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Australian veterinary journal2021; 99(11); 473-481; doi: 10.1111/avj.13108

An investigation into environmental variables influencing post-race exertional heat illness in thoroughbred racehorses in temperate eastern Australia.

Abstract: Exertional heat illness (EHI) is a syndrome that occurs when metabolic heat production from muscular contraction exceeds the rate at which it can be dissipated. Core body temperature rises to critical levels, causing hyperthermia and central nervous system dysfunction. Best practice for the prevention of EHI centres around early detection, rapid response and aggressive cooling. Advance planning enables risk mitigation measures. The more that is known about EHI in horses, the better prepared those in the positions of responsibility can be to anticipate events in which the risk of EHI may be elevated. This prospective, observational study investigated environmental risk factors associated with the occurrence of EHI. From 2014 to 2018, the number of horses exhibiting the symptoms of post-race EHI was recorded at 73 convenience sampled race meetings. Of the 4809 starters, the signs of EHI were recorded for 457. Thermal environmental data were measured and included ambient temperature, radiant heat, vapor pressure (humidity) and wind speed (WS). Mixed linear regression models were computed to assess the associations between the occurrence and incidence of post-race EHI and the four thermal environmental variables. The analysis showed that vapor pressure and WS had the largest effects on the occurrence of post-race EHI. The major limitations were that the race meetings selected were convenience sampled according to attendance by the first author and individual horse data were not available. EHI is influenced by a complex interaction of independently acting environmental variables, but warm, windless, humid days are most likely to result in the cases of EHI.
© 2021 Australian Veterinary Association.
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Publication Date: 2021-08-05 PubMed ID: 34355381DOI: 10.1111/avj.13108Google Scholar: Lookup
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  • Journal Article
  • Observational Study
  • Veterinary

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article studied the environmental variables that affect the occurrence of exertional heat illness (EHI) in thoroughbred racehorses in eastern Australia. It found that humidity and wind speed had the most significant effect on the incidence of EHI.

Research Objectives

  • The article aimed to examine the environmental risk factors associated with exertional heat illness (EHI) in thoroughbred racehorses.
  • The researchers intended to identify patterns and understand more about the circumstances under which EHI may be more likely to occur to aid in early detection and prevention of EHI.

Methodology

  • The study was carried out from 2014 to 2018 with data collected at 73 convenience sampled race meetings.
  • The team recorded the number of horses exhibiting symptoms of EHI post-race. In total, out of 4809 starters, 457 showed signs of EHI.
  • The thermal environmental data were measured, which included ambient temperature, radiant heat, vapor pressure (humidity), and wind speed.
  • A mixed linear regression model was used to analyze the associations between the occurrence of post-race EHI and the different thermal environmental components.

Results

  • The research determined that the two most significant factors affecting the occurrence of post-race EHI were vapor pressure (humidity) and wind speed.
  • According to the findings, it indicates that on warm, windless, and humid days, cases of EHI are more likely to occur.

Limitations

  • The primary constraint of this study was that the race meetings were chosen according to the availability of the first author, rather than being randomly sampled.
  • Another significant limitation was the lack of data on individual horse factors, which may also play a significant role in EHI occurrence. These may include factors such as the horse’s age, weight, or race history.

Implications

  • Understanding the environmental factors that could increase the risk of EHI can help horse handlers, jockeys, and stakeholders to better plan for and manage the horses’ health and safety during race events.
  • However, future research should include individual horse-related data to provide a more comprehensive understanding of the risks associated with EHI.

Cite This Article

APA
Brownlow MA, Brotherhood JR. (2021). An investigation into environmental variables influencing post-race exertional heat illness in thoroughbred racehorses in temperate eastern Australia. Aust Vet J, 99(11), 473-481. https://doi.org/10.1111/avj.13108

Publication

Australian veterinary journal
ISSN: 1751-0813
NlmUniqueID: 0370616
Country: England
Language: English
Volume: 99
Issue: 11
Pages: 473-481

Researcher Affiliations

Brownlow, M A
  • Racing Australia, Druitt Street, Sydney, New South Wales, 2000, Australia.
Brotherhood, J R
  • Discipline of Exercise and Sports Science, School of Health Sciences, Faculty of Medicine and Health, University of Sydney, Australia.

MeSH Terms

  • Animals
  • Heat Stress Disorders / epidemiology
  • Heat Stress Disorders / veterinary
  • Horse Diseases / epidemiology
  • Horse Diseases / etiology
  • Horses
  • Hot Temperature
  • Incidence
  • Prospective Studies
  • Risk Factors

Grant Funding

  • University of Sydney

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Citations

This article has been cited 4 times.
  1. Trigg LE, Lyons S, Mullan S. Risk factors for, and prediction of, exertional heat illness in Thoroughbred racehorses at British racecourses.. Sci Rep 2023 Mar 14;13(1):3063.
    doi: 10.1038/s41598-023-27892-xpubmed: 36918525google scholar: lookup
  2. Brownlow M, Mizzi JX. An Overview of Exertional Heat Illness in Thoroughbred Racehorses: Pathophysiology, Diagnosis, and Treatment Rationale.. Animals (Basel) 2023 Feb 9;13(4).
    doi: 10.3390/ani13040610pubmed: 36830397google scholar: lookup
  3. Verdegaal EJMM, Howarth GS, McWhorter TJ, Delesalle CJG. Is Continuous Monitoring of Skin Surface Temperature a Reliable Proxy to Assess the Thermoregulatory Response in Endurance Horses During Field Exercise?. Front Vet Sci 2022;9:894146.
    doi: 10.3389/fvets.2022.894146pubmed: 35711810google scholar: lookup
  4. Kang H, Zsoldos RR, Skinner JE, Gaughan JB, Mellor VA, Sole-Guitart A. The Use of Percutaneous Thermal Sensing Microchips to Measure Body Temperature in Horses during and after Exercise Using Three Different Cool-Down Methods.. Animals (Basel) 2022 May 14;12(10).
    doi: 10.3390/ani12101267pubmed: 35625113google scholar: lookup
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