Many nutrients affect hoof quality: proteins and specific amino acids such as methionine; minerals such as calcium, iron, sulfur, iodine, zinc, and selenium; and vitamins such as biotin, vitamin A, and vitamin E. Each of these nutrients plays a role in sound hoof growth.
In fact, healthy hooves cannot be grown without proper levels of all nutrients. The key to an effective hoof supplement is delivering the critical nutrients that may not be adequate in the diet. Several of these nutrients, including zinc, biotin, and methionine, have been the focus of research trials.
The specific nutrients to look for in a quality hoof supplement would be biotin (at least 15 mg per serving), zinc, methionine (or zinc methionine complex), and iodine. Some horses respond to supplementation of one nutrient while others respond to another nutrient, so a combination of nutrients would be best for a general hoof supplement. Some hoof supplements have a multitude of additives other than those that research has shown to help hoof health.
Care should be taken with these if used in combination with other vitamin or mineral supplements to prevent dangerous over supplementation of nutrients.