Horse Care in Hot Weather

By Bonnie J. Hilton

Saddle and Bridle Magazine Equine Articles


Crane logo What care do horses need during very hot weather? Written for Saddle & Bridle magazine by Bonnie J. Hilton. © copyrighted horse article.
I thought I knew at least some of the facts about sun stroke, heat stroke and heat exhaustion. One of my aging equines had some problems develop during a very hot and humid summer, and causes of such were not easy to define. Then I thought it would be a good idea to get some clarity on this subject for readers who see something going on with their equine but can't put a definite finger on just what is happening I also want to bolster the argument behind feeding electrolytes, which for some horses, young and old, in some conditions, should be a major consideration.

Some people will think that the symptoms caused by heat and humidity relate to horses with azoturia. (Paralytic myoglobinuria or exertional myopathy also known in mild versions as "tying up") Not necessarily so. There is a condition well known to educated endurance and performance riders as endurance related myopathy. It is very similar to a mild case of tying up. The horse may exhibit muscle cramps, tremors and stiffness and be unwilling or unable to move. This condition is not azoturia at the cell level. Endurance related myopathy is due to energy depletion and is not an energy (glycogen) storage problem. Simply put, due to a long period of exertion, the muscle energy stores are depleted and the resulting metabolic changes going on cause the lactic acid build up in the blood. It doesn't take a rocket scientist to realize that this condition could be more critical during times of excessive heat and humidity for the older horse.

Keeping up energy stores in older equine muscles is not something I have been concerned about, but I just had a wake up call. Make sure you are feeding enough and what you are feeding is supplemented with what is recommended for your area, depending on forage conditions. A drop of only a few pounds with the older equine can put them in a downward spiral in a short time during periods of environmental stress.

The aged equine that started this research had lost weight in muscle. It had happened quickly and I believe it was the underlying reason for the performance problems. The reason for the loss was a combination of not paying attention to forage growth in turn out (growth recovery), which was being depleted by the weather conditions and no subsequent increase in concentrates to balance the energy needs. I should add that hay quality was poor at times and this probably added to the combination of conditions. Obviously, if we need to take this much precaution with the older equine that may or may not be in daily work, we need to be more vigilant with the younger equines who have a much higher risk being in heavy work.

Reading in some of my equine care publications I noted the following statements. "A horse on a long physically depleting ride needs an average of one gallon of water per hour." "Sodium chloride, potassium bicarbonate, calcium and magnesium, are lost in the sweat and urine in proportion to the severity of the stress, temperature and humidity and the individual sweating characteristics of the horse." "To compensate for these losses, in addition to giving the equine plenty of water, it is a good practice to give an electrolyte solution, even though it may not be needed by all horses." "It will not harm the horse as long as water is available and the horse is allowed to drink as much as it wants during rest periods."

The aged gelding who caused me to go into research about possible causes has shown marked improvement since being put on electrolytes. For those readers who are thinking it already, yes, he did have a salt lick, but like many horses, he was not using it enough to compensate for what he was losing in sweat. As his muscle stores got more depleted and he got more lethargic. A caution that must be emphasized is that if you put the horse on electrolytes, make sure they have plenty of plain water to drink as well. The one bucket in the stall may not be enough, make sure you monitor intake, if you possibly can.

Heat exhaustion comes first, in most cases, followed by heat stroke. Abnormally high body temperature, which is known as hyperthermia, is recognized as heat stroke in humans and is classed for both heat exhaustion and heat stroke in equines. Heat exhaustion's first major symptom in humans is fatigue, followed by faintness, dizziness, nausea, restlessness, headache and when sweating is profuse causing heavy salt loss, heat cramps in the arms, legs, back or abdomen. Now lets face it, the horse won't tell us it is dizzy or has a headache and we only notice the lack of energy and maybe, like me, the stiffness, which was not the same as the daily complaint of old age. The nausea may or may not manifest itself into colic and then we have the major problem of laminitis on our hands.

We all know that on a hot, humid day, the body temperature will be higher. The problem is that we may not be taking enough precaution for the sweating issue, even for a horse that is just standing around in a paddock, fighting off flies. Horses can develop sweating problems, most notably the partial or complete ability to sweat in response to increased body temperature brought on by climate or exercise. It is referred to as anhidrosis and readers need to keep that little word tucked away in the recesses of the brain. For some horses a drastic change in climate seems to bring on the problem.

With gradual onset, that we may not notice, the equine will exhibit poor exercise tolerance, loss of weight and condition, a dry rough hair coat and patchy hairloss over the face. I have seen this with one older horse and never realized, until now, that they were probably not sweating enough and that was the reason that they seemed so out of shape.

With dry lot shadeless paddocks, heat stroke does happen. It can happen to conscientious owners, that just didn't know better, at the time. The signs are; weakness, rapid breathing, heavy sweating, elevated temperatures to 105 and above, and eventual collapse. Call the veterinarian and get the horse in out of the sun or provide some sort of shelter and start getting the temperature down with cool or lukewarm water. Don't spray cold water on the animal because that can induce shock.

In horses shock is defined as, "Failure of the circulatory system, which can be caused by severe loss of blood, severe trauma, or other serious conditions, of which one is hyperthermia (high body temperature). Regardless of the initiating cause, once shock begins, circulatory inadequacy is the inevitable result. Because of circulatory deficiency, irreversible shock leads to cellular death in the vital organs due to tissue hypoxia (lack of oxygen)."

What are some of the husbandry, as well as training changes, that could be made?

1. Water should always be your first priority. I was told that you can assume that for every 100 lbs. of weight, a horse will need one gallon of water a day, as long as exercise or environment doesn't increase demands. For a 1000 lb. horse we are talking a minimum of 10 gallons of water. It should be available at all times and it should be clean and as fresh as possible.

2. Make shade available. Keeping horses stalled during the day and out at night is a common practice where cooler nighttime temperatures are common However, stalled indoors in a stifling hot building, with poor air quality, can be worse than being outside. You have to have air flow, thus the reason for fan use. Shade sheds, ("horse ports") like I have seen down south and out west are common in dry lot and open field situations, but in a small herd situation, the shade shed has to be big enough to accommodate all the members of the herd comfortably. Injury due to space competition has to be a consideration in building any type of shelter.

3. Changing the training schedule (and feeding schedule) -- working early or late when it is cooler is smart. A horse or human that sweats will stay cooler as long as that sweat dissipates, but when the air is what we call "heavy" and you are dripping wet just walking to the barn, it isn't healthy to even be thinking about exercising either yourself or your horse.

You need to keep the dew point and humidity level in mind. "The dew point refers to that temperature at which dew starts to form or vapor condenses to liquid. Humidity refers to the amount of moisture in the air. Percent humidity is a comparison to the maximum amount the air could contain at the same temperature.") Since I like to keep it simple, just remember that if the numbers are all high; high temp., high humidity and high dew point you will hear another term called heat index being used. It means it is going to be a dangerous environmental time for humans and animals.

4. Alter the diet. Cut the diet if you cut the work! If you have fit horses in a heavy six day training routine and you have to stop work for several days because of weather conditions, you need to change your equine's diet to protect it from the possible side effects of energy overload. I know that I am writing in far from scientific terms, but it is simple old horsemanship sense. Cut the work, cut the concentrates accordingly, but don't cut down the amount of hay being fed, if anything, increase the amount and the quality of the hay if you can especially if there is little or no growth recovery going on in your pastures. When the equine is brought back into work, the concentrates can be brought back up gradually to the previous amount.

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