Grains of Glory

It's five p.m., and up and down the aisle of a large boarding stable, the nickering and rumbling begin. What's the cause of the excitement? Nothing more than a metal scoop digging into a bin of grain, a sound that tips off every equine resident that it's dinner time. Hay seldom receives this sort of reception, of course--it's grain that horses really relish.

But just because horses love their grain doesn't mean that it's an essential part of their diet. Quite the opposite, in fact. Horses evolved as grazing animals, with digestive tracts designed to draw nutrition from tough, fibrous, gritty prairie grasses. In the wild, horses only encounter grain as an occasional plant seedhead--certainly never in the volumes found in their feed buckets in a domestic scenario. And while their teeth can grind grain seeds quite efficiently, their digestive systems are poorly equipped to deal with the low-fiber, high-carbohydrate wallop that grain delivers--thus the much higher incidence of colic among grain-fed horses versus those fed only forage.

So why feed grain? Chiefly, to provide more energy for the work we ask of our performance horses. Forage alone provides enough energy and nutrients for maintenance metabolism--grazing, sleeping, wandering from pasture to pasture, and the occasional burst of speed to escape a predator--but for the vast majority of horses, it fails to measure up to the demands of the sustained (and occasionally strenuous) exercise we ask of them. The higher digestible energy (DE) content of cereal grains picks up the slack.

Although grains in their natural state supply very little in the way of vitamins (commercially mixed rations generally are supplemented), they do provide an important mineral that might be lacking in the diet of a horse on a forage-only diet: phosphorus. Hay provides high amounts of the macromineral calcium, but an inadequate amount of phosphorus. Both of these minerals are crucial to correct bone and muscle development and maintenance, and the ratio between them in the horse's diet is pivotal.

The ideal ratio is between 1:1 calcium to phosphorus, up to about 1.8:1 calcium to phosphorus. Too little phosphorus means bone-building and repair are not carried out as they should; too much, and the whole system is out of balance and seeks to re-establish itself by leaching existing calcium out of the bone, eventually causing bone abnormalities. So grains, which are generally high in phosphorus and low in calcium, can make a perfect companion to hay because, when both are fed in the correct quantities, they provide an almost ideal Ca:P ratio for the horse.

Inside Grain

The grain contained in a feed bag actually is the seedhead of the plant, containing the nutrient store for the germ (embryo) from which a new plant develops. It consists of a coat, a starchy endosperm, and the germ itself. Some grains, such as barley, rice, oats, and husked sorghum (milo), have a fused husk or hull, which provides extra fiber; others, such as corn, wheat, rye, and millet, do not.

The grains that are fed to horses vary a great deal from continent to continent. In North America and parts of Europe, oats and corn are the most common, but milo (sorghum) is commonly fed to all types of livestock in Central America, and wheat (despite its low palatability) is popular in many parts of the world. Even relatively obscure grains like triticale, spelt, and emmer have found their way into the diets of horses. Regardless of the species, all of these grains have some characteristics in common: They are four to eight times as heavy as baled hay (per unit of volume); they're low in fiber and about 50% higher in dietary energy than average-to-good quality hay; and starch makes up 55% or more of their total dry matter.

Starch digestibility by the horse is quite high--estimates range from 87% to nearly 100%--and therein lies a problem. When a grain meal hits the horse's small intestine, some of the starch is digested and absorbed as glucose, but the rest, instead of passing through the system undigested, is converted by the microflora in the cecum to volatile fatty acids and lactic acid. If the production of these acids is rapid enough (as often happens when a large quantity of grain is fed at one time), cecal acidosis can result--a condition which can trigger diarrhea, colic, and laminitis.

To reduce the risk of this reaction, it's wise to follow the old horseman's credo of "small meals, often." This gives the small intestine time to process the starches before the system moves everything along to the cecum--and the more starch that gets digested in the small intestine, the less cecal acidosis results.

Because forage in the system can decrease the amount of grain processed in the small intestine, it's best not to feed hay for an hour or more before feeding grain, or for three hours or more after feeding grain--a rule that definitely was not in the old horseman's lexicon. Other approaches that can help include giving preference to fiber-rich grains with hulls, such as oats, or choosing grains that have been processed by grinding or heat treatment (more on this later) to improve the digestibility of the starches.

Regardless of whether you follow these guidelines, however, the intake of an excess quantity of any type of grain can result in dire consequences--such as life-threatening colic or founder. Unfortunately, equines have no dietary wisdom when it comes to grain, and given the opportunity to gorge themselves (for instance, if the feed room door is left open), they can conceivably eat themselves to death. Because of this, grain never should be fed free-choice or left so that it is accessible to horses outside of their allotted amount at mealtimes. And except in some very specific circumstances (largely with horses in hard race training), the grain portion should never be more than 50%, by weight, of a horse's total daily ration. It need not be fed at all, in fact, unless you wish to supplement the energy or nutrient requirements of your equines beyond what their forage provides. A good many pleasure horses, especially those who are "easy keepers," do very nicely without the addition of grain to their diets.

Grain Types

Of the grains commonly fed to horses, oats (Avena sativa) are the traditional favorite, reported to make up more than 30% of all commercially prepared horse feeds. The same quality that makes them such a popular feed for horses is responsible for their being less favored for other livestock--oats have a low energy density compared to most other grains. That's a result of the fibrous hull, which makes up a significant portion of the oat seed and makes oats a "safer" feed for horses (less likely to cause cecal acidosis because of a lower starch content) than hull-less grains such as corn and wheat.

Horses also seem to prefer oats over most other grains, making them a close second in the palatability sweepstakes to molasses-laced sweetfeeds. But oats tend to vary more in both quality and price than most other grain crops, and the yield per acre is relatively low. Their popularity with owners and trainers, in many cases, seems to have more to do with habit, and a lack of familiarity with other cereal grains, than anything else.

Because oats have a relatively soft kernel, most adult horses have no difficulty chewing and digesting them. Oats can be "clipped" (a process in which the pointed top and tail of the grain are clipped off), "crimped" (lightly crushed so as to crack, but not completely remove, the hull), or rolled (flattened, as when processers make oatmeal), but these processing techniques rarely are needed to make oats a good horse feed, except in the case of very young or very old equines, or those with tooth problems.

Oats have the advantage of being less vulnerable to molds and mycotoxins than most other grains. But because of their relatively small growing area (they grow best in cool weather, limiting their cultivation to the Northern United States and Southern Canada) and low yields, oats are becoming less and less popular as a major crop--which means that oats are more expensive than other grains, and are likely to become more so in the future.

It pays to shop for good-quality, "heavy" oats (often called "racehorse oats") because they contain less foreign material and weigh more per unit of volume. The individual grains should look plump, light blonde in color, and fairly uniform in size. Slimmer, light-weight oats can provide the same nutrition, but less value for your dollar.

Dehulled oats, sometimes called groats, are an alternative feed sometimes available for horses; they provide more digestible energy per pound, but lack the safety margin that the oat hull provides. That, coupled with the high cost of processing the grains this way, makes groats a far less-popular feed for horses than they were in the past.


Corn (Zea mays), or maize as it's known in many parts of the world, is probably the second-most familiar grain for horses, and overall as a livestock feed, it is the leading crop in the United States. It constitutes more than 80% of the grain fed to animals in North America, and its production continues to rise. Most horses find it only slightly less palatable than oats, and more tasty than many other cereal grains, and it is a good-quality and nutritious grain for horses.

Because corn is a hull-less grain, however, it is very high in starches--fiber makes up only 2.2% of its total composition, and its digestible energy value is more than twice that of oats. This means that it does not have the "safety margin" that oats enjoy, and it must be fed with caution and in relatively small quantities. (Many nutritionists recommend against corn's being fed as the sole grain for this reason, suggesting that it is better mixed with other grains to balance its high starch concentration.)

Corn's reputation for being a feed that makes horses "hot" and hard to handle is largely mythical; it stems from owners who have carelessly substituted corn for an equal quantity of oats in their horse's diets--unwittingly supplying more than twice the energy! Feeding by weight, rather than by volume, is crucial when switching grains.

The hardness of the individual kernels means that in order to be digested well by the horse, corn usually needs to be processed, by cracking (breaking each kernel into pieces), or flaking (flattening individual kernels with a roller). That processing increases the utilization of the grain, but also exposes it to the possible growth of molds and mycotoxins, which can cause aflatoxicosis and moldy corn disease (both potentially fatal if ingested.) Of all the cereal grains fed to horses, corn is the most likely to be contaminated by molds, particularly if poorly stored (in very damp, humid, or hot conditions.) Because of this, any corn that is even remotely questionable never should be fed.

But contrary to popular belief, corn is not a "heating" feed in the traditional sense. In fact, because the greatest amount of internal heat in the horse's body is generated through the microbial fermentation of fiber, not starches, increasing the amount of hay in your horse's diet in winter will generate more body heat than will increasing the amount of corn he eats. However, because corn provides lots of energy per pound, and energy needs increase during cold weather, corn is a good winter feed for horses.


Very popular in the United Kingdom and Europe as a horse feed, barley (Hordeum vulgare) doesn't enjoy the same favoritism on this side of the Atlantic. But it has a long and honored history on the equine bill of fare, even reputed to have been the staple diet for the early Arabian herds who were the foundation for so many modern horse breeds. Today, it's the most widely cultivated cereal grain in the world, needing a shorter growing season than corn and tolerating limited rainfall well. Over half of the world's harvest of barley comes from Europe and the former Soviet Union. In the United States, about half of the total barley crop (only about a twentieth of the corn harvest) is fed to livestock, with another 25% going towards alcohol production.

Barley grains resemble smallish oats, but are somewhat harder; because of this, they are usually rolled or crimped when fed to horses. (In the UK, it's common to cook the barley grains, making the starches more digestible and the meal far more palatable.) Processed barley can be dusty, and if finely ground, the end product, which is heavy and low in bulk, can tend to pack in the stomach and present a colic risk. For this reason, when barley is fed as the principal grain, it's often mixed with a fibrous product such as chopped hay or straw (chaff) or beet pulp to keep the digestive system moving. It's also used as a major component in commercial pelleted feeds.

Like oats, most types of barley contain hulls, providing the grain with a higher fiber content than corn, but lower than that of oats. In fact, barley could be described as an "in-between" grain in many ways: Supplying more digestible energy and total digestible nutrients (TDN) than the same quantity of oats, but not as much as corn; and between oats and corn in terms of fiber content and "safety," as well as heat produced in its digestion. However, it is slightly higher in protein than either oats or corn (making it a good choice for breeding stock and young horses), has a very high phosphorus content (so high, in fact, that it is undesirable as a single grain even when fed with high-calcium alfalfa to balance it out), and less of its starch tends to be processed in the small intestine, increasing the risk of cecal acidosis. In addition to all this, barley is less palatable than oats and corn, and it is most commonly used not as a single grain, but in a grain mix with oats, corn, and frequently molasses.


About 6-8% of the grain fed to livestock in the United States is sorghum, or milo (S. vulgare). It can be a good feed for horses, although its feed value varies depending on its tannin content. Tannins provide a degree of resistance to mold, but decrease milo's protein digestibility and palatability, as well as giving it an astringent taste. Brown milo, which has the highest concentration of tannins, is not a suitable feed for horses because of this. (Unfortunately, yellow milo, the preferred variety, often is visually difficult to differentiate from brown.)

Milo has a small, hard kernel, and for efficient utilization by horses, it must be steam-flaked. Whole grains, or even those that have been dry rolled, are too difficult for horses to chew and digest. Like corn, milo is high in energy density and low in fiber, so it must be fed with caution.


Wheat, rye, and even hulled rice can be used in a horse's diet in addition to the grains described above, but they seldom are fed in North America, usually because their palatability is low or because their cost and/or availability are prohibitive. They occasionally make an appearance on the feed label of a commercially mixed ration, however, where a dash of molasses can improve many a taste factor!

Processing Grains

Processing grains can markedly improve their digestibility, but it is not without its disadvantages. Chief among these is the fact that when you break the hard seed coat that is the seed's natural protection, you make it vulnerable to invasion from microorganisms as well as insects. You also open the endosperm to more rapid nutrient breakdown upon exposure to the elements. At the very least, breaking open the kernel exposes the grain to oxidation, causing a stale flavor that quickly decreases its palatability. (Some feed companies apply antioxidants and mold inhibitors to their processed grains to combat this.) Grains that have been crimped, rolled, steamed, or otherwise processed must be stored for much shorter periods than whole grains, and must be watched closely for signs of mold.

In the case of oats, no increase in feeding value has been noted for processed (crimped, rolled, or steam flaked) oats versus whole grains--and most nutritionists recommend that oats only be processed for those horses with dental problems. In the case of harder grains, such as barley and corn, processing can provide significant advantages in terms of the amount of starch digested in the small intestine (as opposed to the cecum), and can reduce the risk of diarrhea, colic, and founder. For small, hard grains, such as milo, rye, and wheat, processing is essential for horses to extract any nutrient value.

Methods of processing can include cracking and rolling of the dry grains to varying degrees. They should not be finely ground, as this decreases palatability and increases the dustiness of the ration; in addition, some researchers suspect it can contribute to gastric ulcers as it does in pigs. In any case, the utilization of finely ground grain is no better (and possibly worse) than more coarsely ground kernels. Larger pieces of the individual kernels also make it easier for the consumer to assess the quality of the grain.

Heat processing, which can include steam-flaking, micronizing, pelleting, and extruding (or "popping"), almost invariably makes grain more expensive, but it also offers some plusses. Studies have shown that protein utilization from oats and milo is 2-3% higher when those grains are micronized (cooked with dry-heat microwaves), and starch digestion of corn in the small intestine can be improved by almost three times when the grain is extruded. In addition, most horses show a marked preference for processed grains over unprocessed ones, in the case of every grain except oats.

Which to Buy?

Although all of the grains discussed here can have a valuable place in your horse's diet, no single grain will provide all the nutrients a working horse needs, even when fed in combination with premium-quality hay. Of all the grains commonly fed to horses, oats generally are considered the closest to the "perfect" feed...but even oats fail to supply sufficient quantities of many vitamins and minerals, and their relative energy density is low (which as we know makes them a safer, but more expensive, feed pound per pound).

This is where commercially balanced rations offer a tremendous advantage. Formulated with a mix of grains, and generally supplemented with a mixture of vitamins and minerals appropriate to the type of horse for which it is designed (i.e., performance horses, breeding stock, or growing youngsters), a commercial ration provides what no single grain can: balanced nutrition. You can, of course, also do your own calculations and create your own balanced feed from a mixture of grains, but the math sometimes can be daunting, and the results varied, depending on your understanding of nutrition. However, it's comforting to know that from crop to crop, the nutrient values listed in charts like the one on page 62 are far more reliable for grain than for hay (the content of which can fluctuate wildly depending on the soil, growing conditions, and season). If you are interested in formulating your own ration, consult your feed company's equine specialist or your state extension specialist (whom you can locate by contacting the nearest university with an agricultural college); he or she can help provide you with reliable information on how to tailor a grain ration to your horse's needs.

Whenever you're buying grain, keep in mind that if it doesn't look palatable to you, you probably don't want to feed it to your horses. Buy only the best-quality grain you can afford, buy it in small quantities whenever possible to ensure its freshness, and store it properly to prevent it from becoming contaminated (more on storage techniques next month).

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.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More