Characterization of exercise-induced hemolysis in endurance horses.

Exercise-induced hemolysis occurs as the result of intense physical exercise and is caused by metabolic and mechanical factors including repeated muscle contractions leading to capillary vessels compression, vasoconstriction of internal organs and foot strike among others. We hypothesized that exercise-induced hemolysis occurred in endurance racehorses and its severity was associated with the intensity of exercise. To provide further insight into the hemolysis of endurance horses, the aim of the study was to deployed a strategy for small molecules (metabolites) profiling, beyond standard molecular methods. The study included 47 Arabian endurance horses competing for either 80, 100, or 120 km distances. Blood plasma was collected before and after the competition and analyzed macroscopically, by ELISA and non-targeted metabolomics with liquid chromatography-mass spectrometry. A significant increase in all hemolysis parameters was observed after the race, and an association was found between the measured parameters, average speed, and distance completed. Levels of hemolysis markers were highest in horses eliminated for metabolic reasons in comparison to finishers and horses eliminated for lameness (gait abnormality), which may suggest a connection between the intensity of exercise, metabolic challenges, and hemolysis. Utilization of omics methods alongside conventional methods revealed a broader insight into the exercise-induced hemolysis process by displaying, apart from commonly measured hemoglobin and haptoglobin, levels of hemoglobin degradation metabolites. Obtained results emphasized the importance of respecting horse limitations in regard to speed and distance which, if underestimated, may lead to severe damages.

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.

Metabolic Predictors of Equine Performance in Endurance Racing.

Equine performance in endurance racing depends on the interplay between physiological and metabolic processes. However, there is currently no parameter for estimating the readiness of animals for competition. Our objectives were to provide an in-depth characterization of metabolic consequences of endurance racing and to establish a metabolic performance profile for those animals. We monitored metabolite composition, using a broad non-targeted metabolomics approach, in blood plasma samples from 47 Arabian horses participating in endurance races. The samples were collected before and after the competition and a total of 792 metabolites were measured. We found significant alterations between before and after the race in 417 molecules involved in lipids and amino acid metabolism. Further, even before the race starts, we found metabolic differences between animals who completed the race and those who did not. We identified a set of six metabolite predictors (imidazole propionate, pipecolate, ethylmalonate, 2R-3R-dihydroxybutyrate, ß-hydroxy-isovalerate and X-25455) of animal performance in endurance competition; the resulting model had an area under a receiver operating characteristic (AUC) of 0.92 (95% CI: 0.85-0.98). This study provides an in-depth characterization of metabolic alterations driven by endurance races in equines. Furthermore, we showed the feasibility of identifying potential metabolic signatures as predictors of animal performance in endurance competition.