How important is making sure my insulin-resistant mare gets the right minerals in her diet?

Hoof Nutrition Intelligence is a twice-a-month web segment that is designed to add to the education of footcare professionals when it comes to effectively feeding the hoof. The goal of this web-exclusive feature is to zero in on specific areas of hoof nutrition and avoid broad-based articles that simply look at the overall equine feeding situation.

Below you will find Part 1 of the latest question and answer installment that you can share with your footcare clients.

Q: How important is making sure my insulin-resistant mare gets the right minerals in her diet?

By Eleanor M. Kellon, VMD

A: The best place to start supporting your insulin resistant (IR) horse is by feeding a low sugar and starch diet along with a balanced intake of key minerals. Minerals have direct and indirect involvement in virtually every action in the body, and have important effects on IR and its consequences.

While IR is different in the horse than in the human, the same basic principles apply, which is evidence of activated antioxidant defenses in the tissues of IR horses.

Building the horse’s own antioxidant basic defenses is most effective. This includes providing the superoxide dismutase (SOD), catalase and glutathione peroxidase enzyme systems, as well as the antioxidants glutathione, CoQ10, carotenoids, vitamin A, flavanoids, vitamin E and vitamin C.

SOD absolutely requires copper and zinc. Catalase requires iron, which is not an issue as the typical equine diet supplies plenty of iron.

Glutathione activity depends on selenium, a very common deficiency. Selenium is also essential for the generation of the active form of thyroid hormone, T3, from T4.

Zinc is a commonly deficient mineral and low serum zinc levels are associated with IR and type 2 diabetes in humans and rats. Supplementation of zinc supports defenses against type 2 diabetes in rats. Exactly why has not been determined, but zinc is involved in insulin release and sensitivity as well as being an antioxidant in SOD.

Like zinc, copper is critical for SOD function, as a copper deficiency causes IR and fatty livers in rats. Low liver copper is found in human fatty livers. Deficiency is also linked to higher liver iron in IR, a known problem in IR horses too.

Magnesium has been associated with IR for 40 years with hundreds of human-focused research papers dedicated to the subject. Magnesium is not a treatment, but by correcting a deficiency it makes the disease easier to control.

Magnesium dietary intake and magnesium status (whole body levels) are associated with strong defenses against IR and they deteriorate when someone develops IR. It becomes a cycle you need to stay on top of in order to allow stabilization.

A 2013 study included almost 2,000 non-diabetic human subjects that were followed for 15.6 years. Magnesium intake was a “significant protective factor” against type 2 diabetes, including progression from IR to diabetes. Researchers were able to predict who would most likely become IR by looking at their magnesium levels.

Magnesium increased the insulin receptor number and sensitivity in experiments done with IR rats. A magnesium deficiency interferes with insulin signaling and has also been linked to the activation of allergic and inflammatory reactions.

Iodine is essential for the production of thyroid hormone and low iodine status has been identified in human patients with type 2 diabetes. Normal thyroid function is required for insulin sensitivity.

IR horses in some cases may also have low thyroid hormone levels. This is often recognized as euthyroid sick syndrome, meaning it is an effect rather than a cause. With correct levels of selenium and iodine, and control of IR, the levels will rise again in most of these affected horses. Low thyroid is not a primary part of the syndrome, but can make some horses very depressed and lethargic. Thyroid supplementation can be used, but by addressing the above you will not need long-term supplementation.

Dr. Eleanor Kellon, a staff veterinary specialist for Uckele Health & Nutrition, has been an established authority in the field of equine nutrition for over 30 years. The owner of Equine Nutritional Solutions in Robesonia, Pa., she is a founding member and leader of the Equine Cushing’s and Insulin Resistance (ECIR) group, whose mission is to improve the welfare of horses with metabolic disorders via integration of research and real-life clinical experience. Prevention of laminitis is the group’s ultimate goal.

Click here to read Part 2 of the Dec. 1, 2019 installment: How can I help my 7-year-old insulin-susceptible mare lose some weight?

Click here to read more installments of Hoof Nutrition Intelligence.