Zinc (Zn) is an important component of more than 100 enzymes. Absorption is relatively low, 5-10%, varying with the zinc status of the animal. Deficiency may lead to reduced appetite and growth, increased frequency of developmental bone and joint diseases, and a weakened immune system.
Horses are tolerant to high amounts of zinc, but a high intake of zinc may interfere negatively with the absorption of copper, and thus lead to copper deficiency.
Grass hay typically contains 15-30 mg zinc/kg and grains about the same. Commercial concentrates for horses are usually fortified with additional zinc. The requirement for zinc is set to 40 mg/kg dry matter in the ration for all categories of horses.