Summer arrives with longer days, brilliant sunshine and weekends of memorable horse shows. But warmer weather doesn’t always mean smooth sailing in the realm of riding and horse care. Insects, high temperatures and humidity during the summer months require special precautions, which, depending on your horse, may require minor to significant changes in his management. To learn more about dealing with the challenges of summer, Dressage Today spoke with Dr. Emily Harrison, of southern New York, Dr. John Lockamy of Wellington, Florida, and Dr. Elaine Carpenter, based in Cave Creek, Arizona.
Ensuring that your horse has a happy and healthy summer begins with preparation. “Planning ahead and being generally proactive in your stable management can prevent a wide variety of equine health problems that arise during those hot summer days,” explains Dr. Harrison. As you may already know, there are a few steps you can take to maintain your horse’s overall health during the summer.
For starters, make sure that your horse is up to date on his regular vaccinations and deworming schedule. Entering the season healthy can help keep horses in top condition under the stress of heat and humidity. Making sure that your horse has plenty of water is obvious, but should not be taken lightly. In the summer months it is especially important to take note of how much water your horse regularly consumes. This can also help you to notice if he is drinking less water than usual.
Check to make sure that your barn has adequate airflow, as a well-ventilated barn is important not only for keeping horses cool, but also for keeping bugs at bay. Placing a horse-safe box fan outside your horse’s stall can be helpful to create additional circulation.
If you plan to haul your horse in a trailer during particularly hot times in the season, try to arrange your travel plans so that you are transporting him during the coolest parts of the day, such as early in the morning or later in the evening. To further ensure that your horse stays as comfortable as possible, you can body-clip him and protect him from the sun with a fly mask and fly sheet.
If your horse has pink skin on his face, you can also apply sunscreen to prevent sunburn. Ideally, if your horse is turned out, you should also try to provide adequate shade for him to get away from the sun, either in the form of trees or a run-in shed. Sometimes, however, horses with even the best care have difficulty tolerating the trials of summer heat and can suffer dermatologic conditions such as sweet itch or summer sores, or even lose their ability to sweat or tolerate extreme heat.
During the summer, horses may be at risk for heat stress, a condition Dr. Carpenter is very aware of in Arizona. “If your horse is not feeling well during hot weather, heat stress may be a factor,” she explains. Signs of heat stress can include lethargy, increased temperature, increased respiration, increased heart rate, abnormal sweating and, in extreme cases, muscle tremors and the horse going down on the ground.
A vet might find the horse anemic, with a lowered white blood-cell count. Heat stroke is an acute attack of heat stress, when the horse suddenly exhibits these signs, especially during intense exercise. Once a horse is in a situation where he is experiencing heat stress, his muscles can begin to break down. The muscles release an enzyme that can damage the kidneys if not properly managed. If the horse’s urine is red or brown a couple hours after heat stress symptoms are evident, test the kidneys for damage.
There are preventive steps you can take to protect your horse from heat stress. “Try to keep him in a cool environment,” Dr. Carpenter suggests. “In Arizona we use misting fans in the barn and the arena. We also suggest that riders exercise their horses in the early morning because it is the coolest part of the day.” Watch the horse carefully for signs of anhidrosis, the inability to sweat, because if the horse cannot thermoregulate, he is more susceptible to heat stress. Take the horse’s temperature if he is not acting himself.
“You can also monitor the temperature of horses that may be at risk during and after your ride,” Dr. Carpenter says. The normal temperature range is between 99–102.5 degrees Fahrenheit. You also will want to consider your horse’s physical condition and adjust your ride to give him plenty of breaks and assess the appropriate intensity of his workload. Overwork can lead to heat stress.
If you worry that your horse is overheating, spray him with water or sponge him with an alcohol bath to bring his temperature down. Involve your vet, who can administer IV fluids, which not only cool the horse but also flush the muscle enzymes that may collect in the kidneys. The vet may also use an ice-water enema or an alcohol bath to cool the horse quickly.
Some horses that live in areas of high heat and humidity can develop anhidrosis, according to Dr. Lockamy. This is a very serious condition, as it can lead to heat stress. “Anhidrosis happens when the sweat glands become refractory, or insensitive, to the presence of epinephrine,” Dr. Lockamy explains.
“When the horse gets hot, his body releases epinephrine, which triggers the sweat glands to release sweat, and as it evaporates, it cools the horse down.” In locations where the heat–humidity index remains constant during the day and overnight, the horse never gets a chance to cool off and there’s a continuous epinephrine release over a long period of time. “So what happens,” says Dr. Lockamy, “is the sweat glands get insensitive to the presence of the epinephrine so they function less or stop functioning completely.”
There are a few steps a horse owner can take to reduce the risk of the horse developing anhidrosis. “Focus on the ventilation in the barn,” Dr. Lockamy suggests. “Many horses are outside and turned out for a few hours, but the rest of the time they are in the stall box, so you want to make sure they have great ventilation in the barn, including fans that may need to be running constantly over the hot months.” Keeping the horse as cool as possible reduces the risk of refractory sweat glands.
If you notice that your horse is sweating less than normal, consult your veterinarian. There are steps your vet may recommend that can help the horse regain sweating function:
• Always check the thyroid function on a horse that you suspect might be having trouble thermoregulating. There is a blood test that your veterinarian can administer called the blood serum thyroid assay test. The thyroid gland is the most sensitive gland in the body and if its function is low, the horse may have trouble sweating.
• Don’t be excessive with electrolyte use. A University of Florida study demonstrated that increased electrolytes do not improve sweat function, so feed the recommended amount of electrolyte supplement.
• Bring a bucket with a little bit of rubbing alcohol mixed with water and a sponge to the arena so that in the middle of a ride you can wet the insides of the horse’s legs, where the blood vessels are close to the surface, the flank and the neck to help the horse cool off. The rubbing alcohol will help the water evaporate more quickly.
• Give the horse a can of beer in the morning and at night in his feed. Beer is an old horseman’s remedy, but it can help improve sweating function because it is theorized that the yeast cultures prompt the horse to sweat.
• There are products on the market that might help horses sweat, including a complex of Chinese herbs that sometimes help. Even though the use of Chinese herbs is less conventional, some horse owners might prefer this approach over the use of drugs and other medications. Dr. Lockamy has had particular success with a product called New Xiang Ru San, a Chinese herbal supplement.
• For horses that still don’t sweat, Dr. Lockamy recommends a low dose of clenbuterol in the morning. Clenbuterol is a bronchodilator, but the side effect of the drug is sweating. “It’s not an ideal drug because it is tough on the cardiac system, but we use a very low dosage to help get through the summer for problematic horses,” he says.
One of the more prevalent health problems that Dr. Harrison sees during warmer weather is insect-bite hypersensitivity, commonly known as sweet itch or summer eczema. Dr. Harrison explains that a hypersensitivity reaction is most often found on the belly, face, base of the tail and along the base of the mane.
It appears as a crusty skin lesion that may be weeping serum and is red from repeated irritation. In more severe cases, she explains, there may be large patches of hairless skin. You may see your horse repeatedly try to scratch himself on objects in the barn or field.
Sweet itch is caused by the horse’s allergic reaction to the saliva of culicoides, or biting midges, which causes intense itching that can severely damage the skin.
This problem is generally seen when temperatures are compatible with the midge fly’s larvae hatching. “Prevention and proactive management are key aspects to limiting the effects of the allergic response,” Dr. Harrison advises.
To protect the horse from biting midges, she suggests you apply these management tactics:
• Use a full-face fly mask and well-fitted fly sheet that wraps under the horse’s belly and protects the neck. These sheets are lightweight so they do not overheat the horse.
• Fly sprays can help keep midges off the horses but be aware that the repellant effect is often short-lived.
• Avoid turnout at dawn and dusk because biting midges are most active at these times. You can also switch to night turnout.
• When possible, turn horses out together because they will often stand nose to tail in an effort to swish insects away from each other.
• Use ceiling fans and stall-side fans to promote air circulation.
• Pick pastures and maintain clean stalls. Insects breed in manure.
• Keep horses out of paddocks with areas of stagnant water—a feeding ground for flies and other insects.
Once you have identified a horse with sweet itch based on the clinical signs, involve your veterinarian. Treatment may include antihistamines or steroids. Allergy shots can help desensitize some horses but the effects aren’t usually seen until the following summer season.
Protecting your horse from flying insects by taking the above precautions can also reduce the occurrence of summer sores, according to Dr. Lockamy. They are most common in tropical or temperate climates and appear as open, inflamed, itchy sores on the lower legs, lips, ears and other moist areas of the body. They are caused by the larvae of the Habronema or Draschia worms, which live in the horse’s stomach and reproduce by sending their eggs out into the environment through the horse’s manure.
The larvae are incubated and carried by stable flies in the manure, after which time they usually complete their life cycle when they re-enter the horse. However, sometimes a fly will deposit the larvae onto a scratch or break in the horse’s skin, which causes the summer sore.
If you suspect your horse has a summer sore, call your veterinarian. He or she may recommend a larvicidal treatment such as ivermectin, an antimicrobial to prevent secondary infection and an anti-inflammatory such as a corticosteroid to reduce inflammation and itching.
An untreated summer sore not only can become incredibly itchy and uncomfortable for the horse, but can also develop a large amount of proud flesh, which can require minor surgery to remove.
With these strategies at hand to help combat the stresses of summer, your training sessions might be more productive than you had imagined.