Good quality grass pasture is an excellent source of vitamin E in all natural forms. | Photo: Photos.com

Q: I would like to know more about supplementing horses’ diets with vitamin E. Is it something that benefits all horses, or will green grass and sunshine be enough? Would a high-level performance horse benefit from additional vitamin E? Along that line, I often see vitamin E supplements that contain selenium. I live in an area where selenium is already added to complete feeds. Would it be safe to feed two selenium sources? —KS, via email

A: Vitamin E is a term used to describe a group of compounds known as tocopherols and tocotrienols. In equine nutrition we pay most attention to alpha-tocopherol. Alpha-tocopherol plays an important role in something called the glutathione pathway, which protects cells from oxidative damage, as well as reacting with free radicals produced by processes such as the lipid peroxidation chain reaction. However, other forms of tocopherol, such as gamma tocopherol, have unique and potentially equally important functions. At this time, though, the data on their specific roles and importance are limited.

Free radicals cause damage in cells because they have an odd number of electrons, which gives them an unstable electrical charge. In an attempt to become stable they “steal” electrons from other molecules. This causes a new molecule to be unstable, and it might not be able to perform its function within the body. A chain of oxidative destruction can result within the cell, which can negatively impact cell function and potentially cause cell death. Free radical formation is a natural consequence of various molecular processes within the cell, and we often hear it referred to as “oxidative stress.” It’s easy to label free radicals as “bad,” but they are, in fact, a perfectly natural consequence of the body using fats and carbohydrates for energy