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.

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.

Long-term follow-up of laryngeal Rhinosporidium seeberi diagnosed by PCR and treated with laser ablation and voriconazole nebulization in a retired thoroughbred polo horse.

A 21-year-old retired polo Argentinian thoroughbred horse from a teaching herd was presented for a routine bronchoalveolar lavage demonstration, during which an incidental finding of a granulomatous mass on the dorsal aspect of the epiglottis was made. Rhinosporidium seeberi was suspected from a histological section obtained from an initial biopsy, and the mass was removed via laser surgery for cytology and PCR. Sequencing of the PCR amplicons confirmed the diagnosis of R. seeberi. A treatment protocol of nebulized voriconazole for 10 d postoperatively was used. Long-term follow-up required 2 more laser surgeries plus oral fluconazole to resolve the remaining fungal spores. However, 2.5 y later, there was no evidence of remaining fungal spores. Key clinical message: Horses from endemic regions can potentially be exposed to R. seeberi. Based on its travel history, this horse may have contracted the infection in South America, California, or Alberta. Treatments administered, including diode laser resection, voriconazole antifungal nebulization, and oral fluconazole administration, were successful but required repeated interventions.

Suivi à long terme du Rhinosporidium seeberi laryngé diagnostiqué par PCR et traité par ablation au laser et nébulisation au voriconazole chez un cheval de polo thoroughbred pur-sang à la retraiteUn cheval thoroughbred argentin de polo retraité de 21 ans, issu d'un troupeau d'enseignement, a été présenté pour une démonstration de lavage broncho-alvéolaire de routine, au cours de laquelle une découverte fortuite d'une masse granulomateuse sur la face dorsale de l'épiglotte a été faite. Rhinosporidium seeberi a été suspecté à partir d'une coupe histologique obtenue à partir d'une biopsie initiale, et la masse a été retirée par chirurgie au laser pour cytologie et PCR. Le séquençage des amplicons PCR a confirmé le diagnostic de R. seeberi. Un protocole de traitement au voriconazole nébulisé pendant 10 jours après l'opération a été utilisé. Le suivi à long terme a nécessité 2 autres interventions chirurgicales au laser et du fluconazole oral pour éliminer les spores fongiques restantes. Cependant, 2,5 ans plus tard, il n'y avait aucune trace de spores fongiques restantes.Message clinique clé:Les chevaux des régions endémiques peuvent potentiellement être exposés à R. seeberi. D'après ses antécédents de voyage, ce cheval pourrait avoir contracté l'infection en Amérique du Sud, en Californie ou en Alberta. Les traitements administrés, notamment la résection au laser à diode, la nébulisation antifongique au voriconazole et l'administration orale de fluconazole, ont été efficaces mais ont nécessité des interventions répétées.(Traduit par Dr Serge Messier).

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.

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).

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.

Water treadmill exercise reduces equine limb segmental accelerations and increases shock attenuation.

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.

Assessment of body fluids and blood parameters associated with rapid weight change in heavy horses.

Horses competing in pulling competitions often undergo rapid weight change to enter lower weight categories. The aim of this study was to assess weight change and the associated changes of body water compartments in pulling horses. Weight change was attributed primarily to body water losses; however, losses from other sources were also indicated.

Évaluation des liquides organiques et des paramètres sanguins avec un changement rapide de poids chez les chevaux lourds. Les chevaux participant à des compétitions de trait subissent souvent des changements de poids rapides pour s'inscrire à des catégories de poids inférieurs. Le but de cette étude consistait à évaluer le changement de poids et les changements connexes de l'eau dans les compartiments du corps chez les chevaux de trait. Le changement de poids a été principalement attribué à la perte d'eau corporelle. Cependant, des pertes d'eau d'autres sources ont aussi été signalées.(Traduit par Isabelle Vallières).

Determination of body proportion factor in draft horses for the use of bioimpedance spectroscopy.

Bioelectrical impedance spectroscopy (BIS) instantly assesses body composition to monitor the effects of diet, competition, and illness, though it requires a body proportion factor (Kb). This study aimed to validate a draft horse-specific Kb. The calculated Kb was 1.42, resulting in significantly lower body composition values, with the exception of fat mass.

Détermination du facteur de proportion corporelle chez les chevaux de trait pour l'utilisation d'une spectroscopie de bio-impédance. Une spectroscopie de bio-impédance bioélectrique (SBB) évalue instantanément la composition corporelle pour surveiller les effets de la diète, de la compétition et de la maladie, même si elle exige un facteur de proportion corporelle (Kb). Cette étude visait à valider un Kb spécifique aux chevaux de trait. Le Kb calculé était de 1,42, ce qui a produit des valeurs de composition corporelle significativement inférieures, à l'exception de la masse de graisse.(Traduit par Isabelle Vallières).

Reversible dysphagia secondary to guttural pouch mycosis in a gelding treated medically with voriconazole and surgically with carotid occlusion and esophagostomy.

A gelding was diagnosed with dysphagia and left guttural pouch mycosis. Treatments included topical antifungal drugs, systemic voriconazole, and balloon occlusion of the internal carotid artery. Ongoing dysphagia of neurological origin necessitated extra-oral feeding through an esophagostomy tube. Complementary case management included acupuncture. Clinical remission occurred over 10 weeks.

Dysphagie réversible secondaire à une mycose de la poche gutturale chez un hongre traité médicalement avec du voriconazole et chirurgicalement par l'occlusion de la carotide et l'œsophagostomie. Un hongre a été diagnostiqué avec de la dysphagie et une mycose de la poche gutturale gauche. Les traitements ont inclus des médicaments antifongiques topiques, du voriconazole systémique et l'occlusion par ballon de l'artère carotide interne. Une dysphagie non résorbée d'origine neurologique a nécessité une alimentation extra-orale par un tube d'œsophagostomie. Une gestion du cas complémentaire a inclus l'acupuncture. Une rémission clinique s'est produite pendant 10 semaines.(Traduit par Isabelle Vallières).

Upper and lower respiratory tract microbiota in horses: bacterial communities associated with health and mild asthma (inflammatory airway disease) and effects of dexamethasone.

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.

High intensity, short duration pulling in heavy horses: physiological effects of competition and rapid weight change.

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.

Workload of horses on a water treadmill: effect of speed and water height on oxygen consumption and cardiorespiratory parameters.

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.

FEASIBILITY FOR ULTRASOUND-GUIDED INJECTION OF THE COLLATERAL LIGAMENTS OF THE DISTAL INTERPHALANGEAL JOINT IN HORSES.

Desmitis of the collateral ligament of the distal interphalangeal joint is a cause of lameness in performance horses. The objective of this prospective, experimental, ex vivo feasibility study was to evaluate the success of ultrasound-guided injection of the collateral ligaments of the distal interphalangeal joint in the equine forelimb. Seventy-six ultrasound-guided dye injections of the collateral ligament of the distal interphalangeal joint were performed on horses' cadaver limbs. The hooves were sectioned transversely to verify the location of the dye relative to the collateral ligaments and surrounding structures. Evaluations of transverse sections were performed independently by two experienced observers. A scoring system was used to assess injection of the collateral ligament of the distal interphalangeal joint at the proximal, middle, and distal aspect over the length of the ligament. The collateral ligament was injected at any point in 97.4% of cases. The ligament was injected over the entire scored length in 43.2% of cases (32/74), over two scored length areas in 45.9% of cases (34/74), and in one area in 10.8% of cases (8/74). The distal interphalangeal joint and the common digital extensor tendon were also injected in 81.6% (62/76) and 43.4% (33/76) of the cases, respectively. Use of the ultrasound had a positive and negative predictive value of 98% and 9%, respectively. In this study, ultrasound guidance was useful for confirming injection of the collateral ligament of the distal interphalangeal joint but did not prevent injecting the distal interphalangeal joint and the common digital extensor tendon.

Is Corynebacterium pseudotuberculosis infection (pigeon fever) in horses an emerging disease in western Canada?

This report describes 5 horses in the southern Alberta region with typical and atypical external abscessation due to Corynebacterium pseudotuberculosis (pigeon fever). "Pigeon fever" has recently been diagnosed in new geographic regions in North America and should be kept as a differential diagnosis by practitioners when an external or internal abscess is identified in a horse.

L'infection parCorynebacterium pseudotuberculosis(fièvre du pigeon) chez les chevaux est-elle une maladie émergente dans l'Ouest canadien? Ce rapport décrit cinq chevaux dans la région sud de l'Alberta atteints d'abcès externes typiques et atypiques causés par Corynebacterium pseudotuberculosis (fièvre du pigeon). La «fièvre du pigeon¼ a récemment été diagnostiquée dans de nouvelles régions géographiques de l'Amérique du Nord et devrait être conservée comme diagnostic différentiel par les praticiens lorsqu'un abcès externe ou interne est identifié.(Traduit par Isabelle Vallières).

Evaluation of coagulation via thromboelastography in healthy horses administered dexamethasone.

Dexamethasone was administered to healthy horses daily for 7 days. Blood samples were collected at 3 time points from both treatment and non-treatment groups, and analyzed via thromboelastography (TEG). There were no significant differences in TEG parameters between treated and untreated horses, or within treatment groups over time.

Évaluation de la coagulation par une thrombo-élastographie chez des chevaux en santé ayant reçu de de la dexaméthasone. La dexaméthasone a été administrée à des chevaux en santé pendant 7 jours. Des échantillons de sang ont été prélevés à trois moments auprès des groupes de traitement et des groupes sans traitement et ensuite analysés par thrombo-élastographie (TEG). Il n'y avait aucune différence significative dans le temps pour les paramètres TEG entre les chevaux traités et non traités ou à l'intérieur des groupes de traitement.(Traduit par Isabelle Vallières).

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.

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.

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.