Hay, Look Me Over

Horses are superbly adapted herbivores. From their wide flat molars--designed for grinding tough, gritty stems--to their gastrointestinal tracts--which process the nutrition bound in fibrous plants--they are equipped to get the maximum benefit out of food sources that many animals reject. Evolution also has provided horses with a talent for speed, equipped them with eyes set high on the sides of the head (the better to see approaching predators while grazing), and given them a preference for a herd lifestyle, to help survival while wandering the open grasslands that are their chief foraging habitat.

Our domestic horses don't, as a rule, have the luxury of roaming for hundreds of miles in search of choice grazing. Confined to stalls and paddocks, they rely on us to provide the forage they need. For a good part of the year, when sufficient pasture is not available in many parts of North America, that means we give them hay--grasses and/or legumes that have been sun-cured, dried, and baled for convenience.

Defining Forage

Forage is loosely defined as feed with a minimum fiber content of 18% and a relatively low dietary energy, or DE, content, made up of the stems, leaves, and stalks of plants. Forage is the most natural, least expensive, and safest feed for horses, and it should be the basis of all horse feeding programs. It provides the bulk of nutrients horses require for their everyday maintenance metabolism, and stimulates the muscle tone and the activity of the gastrointestinal tract. Horses with inadequate amounts of forage in their diets run the risk of colic and founder, as well as developing stable vices derived from having too little on which to chew.

Hay, the most common type of forage fed to horses, averages 28-38% crude fiber, and has a DE level of about 0.9-1.1 Mcal per lb. (Cereal grains, by contrast, contain between 2-12% crude fiber, and have a much higher DE, averaging 1.5-1.7 Mcal/lb.) Hay is high in calcium and low in phosphorus. (Happily, grains are generally high in phosphorus and low in calcium, so a horse being fed both hay and grain usually ingests a Ca:P ratio that balances out.) Hay also contains high levels of potassium and vitamins A, E, and K--and if sun-cured, high levels of vitamin D as well. (Vitamins tend to break down over time, so the more recently the hay was cut, the higher the vitamin content; by the time baled hay is a year old, it might contain no appreciable amount of vitamin A.)

Hay can be extremely variable in protein content. Legume hays (such as alfalfa or clover) can contain 20% or more crude protein, while grass hays (such as timothy, Bermuda grass, or orchard grass) average about 11-14% protein, and can go as low as 4%. The protein content of hay is largely determined by the time when 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 can be inadequate to meet an adult horse's nutrient requirements.

There actually are three types of hay, but one, cereal grain hay, is rarely fed to horses in North America as it is not considered economical. Cereal grain hay is hay cut from grains such as wheat or barley, while the plant is still green and before the seed is harvested. It is nutritionally similar to grass hay, and the more grain (seeds) the hay contains, the higher its nutritional value. (If the seed heads are lost in harvesting, only straw remains--which makes good bedding but a poor feed.)

Far more common are grass hays and legume hays. Of the legumes, alfalfa, also called lucerne, is the most popular crop. It is estimated that more than half of the hay harvested in the United States is alfalfa, or an alfalfa/grass mix. Other legume hays include clovers (varieties include red, crimson, ladino, and alsike), birdsfoot trefoil, lespedeza, cowpeas, vetch, and even soybeans. Legume hays almost always are preferred by horses over grass hays, and they contain two to three times the protein and calcium of grasses, as well as more soluble (non-fibrous) carbohydrates, beta-carotene (the precursor of vitamin A), and vitamin E. Because of these qualities, legume hays are preferred for young, growing horses as well as lactating mares. But legumes are generally more costly, and in some areas of North America can be infested with poisonous blister beetles.

There are also a number of different types of grass hay, with timothy being the most widely grown across North America. It is an easy crop to establish on most soils, and it tolerates cold well, actively beginning to grow early in the spring, weeks before most other hay crops. However, 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 Bermuda grass (a variety developed to grow tall enough to harvest as hay, unlike its cousin, common Bermuda, which suits better as a lawn), brome (drought-resistant and hardy, and also cold-tolerant, but less palatable than some other grasses, 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 Sudan grass are some of the other varieties of grass hays fed to horses. Grass hays not only don't harbor blister beetles, 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 not being used for breeding.

You can distinguish a grass hay from a legume 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 as do legume leaves. Legume stalks often are coarser, and the leaves are less firmly attached--which leads to increased wastage after harvest, when the dry leaves tend to shatter and crumble out of the bale. The seed heads of grass hays, however, can vary a great deal, from the narrow, cattail-like structures of timothy, to the branched, tree-like fronds of bluegrass and orchardgrass, and the elaborate tufts of brome. Some grasses create a thick, underlying carpet of roots and connecting runners called rhizomes, which protect the ground from water runoff and traffic damage; this makes them a preferred crop for pastures.

There are considerable advantages to growing grass and legume hays together as one crop. First, horses consider legumes tops in the palatability sweepstakes, so combining the two might encourage a horse which would turn up his nose at straight grass hay to accept and consume a mixed flake. 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--and more marketable for the farmer. Third, the addition of nitrogen-producing legumes to a grass hay crop actually helps fertilize the field and increase 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, depending on the climate, soil type, and demand.

Harvesting And Storing

Hay can be pressed into cubes, chopped and processed into pellets, or fermented as silage or "haylage" (more on these in a future issue!), but most often, it is cut and allowed to sun-cure until it has a moisture content of less than 20%, after which it is baled. Growers have to do a delicate dance with the weather, cutting hay when they hope there is the greatest likelihood of the crop's drying before it is rained on...and sometimes losing the gamble. The stage of growth of the hay limits the weather window considerably; in order to ensure good nutritional content, hay should be cut before it reaches the mid-bloom stage. Once seed-heads have formed, the plant puts its energy into propagation, and the stalk and leaves become tougher, more fibrous, and less palatable; the crude protein level of brome grass, for example, might drop from 12.6% at mid-bloom to 5.6% when fully mature. (Researchers have estimated that allowing hay plants to stand past the "boot" stage, when seed heads first appear, decreases crude protein levels by about one-quarter of a percent per day and digestible energy by nearly one-half of a percent per day.)

Moisture levels are crucial to quality hay. An ill-timed thunderstorm while hay is curing can reduce the leaf content in the resulting bales by up to 15%, destroy up to 34% of the non-structural carbohydrates and 25% of the protein yield, and decrease the overall yield of the crop by up to 40%. Baling while the moisture of the hay is still too high (greater than 20%, or 18% for large rectangular or round bales) increases the chance of mold growth, decreases the protein utilization, and makes the hay less palatable. In addition, hay that is baled wet tends to generate heat (both through the continued respiration of the hay, which can create an environment of 90-100% humidity in the bale, and the metabolic activity of microorganisms associated with the plant material--including heat-resistant fungi that become active at a temperature between 113-150° Fahrenheit). Once these processes are set in motion in baled hay, temperatures can continue to rise through a period of about four to 10 weeks (especially when stored in a warm loft with poor air circulation). At temperatures above 175° Fahrenheit, heat-producing chemical reactions serve to worsen the situation further. A subsequent rapid oxidation of reactive compounds in the hay can actually cause the temperature to rise to ignition point--between 448-527° Fahernheit. If enough oxygen is present, spontaneous combustion can result, not only destroying that hay, but putting horses and buildings at huge risk!

Not storing bales that feel or smell warm anywhere near a barn and regular checks with a thermometer (slipped down between bales in your stack) are excellent safety precautions. Hay that has a temperature of about 140° Fahrenheit should be removed from the barn--slowly, as even throwing or moving the hay quickly could be enough to cause it to burst into flames.

Although regular square bales of hay might vary in weight from about 40-100 lbs., any unusually heavy bales should be regarded as suspicious--they might have an excessively high moisture content. Those bales are better discarded.

Heating occurs, to some extent, in all forage materials that contain more than 15% moisture, and many farmers use spray-on drying agents (often containing potassium carbonate) to reduce the risk of baling too wet. The chemicals in the drying agents break down the waxy cuticle layer on the stem, which increases the rate of moisture loss and can cut curing time by 50-70%. They also make the leaves less brittle, which results in less leaf (and nutrient) loss.

Another approach is to use a hay preservative, such as propionic acid or sodium diacetate, which inhibits mold and can allow growers to bale hay at up to 25% moisture. The resulting hay tends to have higher yields, better color, a higher percentage of leaves, and less dust and mildew than conventionally baled hay--not a bad payoff for a chemical that costs about $5 per ton of hay. Both hay preservatives and drying agents have been demonstrated to be safe for use on hay for horses, and they have no demonstrated effect on palatability. Their only drawback is that some of the chemicals are corrosive to the growers' equipment. Growers producing large square or round bales often use these products as a precaution against spoilage even when curing conditions are ideal.

Even under the best conditions, hay suffers losses of about 30-70% during the harvesting and baling processes, with legumes taking a higher toll than the tougher grasses. Losses from normal respiration account for about 5-6% 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 shatter and 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.

In warmer regions of North America, growers sometimes can get as many as seven or eight cuttings from a hayfield, although in the northern states and Canada, two (or at most three) cuttings are the norm.

"First-cut" hay generally is high in nutritional value if harvested at the proper time. It runs the lowest risk of blister beetles (which usually appear after midsummer), but sometimes it contains large numbers of weeds that have grown up since the last cutting of the previous season. And because it is harvested early in the year, it might be more difficult to get it sun-cured without being rained on.

Later cuttings, in the heat of the summer, have lower nutritional value, because when temperatures are hot, the plants put their energy into rapid growth, with more stem and fewer leaves. But as the weather gets cooler in the fall, hay cuttings usually have a higher leaf and nutrient content, fewer weeds, and, in many areas, the best opportunity of being harvested without rain. Determining the quality of your hay should be based less on the "cut" from which it comes than from its stage of bloom when harvested.

Assessing Quality

Much of the assessment of the quality of your hay can be done the old-fashioned way--break open a bale and scratch 'n' sniff! Good-quality hay should be green, rather than yellow or brown (keep in mind that some hays, particularly some varieties of clover, might cure to quite a dark color, which is not necessarily an indicator of mold growth). The hay should have a high leaf content ("stemmy" hay is too mature), few weeds, and it 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 usually is an indicator that the grower had the tines on his harvester set too low. As a general rule, the nicer you feel that the loose hay would be to sleep in, the better the quality!

To really determine the nutrient content of the hay, however, you'll need to do a hay analysis. Appearance is a poor indicator of nutritive value--even grass hays that appear very similar might vary two-fold in protein content. Your state extension agent, university nutrition specialist, or local feed company should provide this service for a cost of about $20-$40. The results can be invaluable. Performing a hay analysis whenever you get a shipment of hay is an excellent management routine, especially since the results can have a significant impact on the grains and supplements you choose to feed.

Hay can be sampled either with a corer (which is inserted into several bales to draw samples), or, more simply, 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, acid detergent fiber (ADF, which is the indigestible portion), calcium, phosphorus, and the all-important moisture content. You also can request other data, such as the copper or selenium content of hay. Your feed specialist or extension agent also can help interpret the results and balance the rations in your barn to complement the nutrients in your hay.

How much to feed? As a rough guideline, horses should consume 1-2% of their body weight each day in forage products--at least 50% of their total diets under all but the most extreme exercise programs. 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. This can be done very simply by standing on a bathroom scale, with and without the flake of hay, and subtracting the difference.

When you are feeding hay, it's important to remember that, at heart, horses are grazing animals, programmed to chew on stemmy, fibrous plants for at least 12 hours a day. That urge to chew can be as compelling as a rodent's, so hay fulfills two functions in your barn--it provides nutrients (and keeps the digestive system in good health), and it keeps horses busy (and thus not chewing the wood fences, stall doors, or a neighbor's tail!). An almost constant supply of small amounts of hay is far more beneficial than one or two large feedings a day because it mimics the horse's natural grazing habits.

Make lots of good-quality hay the basis of your horses' diets, and you'll reap the benefits in terms of both health and contentment.

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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