- Equine Nutrition -

Equine nutrition refers to the feeding of horses, ponies, mules, donkeys, and other equines. Correct and balanced nutrition is a critical component of proper horse care. Horses are herbivores, a type of non-ruminant known as a "hind-gut fermentor." What this means is that horses have only one stomach, similar to humans. However, unlike humans, they also have to digest plant fiber that comes from grass and hay. Therefore, unlike ruminants, who digest fiber in plant matter by use of a multichambered stomach, horses use bacterial fermentation that occurs in the organ known as the cecum (or caecum) to break down cellulose.

In practical terms, horses prefer to eat small amounts of food steadily throughout the day, as they do in nature when grazing on pasture. Although this is not always possible with modern stabling practices and human schedules that favor feeding horses twice a day, it is important to remember the underlying biology of the animal when determining what to feed, how often, and in what quantities. The digestive system of the horse is somewhat delicate. Because horses are unable to regurgitate food, except from the esophagus, if they overeat or eat something poisonous, vomiting is not an option. They also have a long, complex large intestine and a balance of beneficial bacteria in their cecum that can be upset by rapid changes in feed. Because of these factors, they are very susceptible to colic, which is a leading cause of death in horses. Therefore, horses require clean, high-quality feed, provided at regular intervals, and may become ill if subjected to abrupt changes in their diets.

Horses are also sensitive to molds and toxins. For this reason, they must never be fed contaminated fermentable materials such as lawn clippings. Fermented silage, sometimes called "haylage" is fed to horses in some places; however, contamination or failure of the fermentation process that allows any mold or spoilage may be toxic.

Horses can consume approximately 2% to 2.5% of their body weight in dry feed each day. Therefore, a 1000 lb adult horse could eat up to 25 pounds of food. Foals less than six months of age eat 2 to 4% of their weight each day. Solid feeds are placed into three categories: forages (such as hay and grass), concentrates (including grain or pelleted rations), and supplements (such as prepared vitamin or mineral pellets). Equine nutritionists recommend that 50% or more of the animal's diet by weight should be forages. If a horse is working hard and requires more energy, the use of grain is increased and the percentage of forage decreased so that the horse obtains the energy content it needs for the work it is performing. However, forage amount should never go below 1% of the horse's body weight per day.

Forages
Good quality grass hay is green and has visible leaves and young seed heads. Forages, also known as "roughage," are plant materials classified as legumes or grasses, found in pastures or in hay. Often, pastures and hayfields will contain a bland of both grasses and legumes. Nutrients available in forage vary greatly with maturity of the grasses, fertilization, management, and environmental conditions. Grasses are tolerant of a wide range of conditions and contain most necessary nutrients. Some commonly used grasses include timothy, brome, fescue, coastal bermuda, orchard grass, and Kentucky bluegrass.

Legumes such as clover or alfalfa are usually higher in protein, calcium, and energy than grasses. However, they require warm weather and good soil to produce the best nutrients. Legume hays are generally higher in protein than the grass hays. They are also higher in minerals, particularly calcium, but have an incorrect ratio of calcium to phosphorus. Because they are high in protein, they are very desirable for growing horses or those subjected to very hard work, but the calcium:phosphorus ratio must be balanced by other feeds to prevent bone abnormalities.

Hay is a dried mixture of grasses and legumes. It cut in the field and then dried and baled for storage. Hay is most nutritious when it is cut early on, before the seed heads are fully mature and before the stems of the plants become tough and thick. Hay that is very green can be a good indicator of the amount of nutrients in the hay; however, color should not be used as sole indicator - smell and texture are also important. Hay can be analyzed by many laboratories and that is the most reliable way to tell the nutritional values it contains. Moldy or dusty hay should not be fed to horses, as it is the most common cause of Recurrent airway obstruction, also known as COPD or "heaves."

Hay, particularly alfalfa, is sometimes compressed into pellets or cubes. Processed hay can be of more consistent quality and is more convenient to ship and to store. It is also easily obtained in areas that may be suffering localized hay shortages. However, these more concentrated forms can be overfed and horses are somewhat more prone to choke on them. On the other hand, hay pellets and cubes can be soaked until they break apart into a pulp or thick slurry, and in this state are a very useful source of food for horses with tooth problems such as dental disease, tooth loss due to age, or structural anomalies.

Another type of forage sometimes provided to horses is beet pulp, a byproduct left over from the processing of sugar beets, which is high in energy as well as fiber. Sometimes, straw or chaff from cereal grains is fed to animals. However, this is roughage with little nutritional value. It is not recommended by nutritionists as a horse feed, though it is sometimes used as a filler; it can slow down horses who eat their grain too fast, or it can provide additional fiber when the horse must meet most nutritional needs via concentrated feeds. Straw is more often used as a bedding in stalls to absorb wastes.

Concentrates
Oats - A premixed ration of crimped corn, oats, barley and pelleted supplement
Grains - Whole or crushed grains are the most common form of concentrated feed, sometimes referred to generically as "oats" or "corn" even if those grains are not present, also sometimes called "straights" in the UK.
Oats are the most popular grain for horses. Oats have a lower digestible energy value and higher fiber content than most other grains. They form a loose mass in the stomach that is well suited to the equine digestive system. They are also more palatable and digestible other grains.

Corn, referred to as Maize in the UK, is the second most palatable grain. It provides twice as much digestible energy as an equal volume of oats and is low in fiber. Because of these characteristics, is easy to over-feed corn, causing obesity, so horses are seldom fed corn all by itself. Nutritionists caution horse owners that moldy corn should never be fed because it is poisonous to horses. Barley is also fed to horses, but needs to be processed to crack the seed hull and allow easier digestibility. It is frequently fed in combination with oats and corn, a mix informally referred to by the acronym "COB" (for Corn, Oats and Barley).

Wheat is generally not used as a concentrate. However, wheat bran is sometimes added to the diet of a horse for supplemental nutrition, usually moistened and in the form of a bran mash. Wheat bran is high in phosphorus, so must be fed carefully so that it does not cause an imbalance in the Ca:P ratio of a ration. Once touted for a laxative effect, this use of bran is now considered unnecessary, as horses, unlike humans, obtain sufficient fiber in their diets from other sources.

Mixes and Pellets
Many feed manufacturers combine various grains and add additional vitamin and mineral supplements to create a complete premixed feed that is easy for owners to feed and of predictable nutritional quality. Some of these prepared feeds are manufactured in pelleted form, others retain the grains in their original form. In many cases molasses as a binder to keep down dust and for increased palatability.Grain mixes with added molasses are usually called "Sweet feed" in the USA and "Coarse mix" in the United Kingdom. Pelleted or extruded feeds (sometimes referred to as "nuts" in the UK) may be easier to chew and result in less wasted feed. Horses generally eat pellets as easily as grain. However, pellets are also more expensive, and even "complete" rations do not eliminate the necessity for forage.

Supplements
The average modern horse on good hay or pasture with light work usually does not need supplements; however, horses subjected to stress due to age, intensive athletic work, or reproduction may need additional nutrition.  Extra fat and protein are sometimes added to the horse's diet, along with vitamin and mineral supplements. Soybean meal is a common protein supplement, and averages about 44% crude protein. The protein in soybean meal is high-quality, with the proper ratio of dietary essential amino acids for equids. Cottonseed meal, Linseed meal, and peanut meal are also used, but are not as common.

Vegetable oil is a common fat source added to a ration. Corn oil is particularly popular, but other oils are used as well. Rice bran is a very good fat supplement that contains 20% fat as well as fiber and other nutrients.  Flax seed is another good source of fat, though it must ground up for horses to digest it. Some commercial feed manufacturers now make products containing both flaxseed and rice bran. There are hundreds, if not thousands of commercially prepared vitamin and mineral supplements on the market, many tailored to horses with specialized needs.

Feeding practices
A pelleted or extruded horse ration contains grain and other plant products, plus vitamin and mineral supplements.Most horses only need quality forage, water and a salt or mineral block. Grain or other concentrates are often not necessary. But, when grain or other concentrates are fed, quantities must be carefully monitored. To do so, horse feed is measured by weight, not volume. For example, 1 lb. of oats has a different volume than 1 lb. of corn. When continuous access to feed is not possible, it is more consistent with natural feeding behavior to provide three small feedings per day instead of one or two large ones. However, even two daily feedings is preferable to only one. To gauge the amount to feed, a weight tape, available at most feed stores, can be used to provide a reasonably accurate estimate of a horse's weight. The tape measures the circumference of the horse's barrel, just behind the withers and elbows, and the tape is calibrated to convert inches or centimeters into approximate pounds or kilograms.

Actual amounts fed vary by the size of the horse, the age of the horse, the climate, and the work to which the animal is put. In addition, genetic factors play a role. Some animals are naturally easy keepers, which means that they can thrive on relatively small amounts of food and are prone to obesity and other health problems if overfed. Others are hard keepers, meaning that they are prone to be thin and require considerably more food to maintain a healthy weight. Veterinarians are usually a good source for recommendations on appropriate types and amounts of feed for a specific horse. There are also numerous books written on the topic. Feed manufacturers usually offer very specific guidelines for how to select and properly feed products from their company, and in the United States, the local office of the Cooperative Extension Service can provide educational materials and expert recommendations.

Feeding forages
Equids always require forage. When possible, nutritionists recommend it be available at all times, at least when doing so does not overfeed the animal and lead to obesity. It is safe to feed a ration that is 100% forage (along with water and supplemental salt), and any feed ration should be at least 50% forage. Hay with alfalfa or other legumes has more concentrated nutrition and so is fed in smaller amounts than grass hay, though many hays have a mixture of both types of plant. When beet pulp is fed, a ration of 2 to 5 pounds is usually soaked in water for 3 to 4 hours prior to feeding in order to make it more palatable, and to minimize the risk of choke and other problems. It is usually soaked in a proportion of one part beet pulp to two parts water. Beet pulp is usually fed in addition to hay, but occasionally is a replacement for hay when fed to very old horses who can no longer chew properly.

Some pelleted rations are designed to be a "complete" feed that contains both hay and grain, meeting all the horse's nutritional needs. However, even these rations should have some hay or pasture provided, a minimum of a half-pound of forage for every 100 pounds of horse, in order to keep the digestive system functioning properly and to meet the horse's urge to graze. Recent studies address the level of various non-structural carbohydrates (NSC), such as fructan, in forages. Too high an NSC level causes difficulties for animals prone to laminitis or equine polysaccharide storage myopathy (EPSM). NSC cannot be determined by looking at forage, but hay and pasture grasses can be tested for NSC levels.

Feeding concentrates
Concentrates, when fed, are recommended to be provided in quantities no greater than 1% of a horse's body weight per day, and preferably in two or more feedings. If a ration needs to contain a higher percent of concentrates, such as that of a race horse, bulky grains such as oats should be used as much as possible; a loose mass of feed helps prevent impaction colic. Peptic ulcers are linked to a too-high concentration of grain in the diet, particularly noticed modern racehorses, where some studies show such ulcers affecting up to 90% of all race horses.

In general, the portion of the ration that should be grain or other concentrated feed is 0 to 10% grain for mature idle horses; between 20 to 70% for horses at work, depending on age, intensity of activity and energy requirements. Concentrates should not be fed to horses within one hour before or after a heavy workout. Concentrates also need to be adjusted to level of performance. Not only can excess grain and inadequate exercise lead to behavior problems, it may also trigger Equine Exertional Rhabdomyolysis, or "tying up," in horses prone to the condition.

Access to water
Horses normally require free access to all the fresh, clean water they want, and to avoid dehydration, should not be kept from water longer than four hours at any one time. However, water may need to be temporarily limited in quantity when a horse is very hot after a heavy workout. As long as a hot horse continues to work, it can drink its fill at periodic intervals, provided that common sense is used and that an overheated horse is not forced to drink from extremely cold water sources. But when the workout is over, a horse needs to be cooled out and walked for 30—90 minutes before it can be allowed all the water it wants at one time. However, dehydration is also a concern, so some water needs to be offered during the cooling off process. A hot horse will properly rehydrate while cooling off if offered a few swallows of water every three to five minutes while being walked. Sometimes the thirst mechanism does not immediately kick in following a heavy workout, which is another reason to offer periodic refills of water throughout the cooling down period.

Even a slightly dehydrated horse is at higher risk of developing impaction colic. Additionally, dehydration can lead to weight loss because the horse cannot produce adequate amounts of saliva, thus decreasing the amount of feed and dry forage consumed. Thus, it is especially important for horse owners to encourage their horses to drink when there is a risk of dehydration; when horses are losing a great deal of water in hot weather due to strenuous work, or in cold weather due to horses' natural tendency to drink less when in a cold environment. To encourage drinking, owners may add electrolytes to the feed, additives to make the water especially palatable (such as apple juice), or, when it is cold, to warm the water so that it is not at a near-freezing temperature.

Special feeding issues for Ponies
Ponies need less feed than full-sized horses. Ponies and miniature horses are usually easy keepers and need less feed than full-sized horses. This is not only because they are smaller, but also, because they evolved under harsher living conditions than horses, they use feed more efficiently. Ponies easily become obese from overfeeding and therefore are at high risk for colic, Equine Metabolic Syndrome, and, especially, laminitis. Fresh grass is a particular danger to ponies; they can develop laminitis in as little as one hour of grazing on lush pasture.

It is important to track the weight of a pony carefully, by use of a weight tape. Forages may be fed based on weight, at a rate of about 1 pound of forage for every 100 pounds. Forage, along with water and a salt and mineral block, is all most ponies require. If a hard-working pony needs concentrates, a ratio of no more than 30% concentrates to 70% forage is recommended. Concentrates designed for horses, with added vitamins and minerals, will often provide insufficient nutrients at the small serving sizes needed for ponies. Therefore, if a pony requires concentrates, feed and supplements designed specially for ponies should be used. In the UK, extruded pellets designed for ponies are sometimes called "pony nuts."

Special feeding issues for mules and donkeys
Donkeys and mules need less concentrated feed than horsesLike ponies, mules and donkeys are also very hardy and generally need less concentrated feed than horses. Mules need less protein than horses and do best on grass hay with a vitamin and mineral supplement. If mules are fed concentrates, they only need about half of what a horse requires. Like horses, mules require fresh, clean water, but are less likely to over-drink when hot.

Donkeys, like mules, need less protein and more fiber than horses. They do best when allowed to consume small amounts of food over long periods, as is natural for them in an arid climate. They can meet their nutritional needs on 6 to 7 hours of grazing per day on average dryland pasture that is not stressed by drought. If they are worked long hours or do not have access to pasture, they require hay or a similar dried forage, with no more than a 1:4 ratio of legumes to grass. They also require salt and mineral supplements, and access to clean, fresh water. Like ponies and mules, in a lush climate, donkeys are prone to obesity and are at risk of laminitis.

Treats
Many people like to feed horses special treats such as carrots, sugar cubes, peppermint candies or specially manufactured horse "cookies." Horses do not need treats, and due to the risk of colic or choke, many horse owners do not allow their horses to be given treats. There are also behavioral issues that some horses may develop if given too many treats, particularly a tendency to bite if hand-fed, and for this reason many horse trainers and riding instructors discourage the practice.

However, if treats are allowed, carrots and compressed hay pellets are common, nutritious, and generally not harmful. Apples are also acceptable, though it is best if they are first cut into slices. Horse "cookies" are often specially manufactured out of ordinary grains and some added molasses. They generally will not cause nutritional problems when fed in small quantities. However, many types of human foods are potentially dangerous to a horse and should not be fed. This includes bread products, meat products, candy, and carbonated or alcoholic beverages.

It was once a common practice to give horses a weekly bran mash of wheat bran mixed with warm water and other ingredients. It is still done regularly in some places. While a warm, soft meal is a treat many horses enjoy, and was once considered helpful for its laxative effect, it is not nutritionally necessary. An old horse with poor teeth may benefit from food softened in water, a mash may help provide extra hydration, and a warm meal may be comforting in cold weather, but horses have far more fiber in their regular diet than do humans, and so any assistance from bran is unnecessary. There is also a risk that too much wheat bran may provide excessive phosphorus, unbalancing the diet, and a feed of unusual contents fed only once a week could trigger a bout of colic.

Feed storage
All hay and concentrated feeds must kept dry and free of mold, rodent feces and other types of contamination that may cause illness in horses. Feed kept outside or otherwise exposed to moisture can develop mold quite quickly. Due to fire hazards, hay is often stored under an open shed or under a tarp, rather than inside a horse barn itself, but should be kept under some kind of cover. Concentrates take up less storage space, are less of a fire hazard, and are usually kept in a barn or enclosed shed. A secure door or latched gate between the animals and any feed storage area is critical. Horses accidentally getting into stored feed and eating too much at one time is a common but preventable way that horses develop colic or laminitis.

It is also important to never give a horse feed that was contaminated by the remains of a dead animal, it is a potential source of botulism. This is not an uncommon situation. For example, mice and birds can get into poorly stored grain and be trapped; hay bales sometimes accidentally contain snakes, mice, or other small animals that were caught in the baling machinery during the harvesting process.

Feeding behavior
Horses can become anxious or stressed if there are long periods of time between meals. They also do best when they are fed on a regular schedule, they are creatures of habit and easily upset by changes in routine. When horses are in a herd, their behavior is hierarchical; the higher-ranked animals in the herd eat and drink first. Low-status animals, who eat last, may not get enough food, and if there is little available feed, higher-ranking horses may keep lower-ranking ones from eating at all. Therefore, unless a herd is on pasture that meets the nutritional needs of all individuals, it is important to either feed horses separately, or spread feed out in separate areas to be sure all animals get roughly equal amounts of food to eat. In some situations where horses are kept together, they may still be placed into separate herds, depending on nutritional needs; overweight horses are kept separate from thin horses so that rations may be adjusted accordingly.

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