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Can Exercise Protect Foals From Injuries Later In Life? Tune In To Find Out

Does exercise help young horses avoid injury? That's the topic of this month's episode of Morris Animal Foundation's “Fresh Scoop” podcast, available now for streaming and download. Host Dr. Kelly Diehl, the Foundation's Senior Director of Science and Communications, interviews Dr. Annette McCoy, Assistant Professor of Equine Surgery at the University of Illinois at Urbana-Champaign College of Veterinary Medicine.

McCoy discusses leg fractures in horses and her new Foundation-funded study, which is evaluating the long-term effects of a moderately strenuous exercise plan on bone development in foals. Her team is collecting data for an algorithm they hope to use to design exercise programs for foals to reduce risk of injuries later in life.

Dr. McCoy is a Diplomate of the American College of Veterinary Surgeons.

“Fresh Scoop” is Morris Animal Foundation's monthly veterinary science podcast designed to appeal to practicing veterinarians, veterinary technicians or students, as well as animal-loving science geeks. Episodes are available on iTunes, Spotify, and Stitcher, as well as the Foundation's podcast page.

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.

New Study Will Help Determine Exercise Effects On Bone Health

Researchers at University of Illinois at Urbana-Champaign (UIUC) are investigating whether mile-long trot sets might protect foals from leg fractures later in life. Leg fractures can happen in any horse, but lower leg fractures are of more concern in horses that race or jump competitively. Most fractures occur in horses that are between two and 10 years old.

Dr. Annette McCoy, Assistant Professor of Equine Surgery at the UIUC College of Veterinary Medicine and member of the research team, notes that mild exercise early in life stimulates bone growth in horses – particularly in areas prone to fracture — though how is not completely understood. McCoy will see if parallels can be drawn from human medical studies, which have shown that kids who exercise are less prone to injury as adolescents and adults. The bone changes the human subjects experience from exercise seem to be sustained over time.

McCoy and her team will study 12 Standardbred foals housed on the university farm beginning when they are eight weeks old. The scientists will perform a baseline CT exam to measure bone density and volume on the forelegs of each foal. The foals will then be split into two groups: one group will complete an eight-week exercise plan where they trot rapidly over 1,500 yards once a day, five days per week; the second group will serve as the control and will not be exercised. In a previous study, McCoy found that foals living outside were relatively inactive nearly 85 percent of the time.

At 16 weeks old, the foal's forelegs will be scanned again to compare bone development. At 12 months old, a final CT scan will be performed. A computer model will predict the effects of exercise interventions on bone properties.

Diet And Exercise Key To Managing Tying Up From PSSM

Polysaccharide storage myopathy (PSSM) is a glycogen storage disorder in horses that causes muscles to cramp. It occurs primarily in horses with Quarter Horse bloodlines, like Paints and Appaloosas, but it can also occur in draft horses, draft crosses and Warmbloods.

In normal horses, insulin goes from the blood and is stored as glycogen in the muscle and liver cells. In horses affected by PSSM, a large amount of sugar (glycogen) is stored in the muscle and up to four times the typical amount of polysaccharide (an abnormal form of sugar) accumulates in the muscles.

Horses with PSSM are generally in good weight and have a quiet temperament. They often experience a PSSM episode when they begin training or go back into training after a layup, when their movement is restricted. The episode normally comes on after the horse has been walking and trotting for about 20 minutes.

When a horse has a PSSM episode, their muscles get very stiff and hard, especially over their hindquarters; they will sweat profusely, refuse to move, and their flanks may tremble. When they stop moving, the horse may stretch out as if urinating. Foals with PSSM often show signs of muscle pain and weakness when they have diarrhea or an infection like pneumonia.

Horses that have PSSM should not be fed sweet feed, wheat, oats, barley, molasses or feeds high in starch. They should also be exercised daily. Exercise encourages the body to use glucose properly and improves energy metabolism in skeletal muscle.

Researchers have found that if horses have only their diet adjusted, about 50 percent will improve. If both diet and exercise are adjusted, more than 75 percent of horses with PSSM will have few or no tying-up episodes. Though it may seem counter-intuitive, horses should be turned out and encouraged to move as soon as a PSSM episode has dissipated.