Common ingredients used in grain-free diets to increase the feed’s calorie level include wheat middlings; fermentable fibers, such as sugar beet pulp and soy bean hulls; and fat sources such as rice bran and vegetable oil. | Photo: The Horse Staff

Q.I have an ulcer-prone mare that I’ve always fed a forage-first diet with a vitamin supplement mixed with hay pellets. When I’ve fed concentrates in the past, she’s developed gastric ulcers. Now I’ve started training her for endurance and feel she needs more calories for this higher-intensity work. I’m curious about grain-free feeds for horses. What does grain-free mean? Does it mean low-starch? If they aren’t providing calories from grains, where is the energy coming from?

—Via e-mail

A.The Association of American Feed Control Officials defines grain as seed from cereal plants. For example, oats, barley, corn, and wheat—in their intact forms—would be classified as grains as they are all seeds from the respective plants. Wheat middlings, however, would not be classified as a grain as it is not the whole seed. Rather, “middlings” is specifically a term used to describe “a by-product of flour milling comprising several grades of granular particles containing different proportions of endosperm, bran, (and) germ, each of which contains different levels of crude