Question

I have a laminitic, insulin-resistant mare, a 13.2-hand Welsh Pony (Section B). Her insulin levels remain elevated even though she is given metformin twice a day at a rate recommended by the veterinarian. I am happy with her weight, even though ribs are visible, but she has fat deposits. Her diet includes two scoops of senior feed, 7.3 kg (16 lb) of soaked hay, and free-choice salt. Can you give me any suggestions?

Answer

The primary goal for managing a horse with insulin resistance (IR)/equine metabolic syndrome (EMS) is to control weight, improve insulin sensitivity, and lower the risk of laminitis through correct nutritional management.
The diet you are currently feeding is high in fiber and low in starch/sugar, which is good for your mare in preventing laminitis. The diet, however, is missing some important nutrients for general health and well-being, including essential trace minerals. My recommendation is to balance the forage diet with a high-quality balancer pellet. Fed at 400-600 g per day, this will provide all the additional nutrients your pony needs without contributing calories or starch/sugar, which you need to avoid with an IR/laminitic horse.

You commented that you are feeding a lot of metformin, which is a common medication for IR horses. Metformin is used in humans to improve the action of insulin. Research in horses has shown that intestinal absorption of metformin in horses is very low and certain studies on metformin supplementation did not improve insulin resistance in IR ponies. Because of this new research, many people are not using it on IR ponies.

You did not mention your pony’s age or if she is lame, but exercise is important to help improve insulin sensitivity. Turnout in a field (with a muzzle) is helpful in addition to ridden exercise.

Research has also recently shown that supplementation with DHA and EPA omega-3 fatty acids (from fish oil) may also improve insulin sensitivity in horses, so if you can locate a good source of fish oil in the U.K., we would recommend 30 ml per day.