Dirt Track Surface Preparation and Associated Differences in Speed, Stride Length, and Stride Frequency in Galloping Horses.

In racehorses, the risk of musculoskeletal injury is linked to a decrease in speed and stride length (SL) over consecutive races prior to injury. Surface characteristics influence stride parameters. We hypothesized that large changes in stride parameters are found during galloping in response to dirt racetrack preparation. Harrowing of the back stretch of a half-mile dirt racetrack was altered in three individual lanes with decreasing depth from the inside to the outside. Track underlay compaction and water content were changed between days. Twelve horses (six on day 2) were sequentially galloped at a target speed of 16 ms-1 across the three lanes. Speed, stride frequency (SF), and SL were quantified with a GPS/GNSS logger. Mixed linear models with speed as covariate analyzed SF and SL, with track hardness and moisture content as fixed factors (p < 0.05). At the average speed of 16.48 ms-1, hardness (both p < 0.001) and moisture content (both p < 0.001) had significant effects on SF and SL. The largest difference in SL of 0.186 m between hardness and moisture conditions exceeded the 0.10 m longitudinal decrease over consecutive race starts previously identified as injury predictor. This suggests that detailed measurements of track conditions might be useful for refining injury prediction models.

Field-training in young two-year-old thoroughbreds: investigating cardiorespiratory adaptations and the presence of exercise induced pulmonary hemorrhage.

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.

Prevalence and severity of exercise-induced pulmonary hemorrhage in 2-year-old Thoroughbred racehorses and its relationship to performance.

BACKGROUND: Little has been reported regarding the prevalence and severity of exercise-induced pulmonary hemorrhage (EIPH) in 2-year-old Thoroughbred racehorses. OBJECTIVES: Evaluate EIPH prevalence and severity and its association with performance, speed index, furosemide administration, race distance, and track surface. ANIMALS: A total of 830 2-year-old Thoroughbreds. METHODS: Prospective blinded observational study. Videoendoscopy was performed 30 to 60 minutes postrace at 15 American racetracks. Three blinded observers independently assigned an EIPH grade (0-4) to each video, and prevalence and severity of EIPH were determined. Relationships of EIPH grade to performance, speed index, race distance, track surface, and prerace administration of furosemide were evaluated using Pearson's chi-squared test for categorical variables and analysis of variance (ANOVA) for numerical variables. Multivariable logistic regression assessed relationships between EIPH prevalence and severity, respectively, and the aforementioned independent variables. A P < .05 was considered significant. RESULTS: A total of 1071 tracheoendoscopies were recorded. The EIPH prevalence was 74% and for EIPH grade ≥3 was 8%. Speed index (P = .02) and finishing place (P = .004) were lower with EIPH ≥3. The EIPH prevalence and severity were lower at 2 tracks where postrace tracheoendoscopy was mandatory rather than voluntary (P < .001). Probability of observing EIPH was negatively associated with speed index (P = .01) at tracks where postrace tracheoendoscopy was mandatory. Prerace furosemide administration decreased the probability of EIPH occurrence (P = .007) and severity (P = .01) where study participation was voluntary. CONCLUSIONS AND CLINICAL IMPORTANCE: Prevalence and severity of EIPH in 2-year-old racehorses were consistent with that of older racehorses. An EIPH grade ≥3 was associated with decreased performance. Prerace furosemide administration was associated with a decreased likelihood, but not severity, of EIPH at most tracks.

A CONSORT-guided, randomized controlled clinical trial of nebulized administration of dexamethasone and saline on lower airway cytokine mRNA expression in horses with moderate asthma.

BACKGROUND: Nebulized administration of dexamethasone on cytokine regulation in horses with moderate asthma has not been investigated. OBJECTIVE: To investigate the changes in expression of inflammatory cytokine mRNA after nebulized administration of dexamethasone treatment of horses with moderate asthma. ANIMALS: Horses with naturally occurring moderate asthma (n = 16) and healthy control horses (n = 4). All horses were kept in a dusty environment during the study. METHODS: Prospective, parallel, randomized, controlled, blinded clinical trial. Blood endogenous cortisol, tracheal mucus, and bronchoalveolar lavage (BAL) were sampled before and after 13 days treatment with either nebulized administration of dexamethasone (15 mg once daily) or 0.9% saline (3 mL). Treatment groups were randomly allocated via randomization function (Microsoft Excel). Amplification of target mRNA in BAL fluid (IL-1ß, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IL-17, IL-23, IFN-γ, Eotaxin-2, and TNF-α) was achieved by qPCR, and the relative expression software tool was used to analyze BAL inflammatory cytokine mRNA. RESULTS: Horses treated with nebulized administration of dexamethasone had increased relative expression of IL-5 (1.70-fold), IL-6 (1.71-fold), IL-17 (3.25-fold), IL-12 (1.66-fold), and TNF-α (1.94-fold), and decreased relative expression of IL-23 (1.76-fold; P = .04) in samples collected on Day 14, in comparison to samples collected on Day 0 (all P < .05). Horses treated with nebulized administration of saline had no significant difference in the relative expression of any gene (all P > .05). CONCLUSIONS AND CLINICAL IMPORTANCE: Nebulized administration of dexamethasone was associated with increased expression of inflammatory cytokine mRNA. There was no improvement in inflammatory airway cytology associated with either dexamethasone or saline treatment.

Topography of the respiratory, oral, and guttural pouch bacterial and fungal microbiotas in horses.

BACKGROUND: The lower respiratory tract microbiota of the horse is different in states of health and disease, but the bacterial and fungal composition of the healthy respiratory tract of the horse has not been studied in detail. HYPOTHESIS: The respiratory tract environment contains distinct niche microbiotas, which decrease in species richness at more distal sampling locations. OBJECTIVE: Characterize the bacterial and fungal microbiotas along the upper and lower respiratory tract of the horse. ANIMALS: Healthy Argentinian Thoroughbred horses (n = 11) from the same client-owned herd. METHODS: Prospective cross-sectional study. Eleven upper and lower respiratory tract anatomical locations (bilateral nasal, bilateral deep nasal, nasopharynx, floor of mouth, oropharynx, arytenoids, proximal and distal trachea, guttural pouch) were sampled using a combination of swabs, protected specimen brushes, and saline washes. Total DNA was extracted from each sample and negative control, and the 16S rRNA gene (V4) and ITS2 region were sequenced. Community composition, alpha-diversity, and beta-diversity were compared among sampling locations. RESULTS: Fungal species richness and diversity were highest in the nostrils. More spatial heterogeneity was found in bacterial composition than in fungal communities. The pharyngeal microbiota was most similar to the distal tracheal bacterial and fungal microbiota in healthy horses and therefore may serve as the primary source of bacteria and fungi to the lower respiratory tract. CONCLUSIONS AND CLINICAL IMPORTANCE: The pharynx is an important location that should be targeted in respiratory microbiota research in horses. Future studies that investigate whether biomarkers of respiratory disease can be reliably detected in nasopharyngeal swab samples are warranted.

Frequency of cardiac arrhythmias in horses during straight and untethered swimming.

BACKGROUND: Cardiac arrhythmias have not been previously reported in horses while swimming. OBJECTIVES: To describe the type and frequency of encountered arrhythmias during repetitive swimming cycles. STUDY DESIGN: Descriptive observational study. METHODS: Sixteen horses swam five pool lengths (75 m), each separated by an active recovery walk. Continuous electrocardiograms (ECGs) were recorded (n = 80) and analysed during the pre-swim, swim and active-recovery periods. Arrhythmias were categorised as sinus arrhythmia (SA), sinus block, sinus pause (compensatory and non-compensatory), second degree atrioventricular block (2AVB) for physiological arrhythmias, supraventricular premature depolarisation (SVPD) and ventricular premature depolarisation (VPD) for non-physiological arrhythmias. A linear mixed-effects model was used to examine the effects of repetitive swim lengths on arrhythmias and swimming parameters. Data were reported as median [interquartile range]. RESULTS: Fifteen horses (94%) experienced at least one arrhythmia; however, the frequency remained low and 2AVB were only observed during the pre-swim period. The swimming heart rate (HR) was 162 bpm [141;173]. Sinus blocks, sinus pauses, SA, SVPD and VPD were all recorded at least once during swimming. Except for one VPD couplet, all premature depolarisations were isolated. During active-recovery, the HR was 105 bpm [103;106], with SA observed in 13 horses (81%), isolated SVPD in six horses (38%), sinus pause in one horse (6%) but no VPD present. MAIN LIMITATIONS: Limited number of horses precluding population prevalence assessment. CONCLUSION AND CLINICAL IMPORTANCE: High-quality underwater ECGs were acquired in swimming horses for the first time. The frequency of arrhythmias remained low and rare pathological arrhythmias were observed during repetitive swimming and active-recovery cycles. Swimming with active-recovery periods is not a high-risk cardio-arrhythmic exercise.

HISTORIAL: Arritmias cardiacas no han sido previamente descritas en caballos nadando. OBJETIVOS: Describir el tipo y frecuencia de arritmias encontradas durante ciclos de natación repetitivos. DISEÑO DEL ESTUDIO: Estudio descriptivo observacional. MÉTODOS: Diez y seis caballos nadaron cinco largos de piscina (75 m), cada uno separado por una caminata de recuperación. Electrocardiogramas continuos (ECGs) fueron grabados (n = 80) y analizados durante el pre-natación, natación y periodos de recuperación activa. Las arritmias fueron categorizadas en arritmia sinusal (SA), bloqueo sinusal, pausa sinusal (compensatoria y no compensatoria), bloqueo atrio ventricular de segundo grado (2AVB) para las arritmias fisiológicas, y en despolarización supraventricular prematura (SVPD) y despolarización ventricular prematura (VPD) para las arritmias no fisiológicas. Se utilizo un modelo linear de efecto mixto para examinar los efectos de nadar largos de piscina en forma repetitiva sobre las arritmias y parámetros de natación. Los datos fueron reportados como mediana [rango intercuartil]. RESULTADOS: Quince caballos (94%) sufrieron de al menos una arritmia, sin embargo la frecuencia permaneció baja. 2AVB fueron observados solo durante el periodo de pre-natación. La frecuencia cardiaca durante la natación (HR) fue de 162 bpm [141;173]. Bloqueos sinusales, pausas sinusales, SA, SVPD y VPD fueron todos registrados por lo menos una vez durante la natación. Excepto por un par de VPD, todas las despolarizaciones fueron aisladas. Durante la recuperación activa, la HR fue de 105 bpm [103;106], con SA observado en 13 caballos (81%), SVPD aislados en 6 caballos (38%), pausa sinusal en 1 caballos (6%) pero ningún VPD presente. LIMITACIONES PRINCIPALES: Número limitado de caballos lo que imposibilita hacer un asesoramiento de la prevalencia en la población. CONCLUSIÓN E IMPORTANCIA CLÍNICA: Por primera vez, se adquirieron ECGs debajo del agua de alta calidad en caballos nadando. La frecuencia de las arritmias permaneció baja y se observaron arritmias patológicas raramente durante la natación repetitiva y los ciclos de recuperación activa. Nadar con periodos de recuperación activa no es un ejercicio de alto riesgo cardio-arrítmico.

Free Swimming and Exercise-Induced Pulmonary Hemorrhage in Endurance Horses: A Preliminary Study.

Swimming is used for rehabilitation of musculoskeletal injuries and for conditioning to improve equine fitness. However, there are anecdotal reports that suggest that tethered swimming can induce epistaxis, likely secondary to exercise-induced pulmonary hemorrhage (EIPH). The objective of this observational, prospective study was to investigate if EIPH occurs during intensive free-swimming training sessions (5 × 70m) using 15 endurance horses. On tracheo-bronchoscopic evaluations following swimming, low grade mucus scores were observed, but no tracheal blood was observed. Bronchoalveolar lavage fluid analysis revealed a low cellularity, and the median red blood cell count (RBCs) was 271 cells/µL (interquartile range 150-363 cells/µL), which is much lower than the threshold of RBCs >1,000 cells/µL for horses to be considered positive for EIPH. Therefore, free swimming does not seem to predispose endurance horses to EIPH following a typical free-swimming training session.

Stride frequency derived from GPS speed fluctuations in galloping horses.

Changes in gallop stride parameters prior to injury have been documented previously in Thoroughbred racehorses. Validating solutions for quantification of fundamental stride parameters is important for large scale studies investigating injury related factors. This study describes a fast Fourier transformation-based method for extracting stride frequency (SF) values from speed fluctuations recorded with a standalone GPS-logger suitable for galloping horses. Limits of agreement with SF values derived from inertial measurement unit (IMU) pitch data are presented. Twelve Thoroughbred horses were instrumented with a GPS-logger (Vbox sport, Racelogic, 10 Hz samplerate) and a IMU-logger (Xsens DOT, Xsens, 120 Hz samplerate), both attached to the saddlecloth in the midline caudal to the saddle and time synchronized by minimizing root mean square error between differentiated GPS and IMU heading. Each horse performed three gallop trials with a target speed of 36miles per hour (16.1 ms-1) on a dirt racetrack. Average speed was 16.48 ms-1 ranging from 16.1 to 17.4 ms-1 between horses. Limits of agreement between GPS- and IMU-derived SF had a bias of 0.0032 Hz and a sample-by-sample precision of +/-0.027 Hz calculated over N = 2196 values. The stride length uncertainty related to the trial-by-trial SF precision of 0.0091 Hz achieved across 100 m gallop sections is smaller than the 10 cm decrease in stride length that has been associated with an increased risk of musculoskeletal injury. This suggests that the described method is suitable for calculating fundamental stride parameters in the context of injury prevention in galloping horses.

Kinematic Analysis During Straight Line Free Swimming in Horses: Part 1 - Forelimbs.

Background: Swimming is used for rehabilitation and conditioning purposes in equine sports medicine despite the lack of understanding of equine swimming kinematics. The aim of this study was to assess forelimb joints kinematics (elbow, carpus, and fetlock) in swimming horses. The specific objectives were 1- to calculate and compare joint angles in swimming vs. passive mobilizations (PM), 2- to determine joint angular velocities during a swimming stride cycle. Methods: Eleven elite endurance horses swam in a 100-m straight pool. Underwater (swimming) and overground (PM) videos were recorded from the horses' left side. Joint markers were applied on the lateral hoof wall, lateral metacarpal epicondyle, ulnar carpal bone, lateral humeral epicondyle, and the greater tubercle of humerus, from which elbow, carpus and fetlock angles, and angular velocities were obtained. As a reference, maximal fetlock, carpus, and elbow flexion/extension angles were determined during PM overground. Differences between angle extrema, angular velocities and range of motion (ROM) were compared. Results: Carpus and fetlock ROM were significantly smaller (p < 0.001) during swimming when compared with PM, while there was no difference in elbow ROM between both situations. The carpus had the greatest ROM of all joints during swimming. Absolute angular velocities values of all joints during swimming were greater during retraction than protraction (p < 0.001). When compared to other joints during protraction, the carpus joint reached the highest angular velocity. Conclusion: Swimming, as a rehabilitation exercise, has the potential to benefit horses where great elbow ROM with a moderate carpus and fetlock extension are wanted.

Kinematic Analysis During Straight Line Free Swimming in Horses: Part 2 - Hindlimbs.

BACKGROUND: Swimming is used for rehabilitation and conditioning purposes in equine sports medicine. We described the swimming kinematics of the equine forelimbs in Part 1. The aim of Part 2 is to assess stifle, tarsus, and hind fetlock joints kinematics in swimming horses. The objectives were 1- to calculate and compare joint angles during swimming against passive mobilizations (PM), 2- to determine joints angular velocities during a swimming stride cycle. METHODS: Eleven elite endurance horses were used to swim in a 100-meter straight pool. Underwater (swimming) and overground PM videos were recorded from the horses' left side. Joint markers were applied on the lateral hoof wall, lateral metatarsal epicondyle, lateral aspect of the talus, lateral femoral epicondyle, and great trochanter of the femur. As a reference, maximal fetlock, tarsus, and stifle flexion/extension angles were determined during PM overground. Differences between angle extrema, angular velocities, and range of motion (ROM) were statistically compared. RESULTS: The tarsus ROM was similar during PM and swimming. The stifle and fetlock ROM were greater during PM, although the stifle flexion was greater during swimming. The stifle and tarsus had the greatest hindlimb angular velocity during the swimming cycle. Greater angular velocities were observed during the retraction phase for all the hindlimb joints. CONCLUSION: A short retraction phase with great angular velocity for the joints of interest characterized the swimming pattern observed. Swimming may be beneficial in horses when an increased ROM of the tarsus and stifle or a reduced fetlock extension is indicated for rehabilitation purposes.

Validation of a Rapid Bronchoalveolar Lavage Fluid Colorimetric Evaluation for Assessing the Severity of Exercise-Induced Pulmonary Hemorrhage in Horses in Field Conditions.

Diagnosis and assessment of severity of exercise-induced pulmonary hemorrhage (EIPH) relies on postexercise visualization of fresh blood in the airways via tracheobronchoscopic examination (TBE) and/or counting erythrocytes in bronchoalveolar lavage fluid (BALFRBC). Determining the BALFRBC is more sensitive than TBE but its usefulness is hampered by the need to have BALFRBC counted at a laboratory. We explored the feasibility of evaluating the severity of EIPH by using a color chart comprised of five shades of red and matching those colors with the color of BALF immediately following collection. To validate the technique, sets of ten BALF samples with known BALFRBC numbers were created and randomly shown to two groups of 18 observers who independently matched the color of the BALF with one of the shades of red displayed on the screen of a smartphone. Interobserver and intra-observer agreements regarding colors were > 0.9. The utility of the color chart was further validated under field conditions at two barrel racing events where 63 BALF samples were collected from 21 horses and BALF color was graded independently by three observers. The number of BALFRBC in the 63 samples ranged from 25-1,100,000/µL. EIPH was diagnosed in 39 samples based on the detection of color, and all 5 colors were matched multiple times with BALF samples. Overall, the color of the BALF was related to the number of BALFRBC. Colorimetric evaluation of BALF represents a practical and reliable option for rapid postexercise assessment of the presence and severity of EIPH.

Effects of exercise, furosemide, blood depletion, and reinfusion on body fluid compartment volumes in horses.

High pulmonary blood pressure contributes to exercise-induced pulmonary hemorrhage. The objective of this study was to use bioimpedance spectroscopy to assess body fluid compartment volumes under 3 conditions in 6 racehorses: i) Pre- and post-supramaximal treadmill exercise (control); ii) Exercise 4 hours after furosemide (0.5 mg/kg body weight, IV); iii) Exercise, removal of ~14 L of blood and subsequent reinfusion of the blood. Statistical analysis used linear mixed effects models. Body compartment volumes did not change during the control runs. Total body water (TBW) (P = 0.007, P = 0.007), extracellular fluid (ECF) (P = 0.003, P = 0.003), and intracellular fluid (ICF) volumes (P = 0.04, P = 0.04) decreased pre- and post-exercise following furosemide administration. The ICF trended to decrease (P = 0.07) after slow removal of blood. Blood reinfusion increased TBW (P = 0.02, P = 0.02) and ICF (P = 0.005, P = 0.005) pre- and post-exercise.

Effets de l'exercice, du furosémide, de la diminution sanguine et de la ré-infusion sur les volumes des liquides corporels compartimentés chez les chevaux. Une pression sanguine pulmonaire élevée contribue à des hémorragies pulmonaires induites par l'exercice. L'objectif de la présente étude était d'utiliser la spectroscopie à bio-impédance pour évaluer les volumes des liquides corporels compartimentés sous trois conditions chez six chevaux de course : i) Pré- et post-supramaximal exercice au tapis roulant (témoin); ii) Exercice 4 h après administration de furosémide (0,5 mg/kg de poids corporel, IV); iii) Exercice, retrait d'environ 14 L de sang et ré-infusion subséquente du sang. Les analyses statistiques utilisaient des modèles linéaires à effets mixtes. Les volumes des compartiments corporels n'ont pas changé durant les essais témoins. Les volumes de la quantité totale d'eau corporelle (TBW) (P = 0,007, P = 0,007), de liquide extracellulaire (ECF) (P = 0,003, P = 0,003) et liquide intracellulaire (ICF) (P = 0,04, P = 0,04) ont diminué pré- et post-exercice à la suite de l'administration de furosémide. L'ICF avait tendance à diminuer (P = 0,07) à la suite du lent retrait de sang. La ré-infusion de sang augmenta la TBW (P = 0,02, P = 0,02) et l'ICF (P = 0,005, P = 0,005) pré- et post-exercice.(Traduit par Dr Serge Messier).

Equine Asthma: Current Understanding and Future Directions.

The 2019 Havemeyer Workshop brought together researchers and clinicians to discuss the latest information on Equine Asthma and provide future research directions. Current clinical and molecular asthma phenotypes and endotypes in humans were discussed and compared to asthma phenotypes in horses. The role of infectious and non-infectious causes of equine asthma, genetic factors and proposed disease pathophysiology were reviewed. Diagnostic limitations were evident by the limited number of tests and biomarkers available to field practitioners. The participants emphasized the need for more accessible, standardized diagnostics that would help identify specific phenotypes and endotypes in order to create more targeted treatments or management strategies. One important outcome of the workshop was the creation of the Equine Asthma Group that will facilitate communication between veterinary practice and research communities through published and easily accessible guidelines and foster research collaboration.

A wireless endoscopy capsule suitable for imaging of the equine stomach and small intestine.

BACKGROUND: Capsule endoscopy offers a new method for visualization of the gastrointestinal mucosa in horses where other imaging technologies have diagnostic limitations. OBJECTIVES: To (1) test the feasibility of using this novel endoscopy capsule to visualize intestinal mucosa in horses, including an objective assessment of image quality, (2) assess how changes in preadministration preparation affect the transit time and the amount of gastrointestinal mucosa visualized, and (3) describe intestinal mucosa lesions in healthy horses. ANIMALS: Five healthy adult horses. METHODS: Three protocols were used in a crossover study design. Protocols varied in time fasted, amount of oral fluid administered, and exercise. Manure was radiographically inspected for capsule recovery. Percentage of visible gastrointestinal mucosa was objectively assessed. RESULTS: Detailed images of the gastrointestinal mucosa were recorded with all 3 protocols, including images of the pylorus, major duodenal papilla, individual villi, and ileocecal junction. Visualization of large intestinal mucosa was poor. Interobserver agreement on image quality was excellent. Capsule administration after feed withholding for 24 hours provided the greatest percentage of visible mucosa in the stomach and small intestine. Total transit time to capsule excretion was 6.5 (3-8.75) days. Of 15 capsules administered, 3 were not recovered. Lesions visualized included mucosal erosion, ulceration and hemorrhage, areas of thickened mucosa, and evidence of parasitism. CONCLUSIONS: This novel endoscopic capsule appears safe, practical, and noninvasive in horses; however, variability in capsule excretion time must be taken into account for clinical application.

Comparison of physiological demands in Warmblood show jumping horses over a standardized 1.10 m jumping course versus a standardized exercise test on a track.

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.

Topography of the respiratory tract bacterial microbiota in cattle.

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.

Efficacy of dexamethasone, salbutamol, and reduced respirable particulate concentration on aerobic capacity in horses with smoke-induced mild asthma.

BACKGROUND: Mild asthma in horses decreases racing performance and impairs gas exchange. The efficacy of treatment on performance is unknown. HYPOTHESIS: Treatment targeting lung inflammation improves V ˙ O2 peak in horses with mild asthma. ANIMALS: Thoroughbred polo horses (n = 12) with smoke-induced mild asthma. Horses were exposed to increased ambient particulate matter (35.51 µg/m3 [PM2.5 ]; day mean, centrally measured) from day -33 to 0, from bushfire smoke (natural model). METHODS: Prospective, randomized, placebo-controlled, double-blinded clinical trial. All horses completed 3 V ˙ O2 peak tests, measuring aerobic and anaerobic variables: day 0 -baseline; day 16 -after dexamethasone (20 mg IM q24h; DEX, n = 6) or saline treatment (SALINE, n = 6), under improved ambient PM2.5 concentrations (7.04 µg/m3 ); day 17-15-30mins after inhaled salbutamol (1500 µg). Bronchoalveolar lavage and mucus scoring were performed on day -8 and day 20. Linear mixed effects models were used to examine the effects of timepoint and treatment group on BAL differential cell counts, mucus scores, aerobic and anaerobic variables. RESULTS: Horses' mucus scores improved significantly from day -8 to 20 by 1.27 ± .38 (P = .01). There was a significant increase in V ˙ O2 peak of 15.5 ± 4.0 mL(min.kg)-1 from day 0 to 17 (P = .002), representing an average (mean) increase in V ˙ O2 peak of 13.2%. There was no difference in V˙O2 peak between treatment groups (SALINE versus DEX) at any timepoint. CONCLUSIONS AND CLINICAL IMPORTANCE: This study highlighted the key role of improved air quality on functionally important airway inflammation. Evidence provided is central to increasing owner compliance regarding improved air quality for the treatment and prevention of mild asthma.

Conditioning equine athletes on water treadmills significantly improves peak oxygen consumption.

Equine water treadmills (WT) were initially designed for rehabilitation of musculoskeletal injuries, but are also commonly used for conditioning sport horses, however the effects are not well documented. The purpose of this study was to test the effect of an 18-day WT conditioning programme on peak oxygen consumption (V̇O2peak). Nine unfit Thoroughbreds were used in a randomised controlled trial. Six horses worked daily for 18 days in stifle-height water (WT group), while 3 control horses worked without water (dry treadmill group (DT)). Preconditioning and postconditioning maximal exercise racetrack tests (800 m) were performed using a portable ergospirometry system. Measured outcomes were V̇O2, tidal volume, minute ventilation, breathing frequency, heart rate, blood lactate and instantaneous and average speed. The workload as assessed by V̇O2 was 21.7 per cent of preconditioning V̇O2peak values for WT horses. V̇O2peak on the racetrack increased by 16.1 per cent from preconditioning to postconditioning in the WT horses (P=0.03), but did not change in the DT horses. Therefore, exercising horses in high water heights may improve conditioning.

Effects of nebulized dexamethasone on the respiratory microbiota and mycobiota and relative equine herpesvirus-1, 2, 4, 5 in an equine model of asthma.

BACKGROUND: Prolonged exposure to environmental antigens or allergens elicits an immune response in both healthy horses and those with mild asthma. Corticosteroids often are used to treat lower airway inflammation. OBJECTIVE: To investigate the changes in equine herpesvirus (EHV)-1,2,4,5 glycoprotein B gene expression and changes in respiratory bacterial and fungal communities after nebulized dexamethasone treatment of horses with asthma. ANIMALS: Horses with naturally occurring mild asthma (n = 16) and healthy control horses (n = 4). METHODS: Prospective, randomized, controlled, blinded clinical trial. Polymerase chain reaction amplification of EHV-1,2,4,5 in bronchoalveolar lavage fluid, and 16S (microbiome) and ITS2 (mycobiome) genes with subsequent sequencing was performed on DNA extracted from nasal swabs and transendoscopic tracheal aspirates before and after 13 days treatment with nebulized dexamethasone (15 mg q24h) and saline (control). RESULTS: Nebulized dexamethasone treatment decreased microbial diversity; relative abundance of 8 genera in the upper respiratory tract were altered. For both the microbiota and the mycobiota, environment had a dominant effect over treatment. Alternaria, an opportunistic pathogen and allergen in humans recognized as a risk factor for asthma, asthma severity, and exacerbations, was increased with treatment. Treatment affected relative quantification of the equine gamma herpesviruses (EHV-2 and -5); EHV-2 DNA levels increased and those of EHV-5 decreased. CONCLUSIONS: Nebulized dexamethasone treatment affected the upper respiratory tract microbiota, but not the mycobiota, which was overwhelmed by the effect of a sustained dusty environment.

Effect of injected dexamethasone on relative cytokine mRNA expression in bronchoalveolar lavage fluid in horses with mild asthma.

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-1ß, 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.