Understanding Forages

  

Forage should be the basis of any equine diet.

Photo: Photos.com

We’ve said it before; we’ll say it again: Forage should be the basis of any equine diet. So understanding pasture, hay, and other fiber sources is an important part of your everyday management. So, too, is knowing which fiber sources are appropriate for your horse.
Forage can be loosely defined as any feed made up of the stems, leaves, and stalks of plants, and which has a minimum fiber content of 18% and a relatively low dietary energy (DE) content. The most natural, least expensive, and safest feed for horses, forage 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 stable vices derived from having too little to chew on.
Although horses have been known to nibble on tree leaves and branches, they’re primarily grazers, not browsers like deer, and grasses make up most of their natural diet. If you live in a temperate climate with no chance of drought, your horses might have the luxury of nutritious grazing—fresh forage—year-round. But for most North Americans, there’s a good portion of the year when good pasture is just not available, and hay—grasses and/or legumes that have been sun-cured, dried, and baled for convenient feeding—picks up the slack.
Hay, the most common type of forage fed to horses, averages 28% to 38% crude fiber and has a DE level of about 1.95 to 2.5 Mcal per kg. (Cereal grains, by contrast, contain between 2% and 12% crude fiber and have a much higher DE, averaging 3.3 to 3.7 Mcal/kg.) Hay is high in calcium (Ca) and low in phosphorus (P)—and 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) might contain 20% crude protein or even higher while grass hays (such as timothy, bermudagrass, or orchardgrass) average about 11% to 14% protein and can go as low as 4%. The protein content of hay is largely determined 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 might be inadequate to meet an adult horse’s nutrient requirements for maintenance.
Cereal grain hay, is rarely fed to horses in North America as it is not terribly 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; it makes good bedding but poor feed.)
Far more common are grass hays and legume hays. Of the legumes, alfalfa, also called lucerne, 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 legume hay includes clovers, birdsfoot trefoil, lespedeza, cowpeas, vetch, and even soybeans. Horses almost always prefer legume hays over grass hays, and this type contains 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, they’re the preferred hays for young, growing horses as well as lactating mares. But legumes are generally more costly, and in some parts of North America might 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’s an easy crop to establish on most soils, and tolerates cold well, beginning to grow actively early in the spring, weeks before most other hay crops. But timothy doesn’t cope well with extremes of heat and humidity, so in the central and southern United States, growers sometimes may turn to alternatives such as quick-curing coastal bermudagrass (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, 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, and ryegrass are some of the other varieties of grass hays fed to horses. Not only do grass hays not harbor blister beetles, but they often are less dusty than legume hays, making them a preferred choice for horses with respiratory problems. And 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 the way legume leaves do. Legume stalks are often 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 that would turn his nose up at straight grass hay to accept and consume a mixed flake. Second, a lower-protein grass hay might help “balance out” the high protein level of a legume and create bales that are appropriate to feed to mature horses—and more marketable for the farmer. And 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 North American, mixed hay is the preferred feed for horses—though the mix can be any of a number of combinations of legumes and grasses, depending on the climate, soil type, and demand.