Finding Fiber in Horse Feeds

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Finding Fiber in Horse Feeds

Beet pulp has an ADF value of less than 28%, making it a very digestible fiber source and a useful supplement to hay or pasture for any of several circumstances.

Photo: The Horse Staff

For the vast majority of horses around the world, pasture grasses and hay (dried grasses and legumes) are the most common sources for that all-important fiber fix, and rightly so, because horses have evolved to eat these plants.

The fiber content of pasture and hay can fluctuate according to the environment, time of year, soil, and stage of growth of the plants. Early spring pasture, with its tender young grass shoots, tends to be high in soluble fiber and low in lignin.

Later in the summer the grasses are tougher and less “rich.” Likewise, hay cut early in its growth cycle, before it has developed seedheads, tends to be lower in overall fiber than hay cut late; but early cut hay also is proportionately lower in lignin and higher in digestible fiber. Once the plants have gone to seed, their stems tend to become tough and fibrous, and palatability and digestibility plummet.

By contrast, the fiber content of most grains doesn’t vary a lot. Regardless of the stage of a plant’s growth, you can pretty much depend on the fiber values of grains to be within the estimated ranges in the chart below:

Representative Fiber Values for Common Horse Feeds

Feed Crude Fiber (%) Acid Detergent Fiber (%)
Alfalfa, early hay 23 28.6
Alfalfa, late hay 30 e39.5
Barley 6 7.2
Beet pulp 20 22-23
Bran, rice 13 13.1
Bran, wheat 10-12 13-15
Clover hay 21-31 32-36
Corn 2.5 3.4
Corn cobs, ground 35 42
Grass hay, early 31-34 31.4
Grass hay, late 31-35 41.6
Molasses 0-0.5 0.1-0.2
Oats 11-12 13.5-14.6
Oat hay 32 36.4
Oat hulls 33-36 40-44
Sorghum/Milo 2.8 5.9
Soybean meal (44%) 7 10

As a result, most horse owners can rely on the information on the feed tag and forego getting a fiber analysis of their grain ration. But doing an analysis of your hay (and/or pasture) can be valuable, especially as similar-looking batches of hay can be remarkably different in fiber content.

The best way to sample hay is by using a corer on several bales (your local Extension agent might be able to help you obtain hay samples). Insert the corer diagonally along the long axis of each of the bales rather than straight through the center, and take samples from at least 20 bales, ideally, mixing them together in a clean paper or plastic bag. If you don’t have access to a corer, you also can get good results by doing a “grab sample,” taking a handful of hay from 20 bales, each from different parts of the hay field. Make sure to get some from the center flakes and some from the ends to get a real mixture. The proportion of leaves to stems can make a big difference to the resultant acid detergent fiber (ADF) and neutral detergent fiber (NDF) values, so make sure that you have not grabbed too much of one and not enough of another. Most labs can return results within a week or two at a fairly low cost.

If you want to get a fiber analysis of your pasture, first use a bit of observation. There is no point in analyzing the fiber content of plants your horses don’t eat, so begin by watching them to see which plants they favor. Then take handfuls of only those plants from several locations throughout your field.

How do you interpret the results? As a rough guideline, forage with an ADF value of more than 35% is considered poor quality and probably is past bloom. Its digestibility will be low—which is not to say that it cannot be fed, but that you will have to feed considerably more of it for your horses to extract the same quantity of nutrients they could glean from a “younger” forage. (It’s interesting to note that donkeys, which are adapted to living in harsh conditions, are considerably more efficient at extracting nutrients from poor-quality, highly indigestible forages than are horses and ponies.) Acid detergent fiber is considered a good overall parameter for assessing the maturity of forages.

Hay and pasture grasses are not the only fiber sources available to horses. One of the most popular alternatives is sugar beet pulp, a feed additive made from the fibrous portion of the sugar beet after the sugar has been extracted. Available in North America almost exclusively in a dehydrated format (either shredded or in pellet form), beet pulp can be rehydrated by soaking it in water for a few hours before feeding. 

Beet pulp has an ADF value of less than 28%, making it a very digestible fiber source and a useful supplement to hay or pasture for any of several circumstances. When beet pulp is soaked, its soft texture is easy to chew, making it a good choice for older horses or any animal with a dental problem. It also is favored for putting weight on “hard keepers,” and it makes a convenient place to hide oral medications. Many horse people also serve it warm on cold winter nights, though one suspects that the comforting effect of such a meal does more for the owner’s psyche than for the horse. Because the crude protein content of beet pulp is fairly low (averaging around 8%), it is appropriate for almost every type of horse. It is also fairly high in calcium.

Bran, another traditional way of supplementing fiber, is a less suitable choice. Bran is the grain kernel’s outer layer that is removed in the process of milling. Wheat bran is the type most commonly fed to horses (though rice bran is sometimes used as a fat supplement in small quantities). A fluffy, low-density feed, bran is only half as dense as (and thus delivers only half the digestible energy of) oats and only a quarter as dense, and energy rich, as corn or barley. So despite its ADF of approximately 15%, it takes a lot of bran to provide sufficient fiber for the average adult horse.

Furthermore, its purported laxative effect has been shown to be a myth. Whether fed dry or wet, bran has no demonstrated “loosening” or “regulating” effect on the bowels. (The loose manure many owners observe after the feeding of a weekly bran mash is, in fact, the result of a mild digestive upset from a sudden change in the diet.) An occasional small bran mash probably does no harm, but as a fiber supplement, there are better choices. If you must feed bran, make it no more than 10% of your horse’s total ration.

Two other fiber supplements are lignin-rich and largely indigestible. They are added to the diet mostly as “busy food”—useful in keeping obese or idle horses chewing away—and, to some extent, to aid in digestive health by keeping gut motility up to speed. Chaff (chopped straw or low-quality hay) is a feed additive mixed in with grain that is often used in the United Kingdom. Chaff helps to slow down a horse that bolts its feed, to “fake out” an overweight or greedy horse that would like to be getting more grain than he needs, or to “cushion” the system of a horse with a tendency to colic. Oat straw and barley straw are commonly used to make chaff, and while their ADF values are usually more than 35%, they are certainly harmless even if they provide more bulk than nutrition to the diet.

Grain hulls are another inexpensive way to provide that same effect. High in crude fiber (up to 50% higher than grass hay) and low in energy, hulls can be used to replace some or all of the forage in a horse’s diet. The hulls of most cereal grains can be fed safely to horses. Oat hulls are particularly popular, and coarsely ground corn cobs are another similar product. There is one caveat: Because hulls are often ground, they tend to be dusty. Blending them with a little water or molasses can help keep the dust down, or you can buy a pelleted version.

One downside to most of these alternate fiber sources is that the horse can consume them far faster than he can consume hay—so any time you substitute another fiber source for forage or pasture, you could be giving your horse less opportunity to satisfy his compelling urge to chew (which is part and parcel of his herbivorous nature). Boredom can translate that urge into stable vices, coprophagy (eating manure), even munching on the stall walls or his neighbor’s tail.

Feeding small meals often (at least three to four times a day) is a partial solution. But under most circumstances, forage is still the best and most natural choice for most horses. Other fiber sources can be used as supplements to hay or pasture, or as a complete substitute only in cases such as advanced respiratory disease (i.e., heaves) or dental problems that make it impossible for the horse to chew and process forage.

About the Author

Karen Briggs

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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