temperature | Horse Racing Free Tips

Chill Out: Researchers Compare Cooling Methods For Equine Athletes

Elite athletes like racehorses and three-day event horses sometimes exercise on hot, humid days, often resulting in high body temperatures that must be lowered quickly before heat-related stressors set in. While much research has been performed on effective cooling strategies, a new study compared several different cooling methods.^*

[Story Continues Below]

Thoroughbreds were exercised on an inclined treadmill until the pulmonary artery temperature reached 107.6 degrees Fahrenheit. One of five cooling methods was then implemented. The methods included:

Walking on a treadmill with one commercial fan placed 6.5 feet in front of the horse set at low velocity to simulate the breeze that would occur if walked outside (control);
Walking on a treadmill with two fans placed 13 feet in front of the horse set at almost twice the airflow of the fans used in the control;
Cooling with intermittent application of cold water (4.2 gallons at 50 degrees Fahrenheit) every three minutes on its body behind the neck, scraping as much water as possible after dousing; two cycles of dousing performed with return to treadmill walking and two low-speed fans in the interim;
Cooling with intermittent application of cold water (16 liters; 50° F or 10° C) every three minutes on its body behind the neck with no scraping; two cycles performed with return to the treadmill and two low-speed fans in the interim; and
Showering continuously with tap water (78.8 degrees Fahrenheit) for 30 minutes with no return to the treadmill.

To determine the most effective cooling method, researchers measured the time necessary for the pulmonary artery temperature to return to 102.2 degrees Fahrenheit or lower, and recorded the rectal temperature at 30 minutes after onset of cooling.

The researchers concluded that showering the horse continuously with a large volume of tap water resulted in the most rapid decrease of both pulmonary artery and rectal temperatures, signifying its effectiveness as a way to achieve cooling in hot, humid conditions.

Sweat production goes hand-in-hand with exercise. Multiple factors determine how much sweat is lost doing any exercise bout (heat, humidity, and work intensity, for example). Light exercise with minimal sweating may induce a sweat loss of 1 quart to 1 gallon, while high-performance horses at the peak of exertion may have losses of 12.25 to 3 gallons.

Because large quantities of electrolytes are lost in sweat, electrolyte supplementation becomes a key factor in managing the diets of performance horses. Choose research-proven electrolytes formulated by specialists in equine nutrition and exercise physiology.

Electrolyte supplementation is not season-specific. Well-formulated electrolytes should be used whenever horses sweat on a daily or near daily basis, no matter the season.

^*Takahashi, Y., H. Ohmura, K. Mukai, T. Shiose, and T. Takahashi. 2020. A comparison of five cooling methods in hot and humid environments in Thoroughbred horses. Journal of Equine Veterinary Science 91:103130.

Genetic Marker Tied To Anhidrosis Discovered; Similar To Cystic Fibrosis

Sweating is a critical tool to keep horses comfortable and healthy, but chronic idiopathic anhidrosis, a dangerous equine condition can impede their natural cooling mechanism and cause performance and health issues. For the first time, University of Florida's Institute of Food and Agricultural Sciences (UF/IFAS) researchers have identified genomic markers that cause the potentially fatal condition.

The genomic mapping study gave researchers a discovery-based approach to attacking this disease, pushing aside prior assumptions about the disease's causes. A team of UF scientists from the Genetics Institute and the College of Veterinary Medicine used genetic markers like signposts, looking for the common genomic markers found in horses that had chronic idiopathic anhidrosis disease. These genetic signposts pointed to a defective potassium transporter that likely hinders sweat function.

[Story Continues Below]

“Now that we know which biological pathways cause the condition, we hope to design specific strategies to intervene,” said Samantha Brooks, UF/IFAS associate professor of equine physiology. “We found that this disease has similarities to cystic fibrosis which has many drug treatments available and in development. Knowing this, we can start to consider ways to treat these horses that suffer from this condition, helping them sweat more normally over longer periods of time.”

Genetic mutations leading to cystic fibrosis also impact ion channels and gave researchers some clues as to how this particu.lar defective potassium transporter might work. Additional research is needed to fully understand, but researchers found a change in the protein that alters when this ion transporter turns on and off. The stress of the sweat gland attempting to function with this faulty transporter likely destroys the ability to sweat over time.

“Using histology, the study of the structure of the tissues, previous work found that the sweat glands become damaged after horses live with chronic idiopathic anhidrosis over long periods of time,” Brooks said. “That is why we have not been successful in reversing the disease and restoring sweat function. Trying to sweat without a functional ion transporter could be the cause of the damage to the cells in the sweat gland. We may not be able to reverse that.”

Having chronic idiopathic anhidrosis is like driving a car on a flat tire, Brooks explained. Over time, a horse living with this disease experiences impacts to their overall health beyond the inability to sweat. Living with the condition becomes a quality-of-life concern and unlike other kinds of anhidrosis, chronic idiopathic anhidrosis cannot be solved quickly or cured.

“The saddest part about this disease is that we do not have any specific way to treat the condition right now,” Brooks said. “We can see what is happening and try to address the symptoms but because we do not know exactly what is causing it, we cannot attack the disease. So far, no supplements or medications have been tested and proven to work in a scientific study.”

Most chronic idiopathic anhidrosis horses sweat normally when they are young, but their cells accumulate damage over time, especially in extreme environments like Florida. Older horses experience more severe clinical signs such as critical hyperthermia as they lose more sweat gland function over time.

“We also do not understand the severity aspect,” said Laura Patterson Rosa, animal science graduate student and lead author of the study published in the Journal of Investigative Dermatology. “We don't understand why some horses have it worse than others. Even if it is chronic, the severity differs.”

In their study, scientists were surprised to find the genetic marker that causes chronic idiopathic anhidrosis is a common marker, particularly in sport-type horses like Quarter Horses and Thoroughbreds.

“I think there are a lot of horses out there struggling to live with the early stages of this disease, but owners and caretakers are just not aware of it,” Brooks said. “Long periods of hot humid weather here in the southeastern U.S aggravate the condition, increasing the chances an owner will notice the problem, but it can be just as much of an issue for horses in more northern locations. You may not think of places up north as having a hot summer that would make it hard for these horses to live, but if a horse has chronic idiopathic anhidrosis it might just take a single day in the 90s to trigger an episode of overheating. That can be very startling to their caretakers, and miserable for the horses. Especially if they live in a climate where those hot days are rare.”

The first signs of an insufficient sweat response and poor cooling are often a decrease in performance of the horse. They may get more tired during exercise, and although they still have some ability to sweat, it is often difficult for caretakers to accurately assess the volume of sweat they are producing. Over time as their ability to sweat decreases, their coats become dry and during overheating episodes it becomes more noticeable. Another side effect includes skin flakiness, rashes and an overall poor hair coat since the sweat glands are no longer distributing healthy oils to the skin.

“If your horse is one of the 2 percent affected by this disease, this diagnosis can be an absolute disaster,” Brooks said. “Still, I think a lot of these horses are probably out there doing the best they can. They may have slightly decreased performance at first or become a bit lazy in the summer. They are often confused for horses that have allergies, asthma or a respiratory infection because they pant to cool themselves. At first glance, they look as if they are struggling to breath, but really, they are struggling to cool themselves.”

Horse owners who suspect their horse has chronic idiopathic anhidrosis should regularly take the animal's temperature and consult their veterinarian. It may appear that the horse has a fever, but in reality, their basal body temperature is elevated during hot times of day because they cannot regulate it on their own through sweating. Taking their temperature regularly can be a critical component for managing this disease and can help horse owners monitor how well efforts to help keep their horse cool are working and is an important weapon to attack this disease.

“This is a very dangerous disease,” Brooks said. “We often see sweating as a nuisance, but we forget that hyperthermia can be a very life-threatening emergency. This is the time of year, when temperatures start to rise, it is important to revisit this idea and increase awareness among horse owners and caretakers about the condition.”

Horses that have not previously struggled to stay cool and perform may still have issues in the future. As the disease progresses each year and the climate continues to warm, chronic idiopathic anhidrosis is a condition that could be diagnosed more often and become worse for those horses already affected with the disease.

Looking ahead, the research team would like to launch a new project, using samples from horses with and without the disease to measure how much of this disease is due to changes in the function of this particular potassium transfer problem compared to other factors, like the environment. Developing therapies to treat or cure chronic idiopathic anhidrosis and tests to detect a propensity for the condition are future goals as well.

“In our first study we went out and found horses with chronic idiopathic anhidrosis so we would love to measure how much of this disease is due to the potassium transporter and how many horses carry this variant,” Brooks said. “The next step, in collaboration with our colleagues at the UF college of veterinary medicine and pharmacy, will be to see if we can find a compound developed for humans that alters potassium transfer, potentially offsetting the genetic factors contributing to chronic idiopathic anhidrosis in the horse, and administrable in a way that is feasible and economical in such a large animal.”

“Through directed genomic selection, we can eliminate chronic idiopathic anhidrosis from the horse population,” Rosa said. “But that will take time and further research.”

Feeling Hot, Hot, Hot

While many horses wear leg boots or wraps when working to prevent injury, recent studies report that these boots may increase the temperature leg temperature and harm the superficial digital flexor tendon (SDFT), reports The Horse.

Researchers from Middle Tennessee State University (MTSU) created a study to determine whether different leg wraps increase the temperature of the leg during exercise. Graduate student Luke Brock explained that the equine lower limb has little muscle below the knee and hock, so it cools itself by taking the heat away from the skin's surface. Using a boot or bandage to the leg creates an insulating effect, which can harm the SDFT.

Heat dissipation depends on leg protection design and application, material permeability, heat produced during exercise, temperature and humidity outside, and rate of ambient air exchange. The MTSU research team compared six types of leg protection: a neoprene boot, perforated neoprene boots, plant-based neoprene boots, cross-country boots, elastic track bandages, and fleece polo wraps.

Each horse wore each type of boot over six exercise sessions, which involved 20 minutes of work followed by 180 minutes of standing recovery. Each horse wore one boot on a foreleg; the other leg served as a control. A special tool was used to measure limb temperature and humidity every minute the horse wore the boot.

The team discovered that the leg not wearing any boot had the lowest temperature. The fleece polo wrap caused the most heat and humidity buildup. All limbs wearing boots rose to temperatures that could harm tendon cells. None of the treated limbs returned to their baseline temperature after the recovery period.

The researchers determined the limb's cooling ability is impaired by boots and wraps, which can damage the SDFT. Before applying boots, the team recommends riders consider the intensity of the workload, the ambient temperature, boot design and material, and how the horse goes.

If a horse wears leg protection, it's best to remove it as soon as possible once the horse is done working, then cold horse the legs, they conclude.

Do We Need To Practice Social Distancing With Our Horses?

Social distancing, mask wearing, hand washing, and the dreaded nasal swab have become part of our normal life during the COVID-19 pandemic. The equine industry faces similar types of outbreaks, but placing a mask on a horse isn't feasible. However, there are ways to prevent disease spread within the equine community.

The recent increase in horses affected by herpesvirus neurologic disease in North America and Europe reminds us that herpesvirus (EHV-1) remains a constant threat for horses. The virus, which causes upper airway infection and abortion, is highly contagious and easily transmitted between horses. Although there are vaccines for this virus, these vaccines are not completely effective and do not protect against the neurologic form of the disease, which is often fatal. The best protection to limit the spread of this disease is appropriate biosecurity, including isolation and social distancing.

Like COVID-19, equine diseases such as equine herpesvirus and equine influenza are highly infectious and spread by contact or by inhalation of micro-organisms on particles in the air or water. When an infected horse coughs or sneezes, tiny particles are spread. Viral diseases can also be spread by horse-to-horse contact or by contamination on commonly touched surfaces. Bacterial diseases such as Strangles are also transmitted through contact—from horse to horse or by horses touching common areas such as watering systems, tack, and grooming equipment. Both viruses and bacteria can be spread by humans working with an affected horse and carrying it to other horses.

Keeping horses separated is one of the most important steps in biosecurity to help prevent disease spread. When an infectious disease is suspected or confirmed, all horses in the same facility or on the same premise are at risk of becoming infected. Keeping horses separated in stalls or at a separate facility is crucial to stop the transmission of diseases to other horses. With very contagious diseases like equine herpesvirus, a quarantine is often necessary to stop all horse movement and limit movement of people on the affected premises.

Social distancing only works if appropriate sanitation measures and careful separation of tools and equipment are in place while caring for infected horses. Just as hand washing is needed to help control Covid-19, it is important that hands, clothing and any objects that come in contact with more than one horse are sanitized between horses.

If a horse is suspected or confirmed to have an infectious disease, horse owners should employ the following protocol to help prevent disease spread.

Immediately isolate the horse showing signs of an infection.
Implement movement restrictions of the affected horse and possibly exposed horses until the situation is evaluated.
Contact your veterinarian or the event veterinarian and ask what you should do.
Inventory horses, identify and isolate potentially exposed horses, and immediately implement health monitoring: take temperature twice daily (a temperature above 101.5° F suggests the horse has an infectious disease) and observe for clinical signs of depression or abnormal behavior.
When more than one owner or caretaker is involved, establish communication with all parties.

Additional protocol detail is available here.