When is it too hot for horses?
What temperature is too hot for horses?
How hot can horses tolerate?
How to spot when a horse is too hot?
How to spot a hot horse?
These are some of the questions I get asked all the time and with lots of conflicting advice on the internet and social media it’s easy to understand why owners may be confused. Just in case you are not aware of my credentials to write advice on this topic, I worked for the FEI before the 1996 Atlanta Olympic Games on the management of horses in thermally challenging environments. I have also published a larger number of research papers on this topic and have been involved as an advisor to the FEI at the Athens, Beijing and Tokyo Olympic Games as well as a number of World Equestrian Games.
Horses do exist in some of the coldest and hottest places on earth. But breeds in the hottest climates tend to be thinner and more angular, for example, Arabians, as opposed to the heavier draught or Warmblood types. So the Arabian and Thoroughbred type horses are naturally more suited to hot climates. If you live in a temperate climate, such as the UK, then summer temperatures of 20-25°C pose little problem to most horses. However, sudden heatwaves are a risk, particularly for older horses, young horses, overweight horses and horses with long-term health issues such as heart disease or equine asthma or Cushings. Sudden heatwaves are also a problem as horses and ponies will not be adapted or acclimatised to the higher heat. This takes several months of living at higher temperatures or several weeks of training. So for example, a fit event horse that is coping fine in normal summer weather may really struggle if asked to do the same work when it’s 10-15°C warmer. Acclimatisation will help to some degree, but a reduction in exercise capacity will be inevitable. If in any doubt, the safest approach is to clearly avoid exercising in the hotter part of the day unless you are aiming to acclimatise.
Even at rest, some horses and ponies may be uncomfortable in the heat. Some horses and ponies may be better off outside compared with inside depending on the stable construction and materials. For example, wooden stables with black felt roofs can be very hot in the day in summer whereas old brick stables with high ceilings may be much cooler than outside. To make horses and ponies more comfortable spraying them all over with water and allowing them to dry naturally can make a big difference. If they have to wear fly rugs then these can also be wetted down to increase comfort.
How much heat an animal produces during exercise is related to its oxygen consumption. Horses are able to use oxygen 2-3 times faster than we can, even allowing for differences in size. They, therefore, produce heat 2-3 times faster than we do. Horses are large animals and as such find it more difficult to get rid of heat than people for example. The majority of heat loss in people and horses occurs at the body surface. So whilst a horse is 6-7 times larger than a person it only has 2.5 times more skin surface – this is great for keeping warm in cold weather but not optimal for getting rid of body heat in hot weather. The horse has evolved however to sweat more than any other animal. Horses are also able to tolerate much higher body temperatures than we can. So whilst a person would be seriously ill with a body temperature of 40°C a horse can tolerate 42.5°C for short periods of time.
Horses that have become too hot can easily be spotted. Firstly, they will be covered all over in sweat and the blood vessels in the skin will be raised. They will be “blowing” hard – very deep and noisy breathing with flared nostrils. They will feel hot to touch and may also be excited or alternatively appear unaware of or unreactive to their surroundings. They are also often unsteady on their feet (ataxic). Keeping them slowly walking with gentle turns can help reduce the risk of horses going down. Finally, if a rectal temperature is taken it is likely that this will show above 40°C. When horses finish exercising the rectal temperature lags behind that of the muscles as heat is “moved” around the body. So a horse that finishes a race or competition at 40°C may easily increase to 41°C or more over the next 5-10 min as the rectal temperature “catches up” with the rest of the body.
The higher the temperature the more urgent the need to cool the horse down. Cooling should start without delay and even before a rectal temperature is taken. The most effective way is to continually cover as much of the horse with water for 5-10 min before stopping to review how the horse is doing. It is a waste of time trying to cool specific areas such as large veins. If you have access to cold water that will cool the horse quicker with no risk. But even cool water at say 30°C will bring a horse’s temperature down; it will just take more water and longer. If you are using a hose then don’t forget to run it in case the water inside has been heated up in the sun. If in doubt seek veterinary advice.
More Information:
- Article – Best Practice for horses in a Heatwave
- Video – Why you should NOT scrape water off when cooling a hot horse explained in 30s
- Article – Hot weather advice – Keep your horse safe in hot weather
- Video – Surviving the heat!
- Article – Health Warning! Advice to keep you and your horse safe in warm or hot weather
- Article – What’s the Best Method to Cool a Hot Horse?
- Video – Cooling and scraping and its effect on a horse’s surface temperature
- News Video – Training For Tokyo – Cooling by Dr David Marlin
- Article – Managing and Feeding Horses to Maintain Health in Hot & Humid Weather
- Research Paper PrePrint – Evaluation of the Cooling Efficacy of Different Equine Leg Cooling Methods
