Iodine (I) is required for the formation of thyroid hormones (thyroxine) which control the metabolic rate of all animals. Iodine deficiency leads to goiter and reduces metabolic rate.
Foals born to mares with iodine deficiency or a deficient supply of iodine may be weak or stillborn.
Good sources of iodine are seaweed, fishmeal, commercial concentrates (where iodized salts are commonly used) and common mineral mixes.