When you’re training toward a goal, consistency is important, but be mindful when you ride to avoid overheating—or worse. For practical advice on summer riding, we turned to veterinarians in two hot—but very different—regions, the Southeast and Southwest.

Hot and Dry

Summer temps in the desert Southwest can easily climb to 120° Fahrenheit, so riding between mid-morning and late afternoon is strongly discouraged.

“Ride early and be done by 10 a.m. or break it into two sessions,” advises Christine Staten, DVM, a large animal veterinarian and owner of Adobe Veterinary Center in Tucson, Ariz. “[You can] ride early in the morning and late in the day, instead of one long session.”

In addition to shorter rides, don’t hesitate to head for the shade for quick breaks.

“In dry environments, just getting under shade can reduce the temperature by 20 degrees,” she notes.

“This advice is as much for riders as it is for horses,” says Staten. “We see more heatstroke in riders in the middle of a hot day than in horses. Every year in Tucson, we have people die from heatstroke on the trail.”

Hot and Humid

Heat and humidity alone can be challenging for horses. Add exercise to the equation and health risks increase.

“The coastal humidity in Florida multiplies the heat index substantially because it reduces the body’s ability to dissipate heat through evaporation or sweating,” explains Caitlyn Henderson, DVM, of Peterson Smith Equine Hospital in Ocala, one of Florida’s largest equine clinics. “It’s akin to trying to breathe and cool yourself from under a hot, wet blanket.”

In addition to not riding during midday, Henderson always advises having a shaded area where horse and rider can take short breaks. Keep buckets of cool water available so the horse can drink. When humidity climbs, it helps to add a misting fan if the area has access to electricity.

Quick Math

For a simple assessment on riding safety, add the air temperature to the humidity percentage.

When the combined total is under 130, a healthy horse can effectively cool himself. When the combined total is between 130 to 150, the horse’s ability to cool himself is decreased.

If the combined total is over 150, this ability is greatly reduced. Once the combined total is over 180, conditions can be life threatening for any horse under physical stress.

A good rule of thumb is to avoid riding if the air temperature and humidity combined total over 150.

Horses at Risk of Overheating

Certain horses are more vulnerable to overheating. These include:

• Old or very young
• Not acclimated to climate
• Out of condition
• Heavily-muscled, thicker body types
• Diagnosed with an endocrine disease, like PPID (Cushing’s disease)
• History of equine asthma
• Recovering from a recent respiratory challenge
• Diagnosed with anhidrosis (partial or total inability to sweat)

“If your horse shows any signs of heat stress, have your veterinarian evaluate him to determine if there are underlying issues,” says Staten. “If this is happening, there’s probably something going on that needs to be addressed so we can come up with a plan to remedy it.”

Acclimation

Whether you live in a hot, arid region or where it’s hot and humid, it’s critical that your horse be acclimated to those conditions before strenuous exercise.

After 25 years of equine practice in Tucson, Staten has never seen a healthy, acclimated horse have heatstroke. The problems she sees are in horses that have recently moved to the area or have an endocrine disease, like PPID, or have anhidrosis.

Staten finds the best season to move a horse to the desert Southwest is fall or winter, as this gives the most time to acclimate. If you move in spring, expect acclimation to take at least a couple of months.

“Dark-colored horses struggle more when trying to acclimate to our weather. If a horse is still shedding a winter coat in spring, that can make it rough on them,” she cautions.

“It’s recommended that human athletes take six weeks, minimum, to acclimate to a new climate, and no less than that should be afforded to our equine athletes,” says Henderson.

She finds it easier for horses to gradually acclimate to heat and humidity if they’re introduced to it in early spring, at latest.

Proceed with caution if you’ve just moved to an area where it’s significantly hotter and more humid than where your horse lived previously.

“I see a lot of riders who come here from New York and New Jersey and just want to ride, but to do this in the summer months is going to be more of a challenge,” says Henderson.

She recommends giving the horse a full week to recover from travel. Then return to light work under saddle, exercising at the coolest time of the day for at least six weeks as the horse acclimates.

She encourages riders to take it day by day, because some horses need more time than others to adjust.

Keep Horses Drinking When It’s Hot

Hydration is critical for horses in hot weather.

Electrolyte loss due to exercise or simply sweating can lead to metabolic stress and decrease the horse’s thirst response, which can result in dehydration and overheating.

In addition to access to salt (plain or trace mineral), horses may need electrolyte supplementation to replenish the sodium, potassium, calcium, and chloride lost through sweating and urination.

Henderson tells riders to prepare for summer temps by introducing electrolytes to the horse’s diet earlier in the year. The goal is to encourage water intake year-round, so horses are always well hydrated before exercising.

“If you’re at a show, offer water between classes,” says Staten. “If you’re on the trail and there’s a place to drink, let them. A horse should always be allowed to drink, even when he’s hot.”

Cool Down

Many people think the best way to cool a hot horse after exercise is just to walk him in the shade. However, research shows that the most efficient method is to continuously shower a stationary horse with cool (79° Fahrenheit) tap water. In a recent study, this method decreased the horse’s core temperature in an average of just two minutes.

“Focus water on the jugular vein and the large veins inside the legs,” says Staten, noting that this helps cool the horse’s core temperature.

Finish cooling out by slowly walking the horse until his respiratory rate and body temperature are normal. Movement helps remove lactic acid from the system and keeps muscles from tightening up.

Always allow the horse to drink during recovery. Research shows that horses voluntarily drink more within the first hour after exercise when water is about 68° Fahrenheit.

Offer half a gallon of water at a time throughout the cool-down process until the horse doesn’t want to drink any more. Make sure there is plenty of water in his stall/corral to drink after he’s totally cooled out.

Summer Travel

Any time you trailer during the summer, pick the coolest part of the day to travel. Increase air flow by opening all vents and windows, but for safety’s sake, do not let horses put their heads outside the trailer.

“Hot metal is like an oven, so get them out of the trailer as soon as you get where you’re going,” says Staten.

Common Sense

So, is it ever too hot to ride?

“If you think you are going to struggle to get through a ride due to the heat, so will your horse,” says Henderson. “If there’s ever a time you think it might just be too hot to ride, you’re probably right. Go with your gut feeling and take your horse’s health into consideration. It’s never wrong to delay a ride for a cooler time of day for the safety of your horse.”

This article about when it may be too hot to ride a horse appeared in the July 2024 issue of Horse Illustrated magazine. Click here to subscribe!

The post How Hot is Too Hot to Ride? appeared first on Horse Illustrated Magazine.

Below, we’ll examine what heat stress looks like, the warning signs, what to do if your horse overheats, and how to prevent dehydration from heat stress.

What Causes Heat Stress in Horses?

Horses primarily create heat while digesting their feed and during any activity that requires their muscles to work. Even light activity in extremely hot, humid weather could cause your horse to overheat.

You may notice that your horse’s blood vessels appear larger and distended when it’s hot outside. This reaction is normal, as it shunts the blood to the skin to rid the body of excess heat; however, this doesn’t provide adequate cooling if the air temperature is warmer than the horse’s body temperature.

Other than humans, horses are the only mammals that sweat. During hotter conditions, they primarily use this mechanism to wet the body and allow cooling via evaporation. The problem occurs when the sweat doesn’t evaporate to allow adequate cooling, potentially leading to heat stress.

“Horses are pretty efficient at dissipating heat compared to species that don’t sweat,” says Kris Hiney, Ph.D., associate professor and Equine Extension Specialist at Oklahoma State University. “But they can still get heat stress [during] prolonged periods of high temperatures or working in high temperatures. Very young or infirm horses are more likely to suffer from heat stress.”

Detecting Heat Stress

Hot skin and profuse sweating or less sweating than expected for the activity could be warning signs of heat stress. Hiney advises looking for high body temperature, an elevated heart rate, and a respiration rate beyond what’s expected for the workload.

“Working in hot temperatures may not be completely avoidable,” she says. “[But] it’s important to recognize the signs that your horse may be overheating.”

Hiney recommends practicing the following techniques ahead of time so both you and your horse will be familiar with them when needed.

◆ Use a rectal thermometer (keep one with you if you’re far from a barn) to monitor heat load. Body temperature will normally increase with exercise, and body temperatures of 104 degrees to 106 degrees Fahrenheit are common for some events.

However, horses with these body temperatures need to be cooled carefully. If a horse’s temperature is over 106 degrees, take immediate action to cool the horse. Temperatures reaching 107 degrees may require veterinary assistance.

◆ Check your horse’s heart rate, either with a stethoscope or manually. When the horse is allowed to rest, his heart rate should noticeably begin to drop. It should return to 40 to 50 beats per minute within 15 minutes. Failure of the heart rate to drop quickly indicates heat stress.

“Flared nostrils and heaving flanks while breathing are not only from work, but also from the increased heat load,” Hiney explains. “Allow the horse to rest and watch carefully for a reduction in breathing rate and intensity.”

◆ Assess the amount and location of sweat. Normal sweating patterns include along the neck, flanks and between the hind legs. With intense exercise or extreme temperatures, the horse may be completely covered in sweat and will need help being cooled.

A horse that has ceased sweating is most likely suffering from heat exhaustion and is in critical need of care.

How to Treat Heat Stress

If you suspect your horse is overheating, it’s vital to stop exercising and move him to a cooler setting right away. You will likely need to help him cool down to prevent heat stress from turning into heat stroke, which can have dire consequences.

“Evaporation through sweat is the major way horses dissipate heat, but high humidity levels will limit the effectiveness of sweating,” says Hiney. “Increase airflow to the skin by removing all tack and equipment and use a sweat scraper to remove excess sweat.

“Cool running water can greatly aid in cooling,” she continues. “Apply water or even ice along major blood vessels like the neck, chest and inside of the legs. Blood will cool as it passes through these areas and then return to the trunk of the body to help dissipate the heat load. Continual application of cool, running water will prevent the warming of the water on the horse’s skin. Otherwise, use a scraper to remove the warm water and increase the rate of cooling. Water left on the skin will warm rapidly and trap heat against the horse’s body.”

Hiney says that you can still help your horse cool down even when you don’t have access to running water by using a sponge to wet the major blood vessels. Again, you should concentrate on the neck and chest. She also suggests adding rubbing alcohol to the water to increase evaporation and aid in cooling.

If you need to cool your horse while riding if you’re not near running water, Hiney suggests using a squirt bottle to apply cool water along the major exposed blood vessels in the neck and chest. You can refill your water bottle from streams, lakes or stock tanks.

“Air movement is another major way that animals lose heat,” she says. “Supplying fans or keeping the horse in a breezy area is ideal. Fans with higher velocities provide more effective cooling. If you have access to electricity, put a fan near the arena to aid in cooling during rest periods. This fan can greatly assist with continuing normal training during the summer. Even so, be sure that the horse’s heart rate and respiration rate have dropped before returning to work.

“Simple strategies like keeping the horse in the shade or riding in shaded areas prevent heat gain directly from the sun,” Hiney adds. “Standing under trees is even more useful, as the horse will radiate heat up to the leaves, which are continually cooled by their own evaporation.”

She warns that heat stress can quickly turn to heat stroke. If you feel this is happening, cease work, strip tack off the horse, and get him into the shade immediately. When facing heat stroke, veterinary care with IV fluids may be necessary.

Heat Index

Through appropriate management, heat stress can be prevented. Start by paying attention to the heat index in your area to understand when it’s dangerous to work your horse. Although different horses may tolerate heat differently, follow general guidelines to ensure you’re not putting your horse in danger.

“Pay attention to heat and humidity,” Hiney advises. “A good rule of thumb is to add the values of the temperature [in degrees Fahrenheit] and humidity [relative percentage] to get the horse’s comfort index. Horses cool themselves normally—unless dehydrated or fatigued—if the combined values are below 130.

“If the combined temperature and humidity is over 150 (such as 90 degrees Fahrenheit with 60 percent humidity), horses will need assistance in cooling,” she continues. “If temperatures and humidity are expected to reach 170, it may be best to plan early morning riding or skip intense work. Even riding in the evening may not see a large drop in temperature until the sun has been down for several hours.”

Dangerous Dehydration

High heat or excessive sweating can cause dehydration in horses. If your horse doesn’t replace the fluid lost during sweating by drinking adequate water, he can become dehydrated, which can be life-threatening.

“Horses can become dehydrated in as little as two to three hours under the right conditions,” says Hiney. “Horses need to be well-hydrated before beginning to work, for example, horses that have come off of a long trailer ride.”

She explains that some warning signs of dehydration include prolonged capillary refill time (checked by pressing your finger into the horse’s gums) and tenting when skin is pulled from the neck or over the eye. The horse may also have a gaunt or tucked-up appearance.

Colic and overheating are possible, but if the horse gets an electrolyte imbalance due to dehydration, tying up and even death could occur.

“The primary mechanism horses use to dissipate heat is through sweating,” says Hiney. “Sweating leads to dehydration if the horse isn’t allowed to replenish, and the rate of sweating can outstrip the ability to keep up.

“Warm body temperatures encourage horses to drink, so allow access to water in the cool-down period,” she continues. “Allow frequent sips of cool water. Saline can also help replenish water and electrolytes, but be sure to have plain water available, too.”

Key Takeaway

Luckily, horses usually bounce back after a bout of heat stress or dehydration without any lasting effects. However, both can become very serious conditions in a relatively short span and, if left untreated, can lead to death.

It’s best for your horse’s health to not allow either to begin with by ensuring he always has access to clean, fresh water and avoiding exercise in extremely hot weather.

Ride in the morning when it’s coolest, and reduce ride time and intensity when it’s hot and humid, or refrain altogether if the temperature and humidity are above safe levels.

This article about heat stress appeared in the July 2023 issue of Horse Illustrated magazine. Click here to subscribe!

The post Heat Stress in Horses appeared first on Horse Illustrated Magazine.