By Tony Hawkins, DVM, Valley Vet Supply Technical Service Veterinarian  

Horses are very proficient sweaters, making them some of the most efficient animals at cooling themselves — but they are still at risk for heat stress. There are many ways we can help them sidestep this risk as the temperatures heat up. Below, I’ll cover diminished electrolytes, groups of horses at greater risk, signs of heat stress, and tips to keep your horses safe.  

Depleted Electrolytes Through Sweating  

Sweating is one of the most efficient ways that animals can cool down, and a horse can sweat up to two to four gallons per hour, which is remarkable. It’s important to note that horses will lose a lot of electrolytes while sweating, and they can experience electrolyte imbalances as a result. Even if horses are not in training or being worked, incorporating electrolytes into their diet will replenish those that are lost, encourage more water intake, and help prevent dehydration.  

I encourage horse owners to add electrolytes to the horse’s feed, rather than their water, which can make the water taste kind of salty or simply just different from what the horse is used to and result in lower water consumption. When added to the feed, the horse will benefit by consuming the electrolyte and then drinking the fresh water.  

Groups of Horses at Greater Risk  

Some groups of horses are at increased risk for overheating. These include horses that are overweight, in poor condition, or senior. Also at risk are horses that move or are transported from a cooler climate into a hot climate. If these horses are not given time to acclimate (for example, kept in a cool barn with constant fans), their risk increases.  

Also at risk are horses with conditions such as PPID (pituitary pars intermedia dysfunction), known as Cushing’s Disease — the most common hormonal disorder affecting horses and ponies. A PPID horse will often have a thick, non-shedding hair coat. These horses should be clipped during the warmer months to keep their hair coat short.  

Related: How to Get Ticked Off! Horses and Ticks

Know the Signs of Heat Stress in Horses  

• Visible signs — Watch for muscle stiffness, lethargy, stumbling, and incoordination.  
• Sweating stops — If the horse stops sweating, it’s a sign he’s getting overheated. Stop exercising and get him cooled down right away. 
• Elevated rate of respiration — Normal respiration is 8 to 18 breaths per minute, so if the horse’s respiration gets over 50 per minute it’s very concerning. 
• High temperature — A temperature higher than 39 degrees C (102 degrees F) is a sign of overheating. The normal range is 37.5 – 38.5 degrees C (99 – 101 degrees F).    

Photo: iStock/Sheikoevgeniya

Tips for Keeping Horses Safe  

• Offer the horse continuous access to fresh water and feed electrolytes (or use an electrolyte patch such as Equiwinner).  
• Understand the horse heat index to help determine if it’s safe to exercise your horse. Simply add the day’s temperature in Fahrenheit plus the percentage of humidity. For example, if it’s 80 degrees F outside with 60 percent humidity, the horse heat index is 140. A horse heat index in the 120 to 150 range is okay to exercise in. From 150 to 180, there’s a higher risk; light exercise may be allowed, depending on your horse’s acclimation and fitness level. If the horse heat index is over 180, avoid exercising the horse because the risk is too great unless the horse is an elite athlete. To avoid heat stress, stay on the safe side by riding during a lower horse heat index. 
• In warmer weather, horses need frequent breaks, water, and cooling down.
• Evaluate your horse’s body score and condition. If the horse is obese, thin, or has not been in regular work, begin with slow short workouts and very gradually increase time and intensity to allow the horse to acclimate to the heat and humidity.
• Be smart about when and where you ride. Avoid the hottest part of the day by riding in the early morning or later evening. Ride in shade or in a covered or indoor arena with good air circulation, along the edges of fields that have tall trees for shade, or along shady trails.
• Be smart about when you haul. Trailer during the cool early mornings, evenings, or overnight. Keep all windows and vents open to get as much airflow through the trailer as possible. Adequate shavings and mats will create a barrier between the hot road and the horse. 
• During a long trailer ride, stop at least every four hours. Get your horse out of the trailer for 20 to 30 minutes and offer access to fresh water, maybe even a small meal. Walk the horse and make sure he’s cooled off. If you need to, hose him down. 
• Schedule feeding around the horse’s training schedule. Horses produce a lot of heat through digestion. Because of this, we should avoid combining the added heat being produced through muscular activity, exercise, and digestion.
• Feed three to four hours prior to exercise or wait at least two hours after exercise to feed the horse. 
• Install a fan in the horse’s stall. Stalls can get very hot if closed up so a fan in every stall will improve air movement. As an added benefit, moving air from a livestock fan will help keep the flies and mosquitoes away. 
• Leave barn windows and doors open to increase ventilation and air movement as much as possible. 
• If the horses are out on pasture, shade from a tree or simple lean-to will keep them out of the sunshine. 
• To protect horses from sunburn and some of the resulting cancers that can develop, look into fly sheets or masks that can provide up to 90 percent UV protection. This is especially important for light-coloured horses and Paints, which can be more prone to sunburns. 
• If the horse is exercised the cooldown is important. Walk the horse for 10 to 15 minutes. After that, let him drink a small amount of water. The horse’s muscles accumulate a lot of heat during training, so if exercise stops without a cooldown that heat becomes trapped in the muscles. Sweating cools the skin surface, and during the cooldown blood is kept flowing so that cool blood can be transported back to the muscles to cool them off. 
• The American Association of Equine Practitioners recommends applying cool water to the entire horse, stating, “Spend time hosing his largest muscle areas and the largest and closest-to-the-surface blood vessels, the jugular vein in the neck, and the saphenous vein on the inner thigh. Doing this cools the body faster.”  

I hope this information will help you keep your horses safe, as we round out the warmest months of the year. Horse owners, please don’t forget to stay hydrated and cool yourself!

Related: When the Rider is Hot, the Horse is Hotter

Photo: iStock/WilshireImages