- ItemOpen AccessMild Equine Asthma: Effects of Commonly Used Treatments on the Respiratory Microbiota, Inflammatory Gene Expression, and Aerobic Performance during High-Intensity Exercise(2019-04-29) Bond, Stephanie Laura; Léguillette, Renaud; Scott, W. Michael; Bayly, Warwick M.; Easton, Paul A.Mild equine asthma (MEA) is an inflammatory airway disease of the horse which affects a large proportion of the equine population. The pathogenesis of MEA is not fully elucidated, however, it is widely assumed to be a multifactorial disease, with expression of clinical signs largely influenced by environment. There is very little information available on the effects of treatment, which is typically focused on reducing airway inflammation through corticosteroid administration. Investigations into the equine respiratory environment in states of health and MEA were performed using: i) High-throughput sequencing techniques (16S and ITS2) to report the respiratory microbiota and mycobiota respectively, and ii) changes in relative inflammatory mRNA cytokine expression in bronchoalveolar lavage fluid (BALF). Changes in expression of inflammatory cytokine mRNA, equine herpesvirus (EHV)-1,2,4,5 glycoprotein B gene expression and changes in respiratory bacterial and fungal communities following dexamethasone treatment of healthy horses and those with MEA are explored. A portable equine ergospirometry system was used to determine the efficacy of treatment designed to reduce lung inflammation on aerobic (V̇O2peak) and anaerobic performance in horses with MEA. There were clear differences between the lower respiratory tract environment in healthy horses versus MEA. There was a clear separation in both the microbiota - Streptococcus was increased in horses with MEA – and relative inflammatory cytokine expression. Horses with MEA had a lower concentration of IL-10 in BALF than healthy controls, consistent with human asthmatics. There was significant up-regulation of IL-17 in horses with MEA, suggesting these horses exhibit “allergic” airway inflammation in response to environmental antigens. The single most important factor in the prevention and treatment of MEA appears to be environmental improvement, manifest by reduced inhaled particulate matter. Treatment with injected dexamethasone in horses with MEA was associated with down-regulation of IL-5, indicating a shift away from a dysregulated Th-2 response. Treatment with dexamethasone significantly affected the microbiota diversity, but not the mycobiota, which was overwhelmed by the effect of a sustained dusty environment. There is strong evidence that without environmental modifications, corticosteroid therapy alone fails to normalize airway neutrophilia. Treatment significantly increased V̇O2peak by an average 11.7% (saline) to 14.6% (dexamethasone).
- ItemOpen AccessPartitioning of pulmonary lung resistance in horses: Ex-vivo.(2013-01-28) Nicol, James Alexander; Léguillette, RenaudHorses can be affected by two non-infectious inflammatory lung diseases, namely heaves and inflammatory airway disease (IAD). Heaves is characterized by episodes of bronchoconstriction and has many similarities with asthma. It is challenging to treat, but before new therapies can be proposed it is necessary to understand which airway size is most affected by bronchoconstriction and is the best target for a new treatment. The aim of the present study is to dissect the lung resistance to airflow so that the “bottleneck” between lower airways of various sizes can be identified. The specific objectives were 1) to partition total lobar resistance (from the cranial lobes of horses’ lungs) using ex-vivo lungs ventilated in physiological conditions and 2) to assess the effect of increasing respiratory rate and negative chest pressure on lung mechanics at the level of different airway sizes. To do this, we used 13 healthy ex-vivo horse lungs and ventilated them in an airtight negative pressure box under 9 different conditions of pressure and respiratory rates, while partitioning of resistances were performed using the alveolar capsule and retrograde catheter techniques. Total lobar resistance (RL) partitioned into 4 component resistances: Large airway resistances (Rlarge), middle airway resistances (Rmiddle), small airway resistances (Rsmall), and resistances contributed by the lung tissue (Rtissue). We found that Rsmall was the airway size contributing the most resistance to RL, and that the relative contributions of Rlarge and Rsmall to RL increased when box pressure decreases. The relative contribution of Rtissue to RL did the opposite.
- ItemOpen AccessSwimming exercise in horses: cardiac and kinematics assessment(2022-05) Santosuosso, Emma; Léguillette, Renaud; Rolian, Campbell P.; Romero, Alfredo E.The great popularity of aquatic exercise among equestrian world and equine veterinarians have led the scientific community to study different types of aquatic exercise including swimming. Most of swimming publications were focused on cardiorespiratory physiology. However, the knowledge gap is still great. In cardiology, the limitations are basically due to difficulties to get a proper ECG in underwater conditions. In kinematics field, basic data are lacking as the swimming stride cycle has not been described yet. However, both cardiology and kinematics understanding are crucial to include swimming exercise in rehabilitation or conditioning programs. The knowledge should ensure safety of the exercise and potential benefits on the cardiac and orthopedics systems. Therefore, the projects described in this thesis aimed at describing some aspects of the cardiac physiology and kinematics during swimming. Two kinematics studies (chapters two and three) were focused on underwater fore- and hindlimbs motion. In both cases data obtained were compared to a reference (passive mobilization by handlers on the ground). The carpus showed the greatest ROM and angular velocity in the forelimbs. In the hindlimbs, stifle and tarsus had the greatest angular velocity. We found that tarsus ROM was similar during swimming and passive mobilization but fore/ hind fetlock, carpus and stifle ROMs were significantly greater during passive mobilization compared to swimming. For all joints, the angular velocity was greater during the retraction phase. A low ROM of front- and hindlimb fetlock during swimming could be beneficial for rehabilitation of suspensory apparatus and superficial digital flexor tendon. Swimming exercise could be beneficial for rehabilitation when greater ROM than those obtained in the water-treadmill with limited joint loading is desirable. The arrythmia chapter (chapter four) aimed at determining the frequency of cardiac arrhythmias during repetitive swimming exercise. We found that the overall frequency remained low. In conclusion, we showed for the first time that swimming is safe with a low frequency of arrhythmias and pathological arrhythmias in particular. Kinematics reveal a great potential for rehabilitation use with many possible applications in injured horses. Whereas the present studies were done on healthy horses, future studies should determine the benefits of swimming for rehabilitation.
- ItemOpen AccessTackling the Challenges of an Equine Metabolic Mask: Validating a Computational Approach to Simulate Airflow Using 3D Printed Models(2015-09-24) Massie, Shannon; Léguillette, RenaudMaximal aerobic capacity (VO2max) is considered the reference for determining an individual’s level of fitness. To measure VO2max, a subject must perform an incremental fitness test while wearing a facemask that samples expired gases and ventilation rates. In horses, the practicality of VO2max testing in the field is limited by mask design, specifically due to impedance of airflow. The trajectory of airflow as it enters and exits the nasal passage must therefore be fully understood in order to build a functional mask. Computational fluid dynamics (CFD) was used to model flow patterns and pressure changes at various rates in the equine nasal passage. Results were validated with experimental data obtained from a 3D printed model of a horse head. Preliminary mask designs were investigated using CFD and a current design was tested using the 3D printed model. Data was also collected on sport horses in the field.
- ItemOpen AccessTopography of the respiratory tract bacterial microbiota in cattle(2020-06-10) McMullen, Christopher; Alexander, Trevor W; Léguillette, Renaud; Workentine, Matthew; Timsit, EdouardAbstract Background Bacterial bronchopneumonia (BP) is the leading cause of morbidity and mortality in cattle. The nasopharynx is generally accepted as the primary source of pathogenic bacteria that cause BP. However, it has recently been shown in humans that the oropharynx may act as the primary reservoir for pathogens that reach the lung. The objective was therefore to describe the bacterial microbiota present along the entire cattle respiratory tract to determine which upper respiratory tract (URT) niches may contribute the most to the composition of the lung microbiota. Methods Seventeen upper and lower respiratory tract locations were sampled from 15 healthy feedlot steer calves. Samples were collected using a combination of swabs, protected specimen brushes, and saline washes. DNA was extracted from each sample and the 16S rRNA gene (V3-V4) was sequenced. Community composition, alpha-diversity, and beta-diversity were compared among sampling locations. Results Microbiota composition differed across sampling locations, with physiologically and anatomically distinct locations showing different relative abundances of 1137 observed sequence variants (SVs). An analysis of similarities showed that the lung was more similar to the nasopharynx (R-statistic = 0.091) than it was to the oropharynx (R-statistic = 0.709) or any other URT sampling location. Five distinct metacommunities were identified across all samples after clustering at the genus level using Dirichlet multinomial mixtures. This included a metacommunity found primarily in the lung and nasopharynx that was dominated by Mycoplasma. Further clustering at the SV level showed a shared metacommunity between the lung and nasopharynx that was dominated by Mycoplasma dispar. Other metacommunities found in the nostrils, tonsils, and oral microbiotas were dominated by Moraxella, Fusobacterium, and Streptococcus, respectively. Conclusions The nasopharyngeal bacterial microbiota is most similar to the lung bacterial microbiota in healthy cattle and therefore may serve as the primary source of bacteria to the lung. This finding indicates that the nasopharynx is likely the most important location that should be targeted when doing bovine respiratory microbiota research. Video abstract.
- ItemOpen AccessUpper and lower respiratory tract microbiota in horses: bacterial communities associated with health and mild asthma (inflammatory airway disease) and effects of dexamethasone(2017-08-23) Bond, Stephanie L; Timsit, Edouard; Workentine, Matthew; Alexander, Trevor; Léguillette, RenaudAbstract Background The microbial composition of the equine respiratory tract, and differences due to mild equine asthma (also called Inflammatory Airway Disease (IAD)) have not been reported. The primary treatment for control of IAD in horses are corticosteroids. The objectives were to characterize the upper and lower respiratory tract microbiota associated with respiratory health and IAD, and to investigate the effects of dexamethasone on these bacterial communities using high throughput sequencing. Results The respiratory microbiota of horses was dominated by four major phyla, Proteobacteria (43.85%), Actinobacteria (21.63%), Firmicutes (16.82%), and Bacteroidetes (13.24%). Fifty genera had a relative abundance > 0.1%, with Sphingomonas and Pantoea being the most abundant. The upper and lower respiratory tract microbiota differed in healthy horses, with a decrease in richness in the lower airways, and 2 OTUs that differed in abundance. There was a separation between bacterial communities in the lower respiratory tract of healthy and IAD horses; 6 OTUs in the tracheal community had different abundance with disease status, with Streptococcus being increased in IAD horses. Treatment with dexamethasone had an effect on the lower respiratory tract microbiota of both heathy and IAD horses, with 8 OTUs increasing in abundance (including Streptococcus) and 1 OTU decreasing. Conclusions The lower respiratory tract microbiota differed between healthy and IAD horses. Further research on the role of Streptococcus in IAD is warranted. Dexamethasone treatment affected the lower respiratory tract microbiota, which suggests that control of bacterial overgrowth in IAD horses treated with dexamethasone could be part of the treatment strategy.
- ItemOpen AccessWater treadmill exercise reduces equine limb segmental accelerations and increases shock attenuation(2019-09-13) Greco-Otto, Persephone; Baggaley, Michael; Edwards, W. B; Léguillette, RenaudAbstract Background Equine water treadmills (WTs) are growing in popularity because they are believed to allow for high resistance, low impact exercise. However, little is known about the effect of water height on limb loading. The aim of this study was to evaluate the effect of water height and speed on segmental acceleration and impact attenuation during WT exercise in horses. Three uniaxial accelerometers (sampling rate: 2500 Hz) were secured on the left forelimb (hoof, mid-cannon, mid-radius). Horses walked at two speeds (S1: 0.83 m/s, S2: 1.39 m/s) and three water heights (mid-cannon, carpus, stifle), with a dry WT control. Peak acceleration of each segment was averaged over five strides, attenuation was calculated, and stride frequency was estimated by the time between successive hoof contacts. Linear mixed effects models were used to examine the effects of water height, speed, and accelerometer location on peak acceleration, attenuation and stride frequency (p < 0.05). Results Peak acceleration at all locations was lower with water of any height compared to the dry control (p < 0.0001). Acceleration was reduced with water at the height of the stifle compared to mid-cannon water height (p = 0.02). Water at the height of the stifle attenuated more impact than water at the height of the cannon (p = 0.0001). Conclusions Water immersion during treadmill exercise reduced segmental accelerations and increased attenuation in horses. WT exercise may be beneficial in the rehabilitation of lower limb injuries in horses.
- ItemOpen AccessWorkload of horses on a water treadmill: effect of speed and water height on oxygen consumption and cardiorespiratory parameters(2017-11-28) Greco-Otto, Persephone; Bond, Stephanie; Sides, Raymond; Kwong, Grace P S; Bayly, Warwick; Léguillette, RenaudAbstract Background Despite the use of water treadmills (WT) in conditioning horses, the intensity of WT exercise has not been well documented. The workload on a WT is a function of water height and treadmill speed. Therefore, the purpose of this study was to determine the effects of these factors on workload during WT exercise. Fifteen client-owned Quarter Horses were used in a randomized, controlled study. Three belt speeds and three water heights (mid cannon, carpus and stifle), along with the control condition (dry treadmill, all three speeds), were tested. Measured outcomes were oxygen consumption (V̇O2), ventilation (respiratory frequency, tidal volume (VT)), heart rate (HR), and blood lactate. An ergospirometry system was used to measure V̇O2 and ventilation. Linear mixed effects models were used to examine the effects of presence or absence of water, water height and speed (as fixed effects) on measured outcomes. Results Water height and its interaction with speed had a significant effect on V̇O2, VT and HR, all peaking at the highest water level and speed (stifle at 1.39 m/s, median V̇O2 = 16.70 ml/(kg.min), VT = 6 L, HR = 69 bpm). Respiratory frequency peaked with water at the carpus at 1.39 m/s (median 49 breaths/min). For a given water height, the small increments in speed did not affect the measured outcomes. Post-exercise blood lactate concentration did not change. Conclusions Varying water height and speed affects the workload associated with WT exercise. The conditions utilized in this study were associated with low intensity exercise. Water height had a greater impact on exercise intensity than speed.