Equine Heat Stress – How to avoid

During Summer with scorching temperatures it is important to avoid equine heat stress.

It is all about your horse being able to maintain his core body temperature close to 37.5C. This he can efficiently do on his own under most environmental conditions provided he has choices, for example access to shade and a clean trough that dispenses nice, cool water.

Heat stress is the result of a build-up of heat in the horse’s body, usually due to some impediment to the normal sweating process.  In the horse, sweating is the most important means of reducing core body temperature. It works because the water oozing out the sweat glands evaporates, thereby cooling the skin.

The transfer of blood to blood vessels and capillaries close to the skin (making them prominent and obvious) is another way the body cools the blood.

Circumstances which can lead to a horse becoming heat stressed include:

1. Cotton sheets are perfectly acceptable but leaving an inappropriate cover (eg synthetic) on your horse on a hot day is not. The poor thing has NO WAY of cooling down. The cover prevents evaporation so hot sweat accumulates on the skin and prevents the heat from dissipating. You have effectively left him in a sauna…………. How long would you be able to stand it? Sorry but there is no excuse, they are way better off without a cover in hot weather.

2. Well nourished horses don’t fade.

3. Cushing’s horses that haven’t shed their winter coat are in a similar predicament.

4. Exercise during hot weather that is too strenuous for the horse’s level of fitness.

Points 1-3 are compounded by poor nutritional status. Failure to feed sufficient salt on a daily basis leaves the horse vulnerable to electrolyte disturbances due to loss of precious salt in a heavy sweating episode. Feeding too much protein in the diet also generates more heat.

What are the signs of heat stress?

Various levels of distress, from loss of willingness to serious fatigue

• Elevated heart rate (i.e. above 60-80 beats per minute at rest).  Normally the heart rate should drop to 44-52 beats per minute within 15 minutes of ceasing exercise

• Elevated rectal temperature (above 41 degrees Celsius)

• Altered respiratory rate. Usually rapid (120-140 breaths per minute, normal respiration for an adult horse is 8-12 breaths per minute).

•  Agitation, staggering and potentially, seizure.

What to do?

Cease any exercise immediately and take urgent steps to cool the horse down. Find or create some shade and help cool the skin surface with water. Call your veterinarian as the longer his temperature stays elevated the more likely for complications to set in, including internal inflammation, muscle damage and even organ failure.

Take these steps in hot weather

1. Provide shade- do what it takes to make sure your horses have the option to get out of the sun.

2. Make sure your water troughs are full, clean and cool at all times by bucketing them out regularly.

3. Add salt to daily feeds, this will encourage more water consumption and set your horse up for exercise when he will lose salt in his sweat.

4. Hose them down. This will help lower body temperature and besides you can tell, it feels great! Some horses will race over to the sprinkler for a dowsing!

5.  Be mindful of the conditions when you choose to ride. It is not fair to exercise some horses in heat and humidity. Think morning or evening when it is cooler.

Anhydrosis is a serious condition whereby the horse does not sweat properly or at all and therefore cannot reduce his core body temperature. Signs include sweating in small patches in odd places and a very dry hair coat with loss of hair around their neck and shoulders. The exact cause has yet to be established. Possibilities include hypothyroidism, hypochloremia and exhaustion of sweat glands. Many of the symptoms point to the chronic lack of sodium and chloride (salt) and we have seen several cases respond very well to the addition of salt to the diet with these horses soon returning to normal sweating patterns.

By Jenny Patterson (Calm healthy horses)