Insulin Resistance And The Pregnant Mare

When a mare is pregnant, all her body systems are geared toward providing nutrition for the growing foal. One way nature accomplishes this is to induce a degree of insulin resistance in the mare. This helps divert glucose away from the mare’s own tissues to ensure a generous and steady supply for the fetus.

For most mares, this isn’t a problem, but if the mare was insulin-resistant already, it can put her at a higher risk for developing laminitis. Most people think the pregnant mare has to have a highly supplemented feed to be certain all the needs of the mare and foal are met during this critical time. However, concentrated fat or carbohydrate sources all but guarantee laminitis in these mares.

The filly in this photo is only 6 days old, but she’s beautifully muscled, an excellent weight for a foal this young and has straight legs with good bone. Her dam didn’t see a speck of grain for the last half of her pregnancy.

Because the mare is a Morgan, her caretaker did not want to risk laminitis in this pregnancy. Starting with a hay analysis, a diet was constructed for the last part of her pregnancy. It was determined that 18 lbs. of hay and 2 lbs. per day of a mixture of 2 parts beet pulp and 1 part wheat bran would meet the calorie and protein needs of the last month of pregnancy. Since the mare was a bit underweight, she was started on that amount and gained weight nicely despite being pregnant.

The next thing to consider was her mineral requirements. Using average analysis figures for wheat bran and beet pulp (you can find these at, 800-496-3344), and the mineral profile from the hay analysis, mineral deficiencies and imbalances from the base diet were calculated and a custom supplement to correct these was mixed in a base of ground stabilized flax to provide essential fatty acids. All that was left to add was vitamin E and salt. As you can see, all turned out well.

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