Breaking the cycle of insulin resistance / equine metabolic syndrome / hyperinsulinemia

If you suspect or have confirmed your horse is insulin resistant, here are a few things that may help break the cycle of chronic laminitis, irritability, and obesity that accompany this disease, which affects an estimated 1 in 10 horses in the United States.

What is Insulin Resistance/Equine Metabolic Syndrome?
Insulin allows glucose (food) to enter cells. Insulin-resistance is when cells do not allow glucose to enter and be processed, thereby creating an excess of insulin in the bloodstream. The liver then converts the excess glucose into fat, creating the cresty neck and fat pads commonly seen on metabolic horses. Insulin resistance is considered by some to be a genetic advantage for survival. All horses experience some degree of this metabolic process in the fall, as the condition stimulates a horse to put on weight before the harsh winter months when less food would typically be available. When a horse is obese, fat gets stored in the skeletal muscles, which causes insulin to stop working. Insulin resistance is considered a dynamic state, so if a horse is diagnosed insulin-resistant it doesn't necessarily mean the horse will always be insulin-resistant.

Symptoms of IR:
  • Chronic tenderness in the hooves that never seems to go away, or comes and goes
  • Cresty neck, fat pads located at the tailhead or shoulders, a crease down the back, "easy keeper"
  • Bruised white line visible when the horse is trimmed or shod (hemorrhaging of the laminae)
  • Insatiable appetite
  • General irritability
Causes of IR:
  • Obesity
  • Genetic predisposition ("easy keeper")
  • Stress
  • Retained placentas, drugs such as dexamethasone and corticosteroids, and over-exertion (myositis - inflammation of the skeletal muscles)
Treatment Options:
  • Above all else, EXERCISE is considered the most effective treatment option. As little as 10 minutes of exercise a day can keep insulin resistance in check.
  • Reduce the sugar AND carb content in the horse's diet. This includes feed, hay, and grass. Keep in mind that just because a feed claims it is low starch does not mean it is also low sugar. Do your research.
  • Horses prone to IR increase insulin production when they eat sweet grass. The sugar content in grass tends to be lowest when the grass is not stressed by drought and is in the shade. Ever notice how horses tend to prefer grass in sunny areas? It's sweeter! Have your hay tested if possible and remember (to quote Katy Watts) that "sugar is not green". Stemmy, brown grass hay can be much higher in sugar than soft, leafy, green hay. Hay harvested in the morning and cured on cloudy days tends to be lower in sugar - talk to your hay farmer. Short grass is stressed, and is usually much higher in sugar than grass that is long (but without seed heads). Long, "lush" grass shades itself to some degree and can allow the horse to eat more forage with less insulin response.
  • Turn horses out on pasture during the hours of 3am-10am. Sugar is highest during the late afternoon.
  • Use a grazing muzzle, which can decrease grass intake by 75%.
  • If your horse must be dry-lotted, it should be free of weeds and grass. Weeds can be much higher in sugar than grass. The dry lot area should be as large as possible and allow the horse to canter if he wants. Please put a buddy in with him to support him emotionally and physically (movement).
  • Magnesium and chromium supplements have been anecdotally successful, but not proven.
The majority of the information presented here was from my notes at the Carolina Laminitis Symposium on May 15, 2010. Please support the Animal Health Foundation and Katy Watts in their research.