Predicting Laminitis Risk in Horses with Insulin Dysregulation

Hoof problems occur regularly in horses with the endocrine disorder known as insulin dysregulation. Prolonged periods of hyperinsulinaemia, or high levels of circulating insulin, a hallmark of the disorder, trigger laminitis in some predisposed horses.

Diagnosing insulin dysregulation can be tricky. The gold standard test for insulin dysregulation is a dynamic test called the intravenous glucose tolerance test. Although generally reliable, this test has drawbacks, as it is time-consuming and expensive, and it must be performed at a veterinary clinic. As an alternative, the oral glucose tolerance test can be performed in a field setting but results are variable.

Researchers recently explored another approach to the diagnosis of insulin dysregulation that involves the identification of biomarkers.^* Biomarkers are circulating molecules involved in normal cellular processes. In addition to helping diagnose disease, biomarkers may provide additional information as to why insulin dysregulation causes laminitis in only some horses.

In this study, researchers characterized the metabolome of ponies with varying degrees of insulin dysregulation before and after feeding a diet high in nonstructural carbohydrates (NSC). Specifically, plasma from 10 pre-laminitic and 10 non-laminitic ponies was used for metabolomic assay. Metabolomics is the scientific study of chemical processes involving metabolites, the molecular substrates, intermediates, and products of cell metabolism. The assay used in this study included nearly 200 metabolites related to oxidative processes, lipid degradation, and inflammatory signaling.

By the conclusion of the study, researchers pinpointed six glycerol-based phospholipids that could serve as potential biomarkers for future risk of laminitis. While the results of this study are promising, the researchers indicated that “the prognostic value of the identified biomarkers for laminitis remains to be investigated in further metabolomics trials in horses.”

“As research into biomarkers continues to grow, owners are encouraged to feed horses appropriately to minimize the development of insulin dysregulation,” said Kathleen Crandell, Ph.D., a nutritionist with Kentucky Equine Research. “Much of the dietary management depends on keeping horses in moderate body weight and choosing appropriate feedstuffs.”

In regard to nutritional strategies, focus on key components, including:

• Use of an appropriate forage, typically a grass hay of moderate quality that is free of weeds, dust, mold, and any other impurities. Because many horses with insulin dysregulation are easy keepers, it is best to avoid legume hay (alfalfa or clover) or top-quality grass hays that have been harvested at early maturity. These types of hays will generally have more calories than easy keepers require. Hay should be fed in a way that slows intake.
• Hay should be low in NSC—sugar and starch. In order to determine the NSC level in hay, it must be tested. If you are unable to test the hay, steam or soak hay meals in water for at least 30 minutes (hot water) or 60 minutes (cold water), and remove it from the water before feeding. Soaking removes a substantial amount of sugars, as does steaming.
• Grazing should be limited through the use of a drylot or grazing muzzle.
• If a horse can maintain its weight on forage alone, there is no need to feed a traditional concentrate, as that will only add unnecessary calories. Instead, choose a high-quality ration balancer pellet or a vitamin and mineral supplement.
• If a concentrate is necessary, avoid ones high in NSC. Low-starch feeds derive the majority of their calories from fermentable fiber and fat.
• If the horse is sound, consider an exercise schedule that consists of at least 30 minutes of exercise of sufficient intensity that raises heart rate five or six days a week.
• Consider supplementation with EO-3, a marine-derived oil that confers the omega-3 fatty acids that improve glucose intolerance and bolster anti-inflammatory mechanisms.

Once a horse has been diagnosed with insulin dysregulation, it is important to institute dietary changes immediately to avoid the possibility of laminitis.

^*Delarocque, J., D.B. Reiche, A.D. Meier, T. Warnken, K. Feige, and M.N. Sillence. 2021. Metabolic profile distinguishes laminitis-susceptible and -resistant ponies before and after feeding a high sugar diet. BMC Veterinary Research 17:56.