Continuous Monitoring of the Thermoregulatory Response in Endurance Horses and Trotter Horses During Field Exercise: Baselining for Future Hot Weather Studies.
Abstract: Establishing proper policies regarding the recognition and prevention of equine heat stress becomes increasingly important, especially in the face of global warming. To assist this, a detailed view of the variability of equine thermoregulation during field exercise and recovery is essential. 13 endurance horses and 12 trotter horses were equipped with continuous monitoring devices [gastrointestinal (GI) pill, heartrate (HR) monitor, and global positioning system] and monitored under cool weather conditions during four endurance rides over a total of 80 km (40 km loops) and intense trotter track-based exercise over 1,540 m. Recordings included GI temperature (T ), speed, HR and pre- and post-exercise blood values. A temperature time profile curve of T was constructed, and a net area under the curve was calculated using the trapezoidal method. Metabolic heat production and oxygen cost of transport were also calculated in endurance horses. Maximum T was compared using an independent samples -test. Endurance horses (mean speed 14.1 ± 1.7 km h) reached mean maximum T (39.0 ± 0.4°C; 2 × 40 km in 8 horses) during exercise at 75% of completion of T exercise and T returned to baseline within 60 min into recovery. However, the mean T was still 38.8 ± 0.4°C at a HR of 60 bpm which currently governs "fit to continue" competition decisions. Trotters (40.0 ± 2.9 km h) reached a comparable mean max T (38.8 ± 0.5°C; 12 horses) always during recovery. In 30% of trotters, T was still >39°C at the end of recovery (40 ± 32 min). The study shows that horses are individuals and thermoregulation monitoring should reflect this, no matter what type of exercise is performed. Caution is advised when using HR cut-off values to monitor thermal welfare in horses since we have demonstrated how T can peak quite some time after finishing exercise. These findings have implications for training and management of performance horses to safeguard equine welfare and to maximize performance.
Copyright © 2021 Verdegaal, Howarth, McWhorter, Boshuizen, Franklin, Vidal Moreno de Vega, Jonas, Folwell and Delesalle.
Publication Date: 2021-08-26 PubMed ID: 34512382PubMed Central: PMC8427666DOI: 10.3389/fphys.2021.708737Google Scholar: Lookup
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Summary
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The research investigates how endurance and trotter horses manage their body temperature during and after exercise under cool weather. It provides detailed information on how horse thermoregulation varies during field exercises and recovery, which has implications for properly recognizing and preventing equine heat stress in an increasingly warm environment.
Methodology
- The study involved 13 endurance horses and 12 trotter horses, which were equipped with continuous monitoring devices. These devices monitored gastrointestinal temperature, heart rate, and tracked the horse’s position via a global positioning system.
- The horses were subjected to field exercises under cool weather conditions. Endurance horses were made to go through four endurance rides, covering a total distance of 80 km, while the trotter horses underwent intense track-based exercises over 1,540 m.
- Throughout the exercises, several recordings were taken, including the gastrointestinal temperature, speed, heart rate, and blood values before and after exercise.
- To analyze the data, a temperature time profile curve was constructed and a net area under the curve was calculated using the trapezoidal method. For the endurance horses, metabolic heat and oxygen transport costs were also calculated.
- The maximum gastrointestinal temperatures of the two types of horses were compared using an independent samples T-test.
Findings
- Endurance horses reached their mean maximum gastrointestinal temperature during exercise at about 75% of completion, then returned to their baseline temperature within 60 minutes of recovery. However, their average temperature was approximately 38.8°C at a heart rate of 60 bpm, which is currently the threshold used to decide whether a horse is “fit to continue” competition.
- On the other hand, trotter horses reached a similar mean maximum gastrointestinal temperature, but this usually occurred during recovery rather than the exercise period. Even at the end of recovery, the gastrointestinal temperature of roughly 30% of the trotters was still above 39°C.
- Overall, the study’s authors cautioned against using heart rate cutoff values to monitor a horse’s thermal well-being, as they found that peak gastrointestinal temperature can occur some time after the end of an exercise session.
Implications
- The study’s findings underscore the importance of individualized monitoring of thermoregulation in horses, regardless of the type of exercise they perform.
- The delay in peak gastrointestinal temperature has implications for training and managing performance horses to protect their welfare and optimize performance.
- The research has also raised questions regarding the currently used “fit to continue” competition thresholds based on heart rate and highlights the need for more comprehensive health monitoring strategies.
Cite This Article
APA
Verdegaal EJMM, Howarth GS, McWhorter TJ, Boshuizen B, Franklin SH, Vidal Moreno de Vega C, Jonas SE, Folwell LE, Delesalle CJG.
(2021).
Continuous Monitoring of the Thermoregulatory Response in Endurance Horses and Trotter Horses During Field Exercise: Baselining for Future Hot Weather Studies.
Front Physiol, 12, 708737.
https://doi.org/10.3389/fphys.2021.708737 Publication
Researcher Affiliations
- Equine Health and Performance Centre, University of Adelaide, Adelaide, SA, Australia.
- School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Adelaide, SA, Australia.
- Research Group of Comparative Physiology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
- School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Adelaide, SA, Australia.
- School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Adelaide, SA, Australia.
- Research Group of Comparative Physiology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
- Equine Health and Performance Centre, University of Adelaide, Adelaide, SA, Australia.
- School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Adelaide, SA, Australia.
- Research Group of Comparative Physiology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
- School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Adelaide, SA, Australia.
- School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Adelaide, SA, Australia.
- Research Group of Comparative Physiology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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