Can racehorses overheat?

The short answer is yes, they certainly can. When performing strenuous exercise, especially on hot, humid days, racehorses may be pushed beyond the limits of their recovery mechanisms and suffer incidents of overheating. Otherwise known as extertional heat illness, heat stress or hyperthermia, overheating typically occurs immediately post-race and is characterised by obvious signs of distress, elevated heart and respiration rates and profuse sweating.

In extreme cases, overheating can put horses into a state of medical shock, such that their organs and cells, including muscle cells, stop functioning properly. Symptoms may include unpredictable behaviour and gait, stumbling, collapse and convulsion, but medical shock is a life-threatening condition, so racehorses with serious overheating should always be considered a veterinary emergency.

Sweating is a much less effective cooling mechanism in horses than in human beings, such that during the Summer – or, indeed, during unseasonably warm weather at other times of year – racecourses take precautions to prevent heat-related problems in horses. Such precautions include the provision of plentiful, easily accessible water supplies, for washing down and drinking, in all horse areas and, if possible, additional shaded cooling areas, available pre- and post-race. Indeed, many British racecourses have also installed high-pressure misting fans, which draw heat from the surrounding air and allow horses to cool more quickly during washing down.

The British Horseracing Authority (BHA) is unfraid to abandon racing altogether, on welfare grounds, if temperatures are deemed unsafe. In July 2022, for example, the BHA abandoned five fixtures, at Beverley, Windsor, Chelmsford, Southwell and Wolverhampton, after an extreme heat warning was issued by the Met Office.