Ask any Average Joe on the street what a horse eats, and chances are he’ll answer, ‘hay.’ Even those who’ve never picked a foot or mucked a stall recognize that fibrous dried forage as the foundation of a horse’s diet. Given that, it’s surprising how little respect hay gets. Perhaps it’s not as sexy as a bag of high-powered grain or a bucket of space-age supplements, but without hay, we couldn’t maintain our horses in good health.

Although horses were designed as grazing animals, there are very few places in the world where good-quality pasture grows year-around. In climates that suffer ice and snow in the winter months, pasture plants wither and die. In warmer zones, hot summer days can cause pastures to go dormant from lack of moisture. Either way, you’re looking at months of poor grazing, during which, if left to their own devices, most horses would suffer weight loss and nutritional deficiencies. Fortunately, hay helps fill the gap, and in many situations, it provides the bulk of the fiber in an equine’s diet even when grazing is available.

Lower in moisture than fresh plant material, hay provides concentrated fiber in a format that demands a lot of ‘chew time.’ That’s beneficial because a horse who’s munching hay is having his grazing urge satisfied (and as a side-benefit, he’s not chewing down your barn or fence). Hay also helps maintain your horse’s gastrointestinal health. Because the gut is designed first and foremost to process fiber, its activity and muscle tone are stimulated by digesting hay. Too little fiber in the diet can put your horse at risk for dehydration, colic, and even laminitis.

Since hay is such an important part of your horse’s diet, it’s worth digging into a bale to find out more.

FAQ: How much hay does my horse need?

As a rough guideline, a horse should consume 1% to 2% of its body weight each day in forage products—at least 50% of the total diet under all but the most extreme exercise programs. For the vast majority of adult horses, that percentage can be pushed up considerably higher—even to 100%—if the horse is an easy keeper and/or not being asked to work. The basic principle is this: grain is an optional part of a horse’s diet. Roughage (fiber) is not.

Although all of us prefer to feed by ‘eyeballing’ amounts, the weight and size of a flake of hay can vary so much that it is worth weighing the flakes to determine how close you are to these guidelines.

FAQ: What nutrients does hay provide?

Hay generally is high in calcium and low in phosphorus. It contains high levels of potassium and vitamins A, E, and K. If hay is sun-cured, it also has high levels of vitamin D.

Hay can be extremely variable in protein content. Legume hays (such as alfalfa or clover) might contain 20% or higher crude protein, while grass hays (such as timothy, Bermuda grass, or orchard grass) average about 11-14% protein, and can dip as low as 4%. The protein content of hay is largely determined by the time in which it is cut—the younger the hay, the higher the protein. Hay cut past the mid-bloom stage (when about 50% of the plants have flowered and gone to seed) is a good deal lower in protein content, and mature (full-bloom or past-bloom) hay might be inadequate to meet an adult horse’s nutrient requirements.

FAQ: How does a horse digest hay?

Equines can’t digest fiber on their own. They lack the enzymes needed to break the bonds of the polysaccharide fibers contained in hay, so they can’t extract the nutrients from the plant material. Fortunately, horses (like most other animals) have a population of beneficial intestinal bacteria living in the cecum (part of the large intestine). They are specially adapted to digest the fiber that horses cannot. Through a fermentation process, these gut ‘flora’ produce the necessary enzymes to convert fiber to volatile fatty acids (VFAs), which horses can absorb. Not only do the bacteria benefit (making this a truly symbiotic relationship), but the VFAs they create provide between 30% and 70% of the horse’s total digestible energy needs.

FAQ: What kinds of hay are there?

The two types most people are familiar with are grass hays and legume hays. Of the legumes (a catch-all term describing a family of plants that have nitrogen-producing root nodules), alfalfa is the most popular crop. It’s estimated that more than half of the hay harvested in the United States is alfalfa, or an alfalfa/grass mix. Other types of legume hay include clovers (red, crimson, ladino, and alsike are a few), birdsfoot trefoil, and lespedeza. Legumes tend to be more nutrient-dense than grasses. They contain two to three times the protein and calcium, as well as more soluble (non-fibrous) carbohydrates, beta-carotene (the precursor of vitamin A), and vitamin E. In addition, they’re very palatable—in a ‘taste test,’ most horses will choose legume hay over grass hay. Because of these qualities, they’re the preferred hays for young, growing horses as well as lactating mares. Their high protein content makes them less appropriate for mature horses not being used for breeding. In addition, legumes generally are more costly, and in some areas of North America can be infested with deadly blister beetles.

There are a surprising number of different varieties of grass hay, with timothy being the most widely grown across North America. Timothy is an easy crop to establish on most soils, and it tolerates cold well, sprouting early in the spring, weeks before most other hay crops. Timothy doesn’t cope well with extremes of heat and humidity, so in the central and southern United States, growers might turn to alternatives such as quick-curing Coastal Bermudagrass (a variety developed to grow tall enough to harvest as hay), brome (drought-resistant, hardy, and cold-tolerant, but less palatable than some other grasses, and so usually grown in combination with alfalfa), or orchardgrass (a very drought-resistant species that can be productive even on poor soils). Bluegrass, fescue, reed canarygrass, ryegrass, and Sudangrass are some of the other varieties of grass hays fed to horses. Grass hays don’t harbor blister beetles, and they often are less dusty than legume hays, making them a preferred choice for horses with respiratory problems. Their more modest protein content makes them a better choice than legumes for mature horses.

FAQ: How can I tell a grass hay from a legume hay?

You can distinguish the two by looking at the stalks and leaves: Grass hays grow tall, upright stalks and long, slender leaves that sheathe the stalk itself, rather than branching out on stems the way legume leaves do. Legume stalks often are coarser (which can make them prone to incomplete drying and, as a result, mold). Grass hays develop seed heads, which can be examined to help determine the maturity of the hay (the larger the seed heads, and the greater their frequency in the bale, the older the plants were at harvest). The structure of the seed heads can vary from the cattail-like structures of timothy to the branched, tree-like fronds of bluegrass and orchardgrass.

FAQ: What is a ‘mixed hay’?

Mixed hay is a combination of legumes and grasses. There are considerable advantages to growing these plants together as one crop. First, horses consider legumes tops in palatability, so picky eaters who turn their noses up at straight grass hay might consume a flake if it contains some legumes as well. Second, a lower-protein grass hay might help balance the high protein level of a legume and create bales that are appropriate to feed to mature horses. Third, the addition of nitrogen-producing legumes to a grass hay crop actually helps fertilize the field and increases the yield of the grass hay. In many parts of the continent, mixed hay is the preferred feed for horses, although the mix might be any of a number of combinations of legumes and grasses.

FAQ: Is the nutrient content of hay the same as fresh grass?

No, because the process of harvesting and storing hay takes its toll. Even under the best conditions, hay suffers losses of 30-70% during the harvesting and baling processes, with legumes taking the brunt of the damage. Losses from normal respiration account for about 5% or 6% of the total dry matter (and that number can rise if the humidity is high). Another 10-25% might be lost in raking and baling. Legume leaves, in particular, can fall to the ground as they dry, and high leaf loss can significantly compromise the nutritional value, and therefore the quality, of the hay. The leaves of a legume contain about two-thirds of the digestible energy, three-quarters of the protein, and most of the other nutrients.

Long-term storage also has an effect on the nutrient content of your hay. Over time, vitamins tend to break down, especially if the hay is exposed to light. It’s estimated, for example, that vitamin D in hay degrades at a rate of about 7.5% per month, so hay that is a year old or more might no longer meet your horse’s vitamin D needs. Vitamin E is even more fragile; from 30-80% of its activity in hay is lost during the process of cutting and baling. (Fortunately, most commercial grain rations are fortified with vitamin E, which helps prevent deficiencies in the overall diet.)

FAQ: How can I assess quality?

Much of the assessment of the quality of your hay can be done through simple observation. Good-quality hay should be green, not yellow or brown (keep in mind that some hays, particularly some varieties of clover, can cure to an almost black color, which is not necessarily an indicator of mold growth). It should have a high leaf content , few weeds, and should smell pleasant and slightly sweet. There should be no visible mold (white or dark matted patches in the hay) or other foreign material. If you take a handful of hay and squeeze it, it should not hurt your hand—prickly hay has been cut too late and has a low nutrient content. If you drop a flake of hay from a height of a few feet, you should not see clouds of dust rising from it. Dust is usually an indicator that the grower had the tines on his harvester set too low.

FAQ: How can I tell what nutrients my hay contains?

To really determine the nutrient content of your hay, you’ll need to do a hay analysis. Appearance is a poor indicator of nutritive value. Even grass hays that appear very similar can vary in protein content by two to three times. Your state extension agent, university nutrition specialist, or local feed company should provide this service for a cost of about $20-$40, and the results can be invaluable.

Hay can be sampled either with a corer (which is inserted into several bales to draw samples), or by breaking open at least five bales and taking representative handfuls from the center and near-the-end flakes and combining them in a paper bag. A lab analysis of the hay sample can yield information such as the crude protein content, TDN (total digestible nutrients), crude fiber (CF), acid detergent fiber (ADF), calcium, phosphorus, and the all-important moisture content. You also might request other data, such as the copper or selenium content. Your feed specialist or extension agent can help you interpret the results and balance the rations in your barn to complement the nutrients in your hay.

FAQ: Why is hay such an important part of my horse’s diet in winter?

Hay is the easiest and least expensive way to provide the essential fiber in your horse’s diet at a time when he’s probably on a reduced work schedule and pasture is likely to be inadequate. Not only that, but eating hay will help keep your horse warm when the wind blows bitter. The very process of digesting hay (fermentation in the cecum) generates a considerable amount of chemical heat. The horse’s body uses that heat to help maintain internal body temperature. By contrast, digesting carbohydrates and/or fats (which happens mostly in the stomach and small intestine) doesn’t generate nearly as much heat. So if you want to help your horse keep warm in winter, don’t increase the amount of grain he’s eating; instead, provide him with more hay.

FAQ: What type of hay is best for my horse?

There are three main concerns when you purchase hay—appropriate nutritional content, quality, and palatability. Good-quality hay should be free of mold, dust, and weeds, and should not have been rained on during or after harvest. It should be sweet-smelling and appetizing. Palatability is influenced by the plants in the mix. Some types of hay are relished by horses more than other types, and depending on the climate in which the hay is grown, a hay field might contain quite a complex mixture of plants, some providing hardiness and others boosting the taste quotient. Palatability also has to do with how ‘chewable’ the hay is; late-harvested grass hays, for example, might be extremely stemmy and coarse.

The vast majority of adult horses with good dental health can be maintained well with grass hay; its lower protein content and high fiber content make it the most appropriate choice, nutritionally speaking. If what’s available is mixed hay, choose a mix that puts the emphasis on grasses (to keep the protein content on the low side) and has, ideally, been harvested at around mid-bloom. Only young, growing stock (weanlings and yearlings) and lactating broodmares really have need of the protein levels contained in a legume hay. For other horses, straight clover or alfalfa hay might actually provide something of a protein and calcium overload. One exception is geriatric horses. Because their ability to absorb nutrients, including protein, is compromised, they can better tolerate the high protein content of a legume hay, and they often find the soft texture of such forage far easier to chew than a coarser grass hay.

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 TheHorse.com. Learn More

Free Newsletters

Sign up for the latest in:

From our partners