text: equine nutrition equine nutrition is the feeding of horses , ponies , mules , donkeys , and other equines . correct and balanced nutrition is a critical component of proper horse care . horses are non - ruminant herbivores of a type known as a " hindgut fermenter . " horses have only one stomach , as do humans . however , unlike humans , they also have to utilize plant fiber ( largely cellulose ) that comes from grass and hay . ruminants like cattle are foregut fermenters , and digest fiber in plant matter by use of a multi - chambered stomach , whereas horses use microbial fermentation in a part of the digestive system known as the cecum ( or caecum ) to break down the 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 . horses are unable to regurgitate food , except from the esophagus . thus , 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 microbes 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 or " " is fed to horses in some places ; however , contamination or failure of the fermentation process that allows any mold or spoilage may be toxic . 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 . 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 mouth . first , the animal selects pieces of forage and picks up finer foods , such as grain , with sensitive , prehensile , lips . the front teeth of the horse , called incisors , nip off forage , and food is ground up for swallowing by the premolars and molars . 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 . 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 size , which limits the amount of feed 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 . the small intestine is 50 to 70 feet ( 15 to 21 m ) long and holds 10 us gallons ( 38 l ) to 12 us gallons ( 45 l ) . this is the major digestive organ where 50 to 70 percent of all nutrients are absorbed into the bloodstream . bile from the liver acts here , combined with enzymes from the pancreas and small intestine itself . equids do not have a gall bladder , so bile flows constantly , an adaptation to a slow but steady supply of food , and another reason for providing fodder to horses in several small feedings . the cecum and large intestine the cecum is the first section of the large intestine . it is also known as the " water gut " or " hind gut . " it is a blind - ended pouch , about 4 feet ( 1 . 2 m ) long that holds 7 us gallons ( 26 l ) to 8 us gallons ( 30 l ) . the small intestine opens into the cecum , and the cellulose plant fiber in the food is fermented by microbes for approximately seven hours . the fermented material leaves the cecum through another orifice and passes to the large colon . the microbes in the cecum produce vitamin k , b - complex vitamins , proteins , and fatty acids . the reason horses must have their diets changed slowly is so the microbes in the cecum are able to modify and adapt to the different chemical structure of new feedstuffs . too abrupt a change in diet can cause colic , because new materials are not properly digested . the large colon , small colon , and rectum make up the remainder of the large intestine . the large colon is 10 to 12 feet ( 3 . 0 to 3 . 7 m ) long and holds up to 20 us gallons ( 76 l ) of semi - liquid matter . its main purpose is to absorb carbohydrates which were broken down from cellulose in the cecum . due to its many twists and turns , it is a common place for a type of horse colic called an impaction . the small colon is also 10 to 12 feet ( 3 . 0 to 3 . 7 m ) long , holds about 5 us gallons ( 19 l ) , is the area where the majority of water is absorbed , and where fecal balls are formed . the rectum is about one foot long , and acts as a holding chamber for waste , which is then expelled from the body via the anus . nutrients like all animals , equines require five main classes of nutrients to survive : water , energy ( primarily in the form of fats and carbohydrates ) , proteins , vitamins , and minerals . water water makes up between 62 - 68 % of a horse 's body weight and is essential for life . horses can only live a few days without water , becoming dangerously dehydrated if they lose 8 - 10 % of their natural body water . therefore , it is critically important for horses to have access to a fresh , clean , and adequate supply of water . an average 1 , 000 lb ( 450 kg ) horse drinks 10 us gallons ( 38 l ) to 12 us gallons ( 45 l ) of water per day , more in hot weather , when eating dry forage such as hay , or when consuming high levels of salt , potassium , and magnesium . horses drink less water in cool weather or when on lush pasture , which has a higher water content . when under hard work , or if a mare is lactating , water requirements may be as much as four times greater than normal . though they need a great deal of water , horses spend very little time drinking ; usually 1 – 8 minutes a day , spread out in 2 - 8 episodes . 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 . energy nutrients and protein nutritional sources of energy are fat and carbohydrates . protein is a critical building block for muscles and other tissues . horses that are heavily exercised , growing , pregnant or lactating need increased energy and protein in their diet . however , if a horse has too much energy in its diet and not enough exercise , it can become too high - spirited and difficult to handle . fat exists in low levels in plants and can be added to increase the energy density of the diet . fat has 9 ( 38 mj ) per kilogram of energy , which is 2 . 25 times that of any carbohydrate source . 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 . however , they are able to digest a greater amount of fat than can cattle . 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 . carbohydrates , the main energy source in most rations , are usually fed in the form of hay , grass , and grain . soluble carbohydrates such as starches and sugars are readily broken down to glucose in the small intestine and absorbed . insoluble carbohydrates , such as fiber ( cellulose ) , are not digested by the horse 's own enzymes , but are fermented by microbes in the cecum and large colon to break down and release their energy sources , volatile fatty acids . soluble carbohydrates are found in nearly every feed source ; corn has the highest amount , then barley and oats . forages normally have only 6 - 8 % soluble carbohydrate , but under certain conditions can have up to 30 % . sudden ingestion of large amounts of starch or high sugar feeds can cause at the least an indigestion colic , and at the worst potentially fatal colitis or laminitis . protein is used in all parts of the body , especially muscle , blood , hormones , hooves , and hair cells . the main building blocks of protein are amino acids . alfalfa and other legumes in hay are good sources of protein that can be easily added to the diet . most adult horses only require 8 - 10 % protein in their diet ; however , higher protein is important for lactating mares and young growing foals . 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 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 . minerals are required for maintenance and function of the skeleton , nerves , and muscles . these include calcium , phosphorus , sodium , potassium , and chloride , and are commonly found in most good - quality feeds . horses also need trace minerals such as magnesium , selenium , copper , zinc , and iodine . normally , if adult animals at maintenance levels are consuming fresh hay or are on pasture , they will receive adequate amounts of minerals in their diet , with the exception of sodium chloride ( salt ) , which needs to be provided , preferably free choice . some pastures are deficient in certain trace minerals , including selenium , zinc , and copper , and in such situations , health problems , including deficiency diseases , may occur if horses ' trace mineral intake is not properly supplemented . 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 . over time , imbalance will ultimately lead to a number of possible bone - related problems such as osteoporosis . 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 . 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 . 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 . foals less than six months of age eat 2 - 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 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 blend 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 . 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 . 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 . 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 is 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 is not the sole indicator of quality — 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 . 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 . , 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 . because 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 . 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 . 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 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 than other grains . 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 corn , causing obesity , so horses are seldom fed corn all by itself . caution horse owners that moldy corn is poisonous if fed 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 many feed manufacturers combine various grains and add additional vitamin and mineral supplements to create a complete 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 is used as a binder to keep down dust and for increased palatability . grain mixes with added molasses are usually called " sweet feed " in the united states and " coarse mix " in the united kingdom . 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 . there are hundreds , if not thousands of commercially prepared vitamin and mineral supplements on the market , many tailored to horses with specialized needs . 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 . meal , linseed meal , and peanut meal are also used , but are not as common . feeding practices 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 ( 0 . 45 kg ) of oats has a different volume than 1 lb ( 0 . 45 kg ) 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 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 circumference into approximate weight . 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 ( 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 . veterinarians are usually a good source for recommendations on appropriate types and amounts of feed for a specific horse . animal nutritionists are also trained in how to develop equine rations and make recommendations . 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 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 . 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 . when horses graze under natural conditions , they may spend up to 18 hours per day doing so . 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 ( ) . 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 . ulcers are linked to a too - high concentration of grain in the diet , particularly noticed in 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 - 10 % grain for mature idle horses ; between 20 - 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 serious health problems that include equine rhabdomyolysis , or " tying up , " in horses prone to the condition . another possible risk are various forms of horse colic . a relatively uncommon , but usually fatal concern is colitis - x , which may be triggered by excess protein and lack of forage in the diet that allows for the multiplication of organisms , and is exacerbated by stress . 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 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 are at high risk for colic 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 . 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 than regular horses , and are also at higher risk of developing equine metabolic syndrome . 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 ) . 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 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 . 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 . 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 . they only need to eat 1 . 5 % of their body weight per day in dry matter . it is not fully understood why donkeys are such efficient , 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 . 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 . 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 be 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 . ( see illnesses related to improper feeding below ) it is also important to never give a horse feed that was contaminated by the remains of a dead animal . this 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 . horses may also eat in undesirable ways , such as bolting their feed , or eating too fast . this can lead to either choke or colic under some circumstances . dental issues horses ' teeth continually erupt throughout their life , are worn down as they eat , and can develop uneven wear patterns that can interfere with chewing . for this reason , horses need a dental examination at least once a year , and particular care must be paid to the dental needs of older horses . the process of grinding off uneven wear patterns on a horse 's teeth is called floating and can be performed by a veterinarian or a specialist in equine dentistry . illnesses related to improper feeding colic , choke , and laminitis can be life - threatening when a horse is severely affected , and veterinary care is necessary to properly treat these conditions . 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 . it can occur due to any number of digestive upsets , from mild bloating due to excess intestinal gas to life - threatening . 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 . 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 . horses are also susceptible to laminitis , a disease of the lamina of the hoof . 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 . 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 orthopedic disorders , including osteochondrosis ( ocd ) , angular limb deformities ( ald ) , and several conditions grouped under the popular term " contracted tendons . " if not properly treated , damage can be permanent . however , they can be treated if caught in time , given proper veterinary care , and any improper feeding practices are corrected . young horses being fed for rapid growth in order to be shown or sold as yearlings are at particularly high risk . adult horses with an improper diet may also develop a range of metabolic problems . moldy or dusty hay fed to horses is the most common cause of recurrent airway obstruction , also known as copd or " heaves . " this is a chronic condition of horses involving an allergic bronchitis characterized by wheezing , coughing , and labored breathing . " tying up " equine rhabdomyolysis , also known as " tying up " or , is a condition to which only some horses are susceptible and most cases are linked to a genetic mutation . 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 .