For horses consuming forage-only diets, a trace-mineralized salt block with iodine is an easy way to encourage sufficient intake.| Photo: Thinkstock

When we think of iodine, most of us think of the dark yellowish-brown liquid in the first-aid kit we might use to treat our horses’ wounds. Indeed, povidone-iodine is a common skin antiseptic. But iodine (I) itself is actually an important trace mineral in the horse’s diet.

Iodine is concentrated in the thyroid gland, located next to the trachea and behind the larynx (voice box). It is essential for the production of the thyroid hormones thyroxine (T4) and triiodothyronine (T3), which regulate the body’s metabolism.

Requirements & Sources

According to the National Research Council’s Nutrient Requirements of Horses (NRC), 2007 edition, an average mature 1,100-pound (500-kilogram) horse requires a minimum of 3.5-4.5 milligrams of dietary I per day, depending on exercise regimen and breeding status