Managing horses during hot weather

BY Krishona Martinson, PhD, Marcia Hathaway, PhD and Christie Ward, DVM University of Minnesota Roy Johnson, MS Cargill Animal Nutrition
Farm Forum

Summer has officially arrived in Minnesota bringing the challenge of managing horses during hot weather. Fortunately, research has shown that horses can acclimate to hot and humid environments. A 15- to 21-day acclimation period is recommended for horses originating from cooler or drier climates that are traveling to compete or reside in hot, humid conditions. The acclimation period results in an increased tolerance to both heat and exercise. However, acclimation does not reduce the need for close monitoring of horses during training and competition in hot and humid environments.

To help reduce the effects of heat and keep horses comfortable:

• Provide turnout during cooler times of the day (early in the morning, late at night, or overnight).

• Provide relief from the sun through access to shade from trees or buildings. Shade will change throughout the day and constructed buildings may block natural air flow.

• Watch for signs of sunburn, especially on white or light-colored areas; use masks and ensure access to shade.

• Fans help to improve airflow; be sure to keep cords and plugs out of the horses reach to prevent electrocution.

• Ensure access to clean, cool (recommended temperature range of 45 to 64°F) water at all times. Depending on feed, an adult horse in a cool climate will normally drink 6 to 10 gallons of water each day while at rest, and much more while working or in hot conditions.

• Water buckets and tanks may need to be cleaned more regularly in hot weather as algae and bacteria grow rapidly in warm water. Blue algae toxicity (which affects horses, pets, and other livestock) is more common in ponds or slow running streams during hot, dry weather.

• Free choice access to salt will encourage drinking. Loose salt is preferred over a salt block.

• Consider providing electrolytes to horses that have been sweating heavily or are expected to do so. If electrolytes are added to drinking water, also offer plain water since some horses dislike the taste of electrolytes and will drink less. Only use electrolytes that are formulated for horses.

• Reduce riding intensity and length; heat stress can affect any horse but is especially common in older, obese and out of condition horses. Young foals also tend to be more prone to heat stress and dehydration.

• Clip horses with long hair coats (i.e. horses with Cushing’s disease) to enhance cooling.

• Transport horses during the coolest part of the day. Ensure that trailers are well ventilated and offer water frequently. Do not park in direct sunlight with horses inside.

• Horses with anhidrosis have little or no ability to produce sweat; these horses are prime candidates for heat stress.

It is recommended to avoid riding a horse when the combined temperature (°F) and relative humidity (%) surpass 150. If a horse must be ridden during hot and humid weather, or you live in an area where hot and humid weather is prevalent, it is essential to:

• Adjust your schedule (ride early in the morning or late at night).

• Keep the work light and include frequent breaks that allow the horse to cool down and regain a normal respiratory rate. Do not work the horse beyond its fitness level.

• Watch for normal sweating.

• Create airflow (use fans) and work the horse in shade when possible.

• Provide access to cool, clean water at all times and offer water frequently during work. There is no reason to withhold water from a hot horse.

• Call a veterinarian immediately if your horse stops producing sweat, breathes heavily, or becomes lethargic, distressed or uncoordinated.