Caring for Horses During Hot Weather

Livestock Update, August 2007

Dr. Shea Porr, Northern District Equine Extension Agent cporr@vt.edu or 540-687-3521 ext 27

Summer is here.  Temperatures reaching the middle to upper 90’s in July should convince anyone of that.  Here are several management factors that should be carefully considered when managing horses in hot, summer weather.

Plenty of water should be offered to the horse.  The average 1000 pound horse will drink around 10 gallons of water a day.  Working horses, particularly in the heat, can easily increase this to 20 or more gallons a day.  Water and electrolytes are both lost when a horse sweats, leading to potential problems with dehydration and other metabolic conditions if they’re not replaced.  Make sure the horse has access to clean, fresh water and salt at all times.  Be cautious adding flavorings to water.  While it may encourage some horses to drink, some of the products contain salt which may cause the horse to stop drinking if too much is added.

Exercise during the hot hours of the day should be limited.  Exercise generates body heat which must be released to prevent overheating.  This can be difficult during summer months.  The Heat Stress Index, or “Misery Index”, can help people to know when to be cautious about working with horses during hot weather.  If the combined temperature and humidity are over 150, care should be taken to ensure the horse does not become heat stressed.  If the humidity is over 75%, sweating as a cooling mechanism becomes compromised.  The sweat doesn’t evaporate off the horse; it runs off them, which is much less efficient.  Sweat losses in a working horse can increase from 20-300% in extreme conditions.  If the horse must be worked during the heat of the day (perhaps you’re at a show or competition), then care should be taken to ensure the horse has adequate shade and ventilation (fans or misters) to help them stay cool.  Between classes, stand them in front of a fan in the shade or sponge them off and scrape the excess water from them to help cool them down.  Again, water and salt should be offered frequently.

Overweight horses will have a harder time dealing with the heat.  The added body fat acts as insulation, trapping body heat and making it more difficult for the horse to cool off.  Working an overweight horse in the heat is an excellent way to end up with a sick animal.

Feeding management is also affected by the temperature.  Some horses will go off feed if they get too hot.  This can be a problem if the horse is too thin or is losing weight due to the heat – they can’t gain if they don’t eat.  Also, the digestion of feed results in the generation of body heat, and some feeds generate more heat than others.  Adding fat to the diet will increase the calories in the feed without increasing the volume of feed and fat burns cooler in the body than protein or carbohydrates.  Feed only as much protein as the horse needs in order to reduce the heat load.  Also, feeding grass forages will decrease the metabolic heat generated as compared to feeding legume forage.

Barns should be opened as much as possible to allow any breezes to keep the stable ventilated.  If necessary, add fans at strategic locations to pull air through the barn.

Cooler weather will return, never fear!  In the meantime, keep plenty of water and salt in front of the horses, don’t exercise them during the heat of the day, and feed them appropriately for their needs.  For more information on managing horses, contact your local Virginia Cooperative Extension Office.

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