Equine nutrition
Equine nutrition is the feeding of
Horses are non-
In practical terms, horses prefer to eat small amounts of food steadily throughout the day, as they do in nature when grazing on pasture lands.[2] 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
The digestive system
Horses and other members of the genus Equus are adapted by evolutionary biology to eating small amounts of the same kind of food all day long. In the wild, horses ate prairie grasses in semi-arid regions and traveled significant distances each day in order to obtain adequate nutrition.[9] Therefore, their digestive system was made to work best with a small but steady flow of food that does not change much from day to day.
Chewing and swallowing
Digestion begins in the
The esophagus carries food to the stomach. The esophagus enters the stomach at an acute angle, creating a one-way valve, with a powerful sphincter mechanism at the gastroesophageal junction, which is why horses cannot vomit.[3] The esophagus is also the area of the digestive tract where horses may suffer from choke. (see Illnesses related to improper feeding below)
The stomach and small intestine
Horses have a small stomach for their large size, which limits the amount of food that can be taken in at one time. The average sized horse has a stomach with a capacity of only 4 US gallons (15 L), and works best when it contains about 2 US gallons (7.6 L). One reason continuous foraging or several small feedings per day are better than one or two large meals is because the stomach begins to empty when it is two-thirds full, whether the food in the stomach is processed or not.[3]
The
The cecum and large intestine
The
The large
Nutrients
Like all animals, equines require five main classes of nutrients to survive:
Water
Water makes up between 62-68% of a horse's body weight and is essential for life.[14] Horses can only live a few days without water,[13] becoming dangerously dehydrated if they lose 8-10% of their natural body water.[14] Therefore, it is critically important for horses to have access to a fresh, clean, and adequate supply of water.
An average 1,000-pound (450 kg) horse drinks 10 to 12 US gallons (38–45 L) of water per day, more in hot weather, when eating dry forage such as
Water plays an important part in digestion. The forages and grains horses eat are mixed with saliva in the mouth to make a moist bolus that can be easily swallowed. Therefore, horses produce up to 10 US gallons (38 L) or 85 lb. of saliva per day.[10]
Energy nutrients and protein
Nutritional sources of energy are
Fat exists in low levels in plants and can be added to increase the energy density of the diet. Fat has 9 megacalories (38 MJ) per kilogram of energy,[1] which is 2.25 times that of any carbohydrate source.[19] Because equids have no gall bladder to store large quantities of bile, which flows continuously from the liver directly into the small intestine, fat, though a necessary nutrient, is difficult for them to digest and utilize in large quantities.[20] However, they are able to digest a greater amount of fat than can cattle.[18] Horses benefit from up to 8% fat in their diets, but more does not always provide a visible benefit. Horses can only have 15-20% fat in their diet without the risk of developing diarrhea.[19]
Soluble carbohydrates are found in nearly every feed source;
Vitamins and minerals
Horses that are not subjected to hard work or extreme conditions usually have more than adequate amounts of vitamins in their diet if they are receiving fresh, green, leafy forages. Sometimes a vitamin/mineral supplement is needed when feeding low-quality hay, if a horse is under stress (illness, traveling, showing, racing, and so on), or not eating well. Grain has a different balance of nutrients than forage, and so requires specialized supplementation to prevent an imbalance of vitamins and minerals.[1]
Minerals are required for maintenance and function of the
Calcium and phosphorus are needed in a specific ratio of between 1:1 and 2:1. Adult horses can tolerate up to a 5:1 ratio, foals no more than 3:1. A total ration with a higher ratio of phosphorus than calcium is to be avoided.[22] Over time, imbalance will ultimately lead to a number of possible bone-related problems such as osteoporosis.[26]
Foals and young growing horses through their first three to four years have special nutritional needs and require feeds that are balanced with a proper calcium:phosphorus ratio and other trace minerals. A number of skeletal problems may occur in young animals with an unbalanced diet.[22] Hard work increases the need for minerals; sweating depletes sodium, potassium, and chloride from the horse's system. Therefore, supplementation with electrolytes may be required for horses in intense training, especially in hot weather.[1]
Types of feed
Equids can consume approximately 2–2.5% of their body weight in dry feed each day. Therefore, a 1,000 lb (450 kg) adult horse could eat up to 25 lb (11 kg) of food.[27] Foals less than six months of age eat 2-4% of their weight each day.[28]
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.[28] 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.[27]
Forages
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.[7]
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.
Haylage, also known as Round bale silage is a term for grass sealed in airtight plastic bags, a form of forage that is frequently fed in the United Kingdom and continental Europe, but is not often seen in the United States.[30] Because haylage is a type of silage, hay stored in this fashion must remain completely sealed in plastic, as any holes or tears can stop the preservation properties of fermentation and lead to mold or spoilage. Rodents chewing through the plastic can also spoil the hay introducing contamination to the bale.[8] If a rodent dies inside the plastic, the subsequent botulism toxins released can contaminate the entire bale.
Sometimes, straw or chaff is fed to animals. However, this is roughage with little nutritional value other than providing fiber.[31] 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.[31][32] Straw is more often used as a bedding in stalls to absorb wastes.
Concentrates
Grains
Whole or crushed
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 than other grains.[7][21]
Corn (USA), or maize (British English), 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, it is easy to over-feed, causing obesity, so horses are seldom fed corn all by itself. Nutritionists caution that moldy corn is poisonous if fed to horses.[13]
Barley is also fed to horses, but needs to be processed to crack the seed hull and allow easier digestibility.[7] It is frequently fed in combination with oats and corn, a mix informally referred to by the acronym "COB" (for Corn, Oats and Barley).
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.[21] Some of these prepared feeds are manufactured in pelleted form, others retain the grains in their original form. In many cases molasses is used as a binder to keep down dust and for increased palatability.[7] Grain mixes with added molasses are usually called "sweet feed" in the United States 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.[34]
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.[27] Extra fat and protein are sometimes added to the horse's diet, along with vitamin and mineral supplements.[19] 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
Most horses only need quality forage, water, and a salt or mineral block.
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.[35] In addition, genetic factors play a role. Some animals are naturally easy keepers (good doers), which means that they can thrive on small amounts of food and are prone to obesity and other health problems if overfed. Others are hard keepers (poor doers), meaning that they are prone to be thin and require considerably more food to maintain a healthy weight.
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[5] (along with water and supplemental salt), and any feed ration should be at least 50% forage.[28] 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 lb (0.91 kg) to 5 lb (2.3 kg) 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.[18] It is available in both pelleted and shredded form, pellets must be soaked significantly longer than shredded beet pulp.
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 lb (45 kg) of horse, in order to keep the digestive system functioning properly and to meet the horse's urge to graze.[34]
When horses graze under natural conditions, they may spend up to 18 hours per day doing so.[36] However, on modern irrigated pastures, they may have their nutritional needs for forage met in as little as three hours per day, depending on the quality of grass available.
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.[37]
Feeding concentrates
Concentrates, when fed, are recommended to be provided in quantities no greater than 1% of a horse's body weight per day,
In general, the portion of the ration that should be grain or other concentrated feed is 0-10% grain for mature idle horses; between 20-70% for horses at work, depending on age, intensity of activity, and energy requirements.
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.[41] 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.[15][18]
Even a slightly dehydrated horse is at higher risk of developing impaction
Special feeding issues for ponies
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.[42] Ponies easily become obese from overfeeding and are at high risk for colic and, especially, laminitis.[43] Fresh grass is a particular danger to ponies; they can develop laminitis in as little as one hour of grazing on lush pasture.[44]
Incorrect feeding is also as much a concern as simple overfeeding. Ponies and miniatures need a diet relatively low in sugars and starches and calories, but higher in fibers. Miniature horses in particular need fewer calories pound for pound than a regular horse, and are more prone to
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 lb (0.45 kg) of forage for every 100 lb (45 kg).[42] 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.[30] 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.[42] In the UK, extruded pellets designed for ponies are sometimes called "pony nuts".[30]
Special feeding issues for mules and donkeys
Like 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.[45] If mules are fed concentrates, they only need about half of what a horse requires.[46] Like horses, mules require fresh, clean water, but are less likely to over-drink when hot.[45]
Donkeys, like mules, need less protein and more fiber than horses. Although the donkey's gastrointestinal tract has no marked differences in structure to that of the horse, donkeys are more efficient at digesting food and thrive on less forage than a similar sized pony.[47] They only need to eat 1.5% of their body weight per day in dry matter.[48] It is not fully understood why donkeys are such efficient digestors, but it is thought that they may have a different microbial population in the large intestine than do horses, or possibly an increased gut retention time.[49]
Donkeys 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.[50] Like ponies and mules, in a lush climate, donkeys are prone to obesity and are at risk of laminitis.[51]
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.[52]
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.[18]
Feed storage
All hay and concentrated feeds must be kept dry and free of
It is generally not safe to give a horse feed that was contaminated by the remains of a dead animal. This is a potential source of botulism.[53] 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.
Dental issues
Horses'
Colic, choke, and laminitis can be life-threatening when a horse is severely affected, and veterinary care is necessary to properly treat these conditions.[56] Other conditions, while not life-threatening, may have serious implications for the long-term health and soundness of a horse.
Colic
Horse colic itself is not a disease, but rather a description of symptoms connected to abdominal pain.[3] It can occur due to any number of digestive upsets, from mild bloating due to excess intestinal gas to life-threatening impactions.[57] Colic is most often caused by a change in diet, either a planned change that takes place too quickly, or an accidental change, such as a horse getting out of its barn or paddock and ingesting unfamiliar plants. But colic has many other possible triggers including insufficient water, an irregular feeding schedule, stress, and illness.[58] Because the horse cannot vomit and has a limited capacity to detoxify harmful substances, anything upsetting to the horse must travel all the way through the digestive system to be expelled.
Choke
Choke is not as common as colic, but is nonetheless commonly considered a veterinary emergency. The most common cause of choke is horses not chewing their food thoroughly, usually because of eating their food too quickly, especially if they do not have sufficient access to water, but also sometimes due to dental problems that make chewing painful. It is exceedingly difficult for a horse to expel anything from the esophagus, and immediate treatment is often required. Unlike choking in humans, choke in horses does not cut off respiration.[3][59]
Laminitis
Horses are also susceptible to laminitis, a disease of the lamina of the hoof. Laminitis has many causes, but the most common is related to a sugar and starch overload from a horse overeating certain types of food, particularly too much pasture grass high in fructan in early spring and late fall, or by consuming excessive quantities of grain.[60]
Growth disorders
Young horses that are overfed or are fed a diet with an improper calcium:phosphorus ratio over time may develop a number of growth and
Heaves
Moldy or dusty hay fed to horses is the most common cause of
"Tying up"
Equine exertional rhabdomyolysis, also known as "tying up" or azoturia, is a condition to which only some horses are susceptible and most cases are linked to a genetic mutation.[66] In horses prone to the condition, it usually occurs when a day of rest on full grain ration is followed by work the next day. This pattern of clinical signs led to the archaic nickname "Monday morning sickness". The condition may also be related to electrolyte imbalance. Proper diet management may help minimize the risk of an attack.[67][68]
See also
- Easy keeper (US) Good doer (UK)
- Fodder
- Forage
- Geriatric horses
- Grain
- Hard keeper (US) Poor doer (UK)
- Hay
- Henneke horse body condition scoring system
- Horse body mass
- Horse tongue
- Horse care
- List of plants poisonous to equines
Footnotes and other references
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- ^ "Horse Nutrition - Frequency." Bulletin 762-00, Ohio State University. Web site accessed February 9, 2007.
- ^ ISBN 0-87605-606-0
- ^ "Colic in Horses" ASC-128, Cooperative Extension Service, University of Kentucky, College of Agriculture, Equine Section, Department of Animal Sciences. web site accessed March 14, 2007
- ^ a b c d e March, Linda. "Feeding Your Horse To Avoid Problems," from University of Illinois, College of Veterinary Medicine. Archived 2007-02-02 at the Wayback Machine Web site accessed February 16, 2007
- ^ a b A. Cirelli, Jr. and B. Cloud. "Suburban Horse Keeping." (PDF) Fact Sheet: 94-09, Cooperative Extension Service, University of Nevada, Reno. Web site accessed July 4, 2009.
- ^ a b c d e f g h "Horse Nutrition - Carbohydrates and fats." Bulletin 762-00, Ohio State University. Web site accessed February 9, 2007.
- ^ a b Karen Spivey and Jackie Nix. "Haylage" North Carolina Cooperative Extension Service. Web site accessed July 4, 2009.
- ISBN 0-684-82768-9
- ^ a b c d e f g "Horse Nutrition - The Horse's Digestive System." Bulletin 762-00, Ohio State University. Web site accessed February 9, 2007.
- ^ "Digestive Aids: Does Your Horse Need Them?." Archived 2008-05-21 at the Wayback Machine Equine Review Accessed July 4, 2009.
- ^ a b "Colic in Horses | Animal & Food Sciences". afs.ca.uky.edu. Retrieved 2021-02-18.
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- ^ a b "Horse Nutrition - Diet Factors - Water." Bulletin 762-00, Ohio State University. Web site accessed February 9, 2007.
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- ^ Gastric Ulcers in the Adult Horse
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