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Some Hulls Are Super Feeds for HorsesBy Kentucky Equine Research Staff · January 10, 2012

“I’m paying good money to give seed hulls to my horse? What is this stuff, anyway?”

Horse owners who read feed tags may be surprised to find the hulls of soybeans, rice, peanuts, or almonds as constituents of the horse feed they are buying. While our initial reaction may be that the hull is something to be discarded and which we would rather not see in our horse’s feed, some seed hulls are valuable ingredients, while others are inert filler or carriers and some can actually pose a health hazard.

Soybean hulls and almond hulls, unlike peanut hulls and rice hulls which are virtually indigestible, are nutritious, highly digestible fibrous feed ingredients, and a valuable addition to horse feeds. Like beet pulp, they are known as super fibers because, unlike many other sources of fiber, the horse can derive significant amounts of energy from digestion of these products due to their above average digestibility.

The seed coats of soybeans are called hulls. The hulls are very much like the thin, skin-like structure that surrounds peas. Soy hulls are quite different than soybean pods, which are typically left in the field following harvest. Hulls are separated from the soybeans during oil extraction. Following separation, the hulls can be toasted, ground, and blended with soybean meal. Soy hulls are low in lignin (indigestible fiber) and are therefore more digestible than hulls from other grains or seeds.

Less popular than soybean hulls, almond hulls are more commonly used in areas where almonds are produced. The hull is the thin brown covering of the almond kernel, not the hard shell of the almond. Before they are dried, almond hulls are similar in texture to the edible fleshy portion of a peach that surrounds the stone. Once dehydrated, the hulls are as fibrous as high-quality grass hay. Although they are more often used in cattle feeds (both dairy and beef), almond hulls can also have a place in horse rations.

Feeding trials with horses have shown almond hulls to be a palatable product. While the chemical composition may vary with the almond variety, almond hulls may contain 10 to 24% crude fiber, with neutral detergent fiber ranging from 10-15%. Their digestible energy content has been described as similar to high quality alfalfa (lucerne), or up to 70% of that of barley. The product has an acceptable 2:1 calcium to phosphorus ratio and, compared to grains, these hulls have more fiber and fewer nonstructural carbohydrates. As such, almond hulls are a relatively safe feed ingredient.

Rice hulls and oat hulls are other commonly encountered fibrous ingredients which are both virtually indigestible by the horse. Rice hulls, because of their inert nature, are usually incidental ingredients since they often serve as a carrier for vitamins which are then added to fortify the feed. Oat hulls, however, may be added to boost the crude fiber content of a feed, but this should not be confused with digestible fiber.

Peanut hulls are an ingredient that is more likely to be found in feeds produced in peanut-growing regions. Like rice hulls, peanut hulls confer added crude fiber but are very indigestible. Additionally, peanut hulls carry the increased risk of aflatoxin contamination.

In general, if a variety of seed hull is also promoted as being a good choice for bedding, it isn’t likely to be a nutritious addition to your feed.