Exercise Key to Sidestepping Insulin Dysregulation in Horses

Veterinarians often assign blame to unsuitable diets and long-term obesity as primary causes for insulin dysregulation (ID). A new study shows, however, that lack of exercise is an important risk factor for ID, and that even light exercise appears to reduce the risk of this endocrine abnormality.^*

In the study, 29 Finnhorses underwent testing for ID every other month for one year using the oral sugar test. Once recruited, each horse’s diet and exercise level were kept as consistent as possible for the duration of the study.

Researchers documented season and physical activity level during the study as well as various physical measurements, including weight, cresty neck score, body condition score, heart-girth circumference, neck circumference, and circumference of the widest part of the abdomen.

While each of these measures was considered potential risk factors for ID, only exercise level was found to be a statistically significant risk factor for ID. Seven of the horses were not exercised at all during the one-year study. The remaining 22 horses were involved in mild to moderate work, typically riding and driving, for an average of 72 minutes a day.

Horses that did not exercise were over 7.5 times more likely to have ID than horses that had some physical activity.

“The study also found that ID status in the tested horses varied throughout the year. No peak month was identified, suggesting that other management factors, such as diet or exercise, may have influenced ID status more than season,” said Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research.

These results also suggest that horses with physical traits indicative of EMS (obesity, cresty neck) whose ID test results fluctuate and appear “borderline” may benefit from repeat testing. In the study, these horses were referred to as “suspicious” animals.

“These horses could be pushed over the edge into full-blown ID and EMS with small changes in management, such as a decrease in exercise due to weather or injury, or a decrease in the owner’s time to ride,” Crandell explained.

The horses in this study exercised just over an hour per day, which suggests that regularity of exercise may be more important than a certain intensity level. In humans, regular physical activity reduces the risk of insulin resistance even without weight loss. Further studies evaluating the amount and intensity of exercise that benefits horses with or at risk of ID are warranted.

“Horses with ID are often easy keepers, so they do not require concentrated calorie sources. They should be supplemented with nutrients not found in all-forage diets,” Crandell recommends. “For these horses, a well-formulated vitamin and mineral supplement is a wise choice. Feed as the manufacturer recommends.”

^*Karikoski, N.P., J.R. Box, A.K. Mykkänen, V.V. Kotiranta, and M.R. Raekallio. 2021. Variation in insulin response to oral sugar test in a cohort of horses throughout the year and evaluation of risk factors for insulin dysregulation. Equine Veterinary Journal:13529.