While summer gifts us with more daylight hours to ride and spend time with our horses, it also brings hoards of biting and disease-carrying bugs, as well as brutal heat and humidity—all of which can pose major health risks to your horse.

Flies not only bite and pester our equine partners, but they can also spread diseases like pigeon fever, vesicular stomatitis, equine infectious anemia and influenza. Additionally, they can trigger allergies, dermatitis and eye ailments, and constant stomping can contribute to joint issues and other impact-related injuries and even weight loss. While intense heat and humidity can lead to overheating, heatstroke and dehydration which can cause poor performance, lethargy, colic, kidney damage, collapse and even death.

To protect your horse from menacing insects and intense heat and ensure he stays happy, healthy and performing his best throughout the summer, follow these savvy management tactics and veterinary advice.

SMART FLY CONTROL

Unfortunately, flies are a part of managing horses, and you’re not going to be able to eliminate them all. But there are several effective management strategies and fly-control measures you can utilize to minimize their impact on your horse.

Management: First Line of Defense

Keeping areas clean and dry is one tactic to help manage flies. Flies are drawn to wet areas, where they drink and breed. Eliminate standing water in low-pasture areas and any containers with stagnant water. It’s also important to create effective drainage around your barn, repair any plumbing leaks and ensure stalls are dry. Additionally, moist, decaying leftover feed is an ideal breeding site for stable flies and houseflies. Ensure your feed room is dry and place waterers in well-drained areas and away from places where horses are fed. Properly dispose of all garbage and keep grain, supplements, and other feeds sealed under air-tight lids. 

Cleanliness in stalls and pastures also helps keep flies at bay. Manure is the housefly’s meal of choice and the more manure around your barn, the more flies you’ll attract. Remove manure from stalls every day and from paddocks at least once a week. If possible, move it to an off-site location or cover with a heavy tarp and treat on-site for later removal. Also, replace your horse’s stall bedding once a week and opt for shavings and sawdust. Straw tends to attract more flies. 

Several other barn hacks can help deal with flies. Prevent flies from entering the barn by positioning fans for downward and outward airflow. For stalled horses, large fans can deliver blasts of air to knock flies off their targets; for horses kept on pasture, make sure to provide access to open, breezy spaces. Adding screens around your feed and tack rooms, as well as stalls, can greatly cut down on flies, and residual insecticides specifically made for wall, ceiling and rafter application (versus products designed for use on horses) can deter bugs from the barn. You can also set up traps around the barn that use fly bait to lure flies onto a sticky surface or into a receptacle where they’re trapped and die.  

You can also combat flies outside the barn with fly parasites. These tiny, low-flying wasps use the fly pupa as a host to kill developing flies before they hatch thus preventing new generations from maturing. Simply release eggs near manure piles, water sources and other fly-breeding sites, and they’ll emerge as active wasps in about five days. (They don’t bite or sting people, horses or pets.) And, if at all possible, don’t pasture horses near cattle or other livestock. Cow manure, in particular, attracts more vicious horn and face flies.  

Fly-Control Arsenal

In addition to savvy barn management, beef up your fly-defense artillery to keep these health adversaries as far from your barn’s front lines as possible. Protective barriers like fly sheets, masks and boots provide external protection from insects and are made out of lightweight mesh fabrics for ventilation to help keep your horse cool throughout the warm fly season. Sheets protect horses from withers to rump and many also offer neck, chest and belly protection, which is especially beneficial for horses prone to sweet itch from biting gnats (See “The Main Offenders,” below). Fly masks protect crucial facial areas and some have ear and muzzle covers, and fly boots—also typically made out of a lightweight mesh—protect sensitive skin on the lower legs and can be helpful combatting stable flies that love to chew on horses’ legs. 

Topicals are another essential ammunition to combat flies. In addition to fly spray, these are also available in roll-on and wipe form and contain natural and synthetic insecticides to knock down or deter flies on contact. There are also insecticide-free products that use citronella, essential oils and other plant-based ingredients to deter bugs. Newer sprays combine tried-and-true ingredients like pyrethrin and permethrin with fatty acids to overwhelm flies’ sense of direction, so they’re less likely to land on your horse. 

Feed-throughs can provide another line of defense. They contain ingredients that pass through a horse’s system into manure to prevent larvae and pupa from developing and hatching. Typically given with a horse’s grain ration from early spring to late fall, these work best when used in conjunction with fly traps and topicals. Keep in mind, however, that feed-throughs won’t be effective if they’re not administered in the correct dosage to all horses at your facility. 

Formulated with ingredients like garlic and apple cider vinegar, supplements help deter bugs by making your horse less appealing as fly food. Some also contain diatomaceous earth, which passes through the horse’s system into manure where it creates an inhospitable environment for fly larva. 

The Main Offenders

Several hundred species of flies plague horses, but the following six are the most prevalent:

• Bot fly: Bot flies lay sticky eggs on a horse’s coat, muzzle, jaw, lips, throat and insides of legs. Larvae hatch in horse’s mouth and migrate to the stomach and intestines. They can cause a number of health issues and even death, so, call your veterinarian if you suspect bot flies.
• Face fly: Females feed on secretions around a horse’s eyes and nostrils and on blood from insect bites and wounds. They have sandpaper-like tongues that abrade eye-area tissue to stimulate tears, which can cause infection and even blindness.
• Gnat: Also known as “no-see-ums” or “midges,” gnats are most bothersome at dusk and dawn. They produce painful bites that can cause sweet itch (persistent skin breakouts that result in intense itchiness) in some horses. The resulting sores can be painful and cause horses to rub.
• Horn fly: These flies pierce a horse’s skin to suck blood like the stable fly. They prefer cattle but also attack nearby horses and can fly up to 10 miles.
• Housefly: Houseflies have sponge-like mouths and primarily feed on manure, garbage or bodily secretions. They don’t bite, but like to suck up secretions around wounds, eyes and nostrils.
• Stable fly: These flies bite by piercing the flesh to feed on your horse’s blood. They’re attracted to horses’ legs, resulting in stomping and tail flicking.

Beat the Heat & Keep Your Horse Hydrated

August of 2024 was the hottest month ever recorded, according to both NASA and the National Oceanic and Atmospheric Administration—and higher than average temperatures are predicted for much of the U.S. this year. When the weather heats up, it’s crucial to ensure your horse doesn’t get over-heated or dehydrated.

How Horses Cool Themselves

Besides humans, horses are one of the few mammals who cool themselves through perspiration in hot weather and during exercise or times of stress. Duncan Peters, DVM, MS, former head of the Hagyard Sport Horse program at Hagyard Equine Medical Institute in Lexington, Kentucky, explains that when your horse’s core temperature rises above its normal range (99 to 100 degrees F), his brain sends signals to the sweat glands to start pumping out sweat. As the sweat evaporates, it carries heat way from his skin, reducing his body temperature. During intense exercise, your horse can lose 3 to 4 gallons of fluid per hour via sweat and water vapor as he exhales.

Fluid loss can also depend on climate conditions; on hot, dry days, sweat can evaporate almost as quickly as it forms. “So be aware that even if you don’t see sweat pouring off your horse, he could have lost a large amount of fluid in dry conditions,” Peters said. “Horses can also be slow to replace that fluid, because the nature of their sweat delays their thirst response.”

When humans sweat, we lose mostly water, he explains. That water loss leaves us with an electrolyte imbalance that triggers thirst. Horses’ sweat, however, contains a higher concentration of electrolytes (key minerals like sodium, chloride, potassium, calcium and magnesium). Therefore, it takes longer for them to develop an electrolyte imbalance and feel thirsty.

Unfortunately in extremely hot and humid climates, sweating and the cooling effects of your horse’s breathing may not be enough to offset his temperature. This may not be too detrimental if the heat stress is brief; for example, if you exercise him for short period of time and he has ample time to cool off afterward. But Peters says if the stress is prolonged during intense exercise like cross country or hauling long distances in hot weather, the heat can began to build up in a horse’s body. Humidity can further exacerbate heat stress because when the air is saturated with moisture, sweat can’t evaporate fast enough to dissipate your horse’s body heat. He’ll keep sweating, but it won’t help cool him down.

Prevent Overheating

• Limit exercise in hot and humid weather.
• Pay attention to the Heat Index. This measure combines air temperature and relative humidity to estimate how hot it actually feels. (You can the find the National Weather Service heat-index calculator here.)
• Exercise your horse during the coolest time of the day—early mornings or evenings, depending on where you live.
• Always give your horse a thorough cooldown with lots of walking, cold baths and fans.
• During turnout, ensure he has access to shade or turn him out at night. If you horse is sensitive to bugs and needs a fly sheet, be sure to choose one made out of lightweight mesh with ample ventilation.
• During the hottest parts of the day, keep him stalled with ample air flow and fans.
• Encourage your horse to hydrate. Peters notes that even a 3% hydration loss is enough to affect your horse’s performance. Always off clean, cool free-choice water. At shows, offer him water at least every hour.
• Be mindful of your horse’s general behavior. Pay attention to his attitude, body posture, appetite, willingness to move freely (when turned out) and the relaxation of his muscles to determine if might be experiencing heat-related stress.
• As horses gain fitness, they become better at regulating their body temperature during exercise. As their bodies adjust to use energy more efficiently, Peters says, they produce less heat, sweat more readily and their sweat becomes less concentrated so they lose fewer electrolytes.

Danger Signs

For any horse, a buildup of body heat leads to fatigue and can have serious health consequences. The combination of prolonged hard work and hot, humid weather can be particularly deadly.

If your horse isn’t able to regulate his body temperature, he’ll overheat and may even suffer heat stroke. (In heat stroke, your horse’s sweating mechanism fails, and his temperature rises quickly to 106 to 110° F.) If he sweats excessively he will be at risk for dehydration, which disrupts key functions like circulation and digestion and can damage organs. In extreme cases, dehydration can be fatal.

Here are five signs that your horse might be in danger of over-heating:

• He’s breathing hard—and continues to. Peters says rapid, shallow breathing is common after exercises in hot weather, but it should slow fairly quickly to a normal resting rate, which is 20 breathes or below for most horses. If your horse’s breathing rate remains high, he might even pant to cool down.
• Prolong high temperature. A horse’s temperature can reach 106° F during intense work, but you should be concerned if it doesn’t drop a degree or two within 20 to 30 minutes.
• He seems exhausted or depressed. He might go off his feed. When dehydrated, horses generally don’t eat, but they usually will go for water. Horses, however, who are severely dehydrated may refuse to drink.
• His skin lacks resiliency. Test by pinching a fold of skin in three places–at midneck, high on his shoulder and low on his shoulder. If he’s well hydrated, the skin will snap back promptly; if fluids are low, it will stay folded up for a few seconds and then slowly flatten.
• His gums are dry and pale or white. (They should be moist and pink.)
• His eyes and/or flanks appear sunken.
• His gut is quiet. You should hear bubbles and gurgles; little or no noise indicates trouble. Your horse’s intestines typically contain a large amount of water that his body draws on as a reserve. When he gets dehydrated, gut motility slows, which can lead to digestive concerns.

If your horse is showing any of the above signs or you suspect he’s overheated:

• Hose your horse down with cold water. The water helps bring their core temperatures down to normal and provides overall relief from the heat. After bathing your horse, be sure to use a sweat scraper to thoroughly remove excess water and allow him to completely dry either under shade or in the barn with a fan before turning him back out in the sun. Otherwise, even a thin layer of water on his coat, especially in humid climates, can act as an insulator and trap body heat.
• Keep air moving as much as possible with fans and misters. When temps really soar and there is little to no access to breeze or shade outside, keep your horse stalled during the day with at least one fan for air circulation. Moving air carries heat away from your horse’s skin. If feasible, you might also consider installing misters or a misting fan for heat relief. Misters add water vapor to the air to lower its temperature.

• Always provide access to clean, cool water. Hydration is essential to prevent overheating, so encourage your horse to drink as much as possible. Peters says you won’t hurt him by giving him some water after exercise. It’s practically always safe to let your horse drink a small amount–up to a gallon–walk him for a few minutes and offer water again, he notes. If you let him drink intermittently, a gallon at a time, you may stay ahead of dehydration.
• Replenish lost electrolytes. Electrolytes are available in pellets, powder and paste form and can help replenish any vitamins or minerals lost through sweat, which can help protect him from dehydration and regulate muscle function and other body processes. Electrolyte supplementation can also encourage your horse to drink more water, which will help rebalance his fluids and ensure proper digestion.
• Offer salt: Adult horses need at least one ounce of salt per day. Since hay, grass and grain provide very little salt, horses are often lacking in this key mineral. Salt is essential for healthy nerve and muscle function. It also helps keeps fluids balanced and encourages hydration, especially in hot climates. You can add table salt to your horse’s grain (although, some horses aren’t keen on the taste of plain salt) or at the very least provide a salt block. Most horses, however, don’t get adequate amounts of salt from blocks or licks. If your horse isn’t keen on the taste, there are flavored salt supplements that many horses find palatable. 

When to call your veterinarian?

It depends on the severity of the signs and your horse’s general attitude. Peters says if his vital signs are improving and he’s alert, drinking water and interested grass or hay, you can probably handle the situation. If he seems dull or disoriented, turns down food or water or hasn’t cooled down despite your efforts, it’s smart to call your veterinarian. He can assess your horse’s condition, administer fluids by stomach tube or intravenously, and provide other supportive treatment as necessary.

For more summer turnout tips and advice on finding the right fly sheet, mask and boots for your horse, click here.