The heat is on at Badminton – in more ways than one

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The higher the temperature or humidity the more effort the horse will have to put in to try to limit its body temperature from getting too high. This in turn means that the capacity to exercise may be reduced and horses may fatigue earlier.
The higher the temperature or humidity the more effort the horse will have to put in to try to limit its body temperature from getting too high. This in turn means that the capacity to exercise may be reduced and horses may fatigue earlier. © David Marlin

If you believe the weather forecasts (and we have good reason to have some doubt there!) we are in for a mini-heatwave this weekend to coincide with the 2016 Badminton Horse Trials.

In fact, the UK is predicted to be hotter than Ibiza with temperatures into the mid 20°Cs. Whilst this may be good for spectators, organisers and the shops at Badminton, what implication could it have for horses and riders?

Physiologically horses cope quite well with environmental temperatures from 5°C up to around 25°C, provided that as it gets warmer the humidity stays low. In the UK, temperatures above 20°C are rarely associated with high humidity as they are in places such as the southern US states or even Kentucky. However, the higher the temperature and/or humidity, the more effort the horse will have to put in to try to limit its body temperature from getting too high. This in turn means that the capacity to exercise may be reduced and horses may suffer from fatigue earlier. The impact of thermal environmental conditions is greater depending on the thermal load (high temperature or moderate temperature and moderate to high humidity) but is also dependent on how hard and for how long the horse exercises.

endurance-groom-water_2150If we take the three different phases, the weather on the day will not affect each one in the same way. For example, the showjumping phase is very short and it is unlikely that the temperature at the weekend,even if it gets to 25°C, will have any affect at all. In fact, muscles perform slightly better and take less time to warm-up so it could even be beneficial to have a warmer day.

For dressage, as most of the horses spend a fair amount of time being ridden in, they can get quite warm. This in turn can take the edge of some horses, which some riders may well appreciate!

However, it’s the cross-country where the biggest potential effect of a sudden jump in temperatures this weekend could have the biggest implication as not only are the horses warmed-up, they work hard and for longer than 10 minutes. Here, horses who are not acclimatised to warmer weather may well tire earlier and be more inclined to make mistakes.

Another important factor in determining how horses will cope with warmer weather is related to breed and size. For example, Thoroughbred or part-Thoroughbred or Arab or part-Arab horses cope better with heat than Warmbloods. Furthermore, size plays a role as well and in warmer weather smaller horses have an advantage over larger horses as they can get rid of heat easier and more quickly.

When most people think of acclimatisation of horses they will probably think of competing in Florida or Spain in the Summer, the Atlanta Olympics or even Rio 2016. However, each year as we go from Winter into Spring and into Summer horses have to “acclimatise” to the warmer conditions. This process takes around three weeks.

But whilst horses do acclimatise simply by living in warmer temperatures, the majority of the acclimatisation effect that will help them cope better with exercising in warm weather comes from … surprise, surprise, exercising in warm weather.

The risk is when we get a period of relatively cold weather and then a sudden jump as we may face this week going into Badminton. If we look at the average temperature for the past month for Badminton (based on the weather station at Sherston, just a few miles away) we can see that the average temperature has been 8.1°C! So it’s very unlikely that many horses based in the UK being prepared for Badminton will have been trained at anything approaching 25°C.

So what should riders do to help their horses in these circumstances? For Badminton this weekend, nothing.

If they started to try to acclimatise by working their horses in the warmer weather or galloping with rugs on (I developed this for British teams for the Atlanta Olympics and it’s still used by the British Team in preparation for travel to hot climates) then this would be detrimental for several reasons. Firstly, if anything they should be tapering (reducing workload). Secondly, horses tend to become worse before they become better as you start acclimatisation. Thirdly, there is not enough time for it to have any effect in any case; two weeks would be a minimum.

Misting systems have been used in hot and humid areas to help cool down sport horses during competitions.
Misting systems have been used in hot and humid areas to help cool down sport horses during competitions. © David Marlin

What riders can do is to change their management at the event. If the horse is becoming too hot during warming-up, then it may be prudent to stop and do some cooling with iced-water. Riders may also choose to slightly shorten their normal warm-up. On the cross-country if it is a warm day with temperatures hitting 25°C as predicted, the riders who can tell that their horse is starting to fatigue earlier than expected and take appropriate action are likely to have a better chance of a safe completion. The danger will be in the last third of the course.

With respect to welfare, cooling horses rapidly and immediately they finish the cross-country is vital to reduce the risk of horses collapsing. Horses can become very hot during the cross-country, especially in moderately warm weather and when not acclimatised. Whilst on the cross-country the majority of the blood is pumped to the muscles. However, as they pull up the blood is redirected from the muscles to the skin to try to get rid of heat. The effect of this is to cause a sudden drop in blood pressure and this can lead to a horse collapsing with the risk of injury.

The good news is that vets and organisers at high level three-day events are aware of the risks of thermal conditions and since the research in the lead-up to the Atlanta Olympic Games in 1996, heat related injury has become relatively rare.

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David Marlin

Dr Marlin has worked with the FEI (Fédération Equestre Internationale) and IOC (International Olympic Committee) and as a consultant to the British Equestrian Teams since 1994 and has been a member of the World Class Performance Scientific Advisory Group. » Read David’s profile

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