Signs of Heat Stress in Horses

Aug 1, 2019

With summer here and the warm weather calling, it´s easy to get carried away with long summer trail rides and fun-filled days competing, but it´s important to remember that our horses can suffer the adverse effects of the heat and sun, just as readily as we can. This is commonly referred to as heat stress in horses, or called heatstroke as for humans. It´s important to be aware of the signs of heatstroke and the measures that should be taken to prevent it in the first place.

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What actually is heat stress or heatstroke?

Heatstroke is the name given to the adverse effects of excessive heat that occur because the difference in temperature between the inside of the body and the ambient temperature is reduced. In some circumstances, the difference is actually reversed, so the outside temperature is hotter than body temperature. The bottom line is that the cooling mechanisms used by the body to regulate its temperature within normal range are no longer efficient and the body starts to overheat causing damage at many levels.

The horse is actually a vat of heat. All the digestion and fermentation processes that take place within its extensive gastrointestinal tract generate a huge amount of heat without the horse even doing anything. When the horse exercises it will rapidly generate heat through musculoskeletal activity. Even in cooler climates it´s easy for horses to overheat and cooling is still important after strenuous exercise, however in warmer and particularly more humid climates, this combination can be life-threatening if the horse isn´t cared for appropriately.

What are the signs of heat stress in the horse?

When the horse starts to overheat there is a steady deterioration in his physiological state, this can be so severe as to lead to coma or death so rapid identification of early signs is essential.

Excessive sweating is often seen first. Initially the horse will sweat more in an attempt to evaporate more water from the surface of the skin, sweating is a normal cooling mechanism for horses and generally, it´s very efficient. However, when the ambient temperature rises it becomes less and less effective.

In heat stress the horse will breathe faster in an attempt to reduce its body temperature through heat evaporation from the air it expels, monitoring horses for increased respiratory rates is important but remember that after exercise the respiratory rate will normally be elevated. For this reason, it´s a good idea to have an idea of how long it normally takes your horse´s breathing rate to return to normal after exercise at home.

Increased temperature is a key sign of heat stress, so even when traveling it´s important to keep a thermometer to hand. If the horse´s temperature starts to increase above normal range 99.6-101.5 F, then be aware that he might be suffering from heat stress.

Thermometer

As heat stress progresses not only are individual cells damaged from the rise in temperature but blood supply to internal organs alters and can lead to damage to the gastrointestinal tract and in more severe cases, to the brain. Signs of listlessness and progressive dullness in the early-mid stages of heat stress can progress to depression, recumbency, coma, and even seizures.

Treating heat stress

If your horse is suffering from heat stress, you need to work quickly to cool him down before further damage takes place. Call a veterinarian if he doesn´t seem to improve quickly

  • Bathing – one of the most effective forms of cooling is applying cool water, quickly scraping it off using a sweat scraper, and then reapplying in a rapid cycle to get the most from the cool water. Water that sits on the skin will rapidly heat up, so scraping off is important to maintain the difference in temperature that encourages evaporation and cooling

Sweat Scraper

  • Icing – careful application of ice packs, cold compresses or handy cool packs to the great vessels in the neck can help to cool the blood quickly. It´s important not to put ice directly to the skin if you have any doubt wrap the ice pack in a tea towel to protect the skin and tissues from cold damage

Cold Compress

  • Fanning – if a fan or cooled stabling area is available the horse should be moved there
  • Medication – anti-inflammatory medication may be prescribed in certain cases to help reduce temperature and alleviate secondary effects of heatstroke.

Cool pack

How to prevent heat stress

Heat stress can be prevented using a few careful steps. Providing shade in warm weather is very important so the horse can get out of the heat. Equally a source of cool water should always be available. Competing horses should be monitored for their thirst and be encouraged to drink regularly to help prevent dehydration and aid cooling. Some horses are very particular and get very used to their own buckets, so it´s often a good idea to invest in one or two sturdy ones and take one with you to competitions in case they refuse to drink from sources available onsite. Properly cooling the horse after exercise is very important, the most efficient method is using cool water to wash the horse down and scrape off as described above.

Bucket

It´s important especially in hot weather to maintain horses in ideal body condition, the presence of excess fat beneath the skin impairs the horses cooling mechanisms and basically acts to insulate him. It´s also important to take note of the stress of transport for competitions and the like. All the while being transported the horse is working and expending energy to counteract the movement of the truck, this is a workout for him and can lead to a rise in body temperature. Breaks for a short walk, cool off and water is even more important in warm weather.

When trail riding in summer, plan your rides for early mornings or late afternoons when the sun is not as hot and allow your horse frequent breaks.

Being aware of heat stress is important to help prevent it, horses are much more susceptible to overheating than under heating and having a few practices in place both at home and at the competition can go a long way to keeping your horse comfortable and healthy.

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