Managing Insulin Resistant Horses


Grazing Horse
While pasture grazing may not be an option for overweight, insulin resistant horses during certain times of the day or seasons of the year, access to free-choice forage is still essential.

Do you have an overweight horse? Chances are he is insulin resistant. Excess body fat leads to elevated insulin, and blood glucose levels are slow to return to normal. Elevated insulin leads to more body fat storage, which leads to greater insulin resistance, and the vicious cycle continues. Even horses of normal weight can be insulin resistant, exhibited by regional fat deposits along the neck, shoulders, tailhead, and back. These horses are labeled as having Metabolic Syndrome, another term for insulin resistance.

The opposite of insulin resistance is insulin sensitivity. That simply means that the horse’s cells respond better to insulin and there is no longer a need for the pancreas to continually pump out high levels of this hormone. Storage of body fat normalizes, as well as blood sugar levels. In attempting to reach this goal, many horse owners will restrict feed – put their horse on a diet. The problem is that horses are designed to graze. They need to consistently chew to neutralize stomach acid (through saliva production, a natural antacid). Left with an empty stomach, your horse can suffer a variety of health issues, experience a hormonal stress response that increases the blood insulin level, and ironically, remain overweight. This is because excess insulin tells the body to hold on to body fat and refrain from burning it for energy.

Free-Choice Forage

Consistently eating forage, on the other hand, matches what a horse would naturally do. It allows cortisol (stress hormone) levels to decline, making the cells more responsive, more sensitive, to insulin. How eating affects insulin sensitivity was recently evaluated by researchers at Louisiana State University. They determined that hay-deprived mares experienced a greater degree of insulin resistance and less insulin sensitivity than those mares who were fed hay ad libitum (free-choice). These results are consistent with a horse’s natural eating pattern. A healthy, insulin sensitive horse is a horse that will not easily gain weight when fed forage free-choice. A healthy horse will burn body fat and not store excessive amounts.

Calorie reduction, though important, should be accomplished by reducing or even eliminating commercial feeds and cereal grains. But never reduce forage intake. While pasture grazing may not be an option for your overweight, insulin resistant horse during certain times of the day or seasons of the year, you should always offer hay, day and night, 24 hours a day. Be sure to provide a vitamin/mineral supplement to fill in the gaps that exist with hay. To do this effectively, it is best to make sure that your hay is low enough in non-structural carbohydrates (NSC) and calories. Therefore, testing is recommended.** Once you know your hay has a percent NSC level of at most 12%, and no more than .89 Mcals/lb (1.96 Mcals/kg), feed it free-choice. (%NSC = %Starch + %Water Soluble Carbohydrates.)

When forage is restricted, your horse perceives this as “survival mode.” He needs to hold on to body fat because it is uncertain when food will again be made available. But once he gets the message that hay is always there, that he doesn’t run out, not even for 10 minutes, then and only then will your horse understand that he can walk away and the hay will still be there when he returns. He starts to calm down his eating, eating more slowly, and eating less – eating only what his body needs. Insulin sensitivity increases, and body weight begins to normalize. With the help of exercise, your horse’s cells will respond to insulin better and no longer store excess body fat. It’s amazing to see – it does happen.

Give your horse a chance to be a horse and to tell you how much forage he needs.

Liked this article? Here are others on equinenutrition
Selecting the Right Hay for Your Horse
Feeding Fruit to an Insulin Resistant Horse

Dr. Juliet Getty is an internationally respected equine nutritionist available for private consultations and speaking engagements. At, sign up for her informative—and free—monthly newsletter, Forage for Thought, read articles, join her nutrition forum, enroll in upcoming teleseminars and purchase previously recorded events.


  1. I don’t believe it. If my mini horse had free choice he’d eat non stop 24 hours a day and would be a balloon. There really are easy keepers out there who cannot have free choice. It depends on the horse. Instead of free choice I feed my horse 4 times a day so that he always has some food in his ravenous stomach.

  2. Thank You for the information. I have one cresty neck mare and is heavier, and trying to think what to do to help her.


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