As the thermometer rises, keeping your horse cool becomes more than a matter of comfort - it’s vital for their wellbeing.
This means both we and our horses are unlikely to be acclimatised to the temperatures this brings. Given time, horses can become accustomed to extremes of temperature and some breeds have evolved to be particularly efficient at this, a prime example being the Arab horse in the desert, where a 30-degree shift in day-night temperature is not unusual.
Particular problems arise when the horse has to work in extreme heat. Horses have a relatively large muscle mass and low surface area to mass ratio. Heat is lost by radiation and evaporation of sweat, so it is a disadvantage to be large and muscular if you need to lose heat quickly. To enhance heat exchange, blood vessels in the skin dilate, bringing warm blood closer to the surface where heat can be dissipated. This response is especially noticeable in racehorses after intense exercise, but the same physiological mechanisms are present even in small, hairy ponies. Cooling will only occur when there is a heat “gradient” or difference between the horse and its surroundings, with cooling occurring dramatically when the air temperature is around 30 degrees. Heat is also lost through respiration; the respiratory rate may rise a little, especially if the lungs are compromised in some way, such as horses who may have inflammatory airway disease or asthma.
Most people will be doing the sensible thing of avoiding exercise on the hottest part of the day, by providing ad lib water for their horses and some degree of shade, or bringing them in during the day. Water consumption increases in hot weather to compensate for the fluid lost through sweating and evaporation from the respiratory system. It is obviously cooler in the shade but if stabled, it is absolutely essential to have adequate ventilation. Traditional stables, especially of wooden construction, can easily heat up and become saunas. The use of electric fans can provide a welcome breeze. In hot weather, it can be advantageous to add water to the feed and provide wet hay as this can increase water intake. Forage holds fluid and provides a reservoir in the hindgut. In cases where there is insufficient water intake or the horse is particularly hot, the fluid absorbed from the gut can be excessive and impaction colic can result. If the horses are out in the field with self-filling troughs, these should be checked regularly as they often go green with algae in hot weather and the water becomes unappetizing to some.
Electrolytes, which are essential for muscle function, are lost in sweat. In hot weather, a tablespoon of kitchen salt in feed will help to replenish this or you may choose to use commercially available electrolyte preparations. These can be given in water, but additional fresh water should also always be available as some horses do not like the taste of electrolytes.
There are occasions when riding in the heat of the day is unavoidable, especially if you are competing. It is important to be adequately prepared - take plenty of water from home even if there is some available at the venue. Some horses will not drink strange water! Another tip is to take the horse’s own water bucket from the stable. We’ve all heard of horses who will not drink “home” water in a “strange” bucket! If you have the option, park your vehicle where there is shade. Ensure all the windows are open and put the ramp down. Should you be fortunate enough to have electric fans in your lorry, run them every so often. If attending to the horse outside of the horsebox, do so in the shade. Have drinking water available at all times that you are not riding. Allow the horse access to forage as this will help hold water which will be absorbed from the gut when required.
Much research was carried out before the Olympics on cooling horses after exercise. In the larger events, we now see tents with fans emitting cooling mists but your yard or local show centre is highly unlikely to have such luxury! The best method in this situation is to apply copious amounts of water over the neck and body. More recently, there has been debate surrounding whether it is necessary to scrape off excess water afterwards, over concerns water magnifies in the sun or heats up as it evaporates. There is no truth to this and whilst scraping off excess water is not likely to be detrimental to the cooling process, to cool your horse most effectively, this time is better spent applying additional water to them.
Under no circumstances should cold towels be placed over the neck, as these rapidly become hot towels and there is no facility for evaporation. Offer water as soon as you have finished your round or ride and encourage him to drink. If your horse is a particularly sweaty type and you are competing regularly it is probably better to clip him out as it will be easier to keep him cool. This is probably not an option for show horses but showjumpers can be regularly clipped all year round.
By far the most important thing in this weather is keeping your horse cool but other problems can arise, particularly in bright sunlight. Horses are just as susceptible as humans to sunburn and pink noses should always be protected. A full-face mask which reaches over the nose is useful if the horse is out at grass, while also keeping flies away from the eyes. However, it is advisable to also apply sunblock. Factor 50 (designed for children) is the best and should be applied regularly.
Flies, both biting flies such as horseflies and nuisance ones around the eyes are always worse during the summer and a good fly repellent is essential. A pyrethrin-based fly repellent applied over the entire horse is the most effective option, as it offers longer-lasting protection and can also help guard against midges - particularly important for horses suffering from sweat itch. Fly repellent is essential if your horse has sarcoids or shares premises with one that does, since flies play a major role in spreading these unpleasant tumours by carrying the virus from one site to another, either on the same horse or to a different, susceptible individual. Many people find fly rugs useful, some of which come impregnated with pymerthrin to repel flies and being white or light in colour they do help to reflect the sun’s rays and so may aid a little in cooling.
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