Ohio State University Extension Bulletin

Horse Nutrition

Bulletin 762-00

Carbohydrates and Fats


Horses will actively seek out sufficient feedstuffs to meet their energy needs. The main sources of energy are fats and carbohydrates. Carbohydrates in the ration are the sugars and starches of the grains and the cellulose (fiber) of the roughage and grain. Fats are the oils and related compounds in the grain and roughage and naturally make up about 2—4% of the ration. A horse can handle a ration higher in fat (as high as 15%) without digestive problems. Rations with more than 15% fat may result in loose stools and have not been shown to improve performance over rations of 12% fat. Fats are necessary in all rations, as they participate in metabolic functions and produce healthy sleek haircoats. Many people add one to two ounces of vegetable oil (such as corn oil) to the daily ration for the purpose of improving the haircoat.

Fats produce 2.25 times more energy per pound than carbohydrates, and when used to produce energy, they produce the least amount of internal body heat. As a result, some endurance horses are being fed as much as a pint of vegetable oil each day when they are working.

The energy needs of a horse are measured in calories. The requirements are expressed as kilocalories (Kcal) or megacalories (Mcal = 1,000 Kcal). Older nutrition manuals use the term Total Digestible Nutrients (TDN) to measure energy. One pound of TDN is roughly equal to 2,000 Kcal of Digestible Energy (DE). Energy is used for maintenance, reproduction, work, growth, and lactation. Tables 1 and 4 give the energy needs for different activities and maintenance. To determine the total energy needs for a horse, add the needs from the different sections of the tables that apply to that particular animal.

Excess carbohydrates or fat causes obesity in the horse, which is detrimental to any animal. The rule of thumb for a horse being in good flesh is that you cannot see the ribs, but you can feel them if you rub your hands across them. Lack of sufficient energy in the diet is the primary cause of a thin horse, so give the horse more feed and increase the grain portion since it contains more energy per pound than roughage. Fat horses need less or no grain, as good quality roughage can meet the needs of most idle mature horses.


Roughages are generally grasses or legumes in either the green or dried state. Pastures and horses are a logical combination from the standpoint of providing both exercise and feed for the horse. However, many horsemen are uninformed when determining what plant species should be in a pasture and how to manage it for maximum feed production. In Ohio it takes from one to five acres of pasture to provide enough feed for one horse during the summer. Under expert management a horse can gain sufficient summer feed on one and a half acres. To have more than one horse for one and one half acres of pasture changes the pasture to simply an exercise lot, or at best only a partial supplier of feed. It will take an additional one to two acres to produce hay for winter feed based on supplying two tons of hay per horse.

In general, it takes about three pounds of green forage to provide the same amount of nutrients found in one pound of dried forage. Roughages for horses fall into those from the grass and those in the legume families.


Grasses commonly fed to horses are timothy, orchardgrass, bromegrass, tall fescue, and Kentucky bluegrass. Table 5 lists the nutrient values for these grasses in the green immature state and also as they would be in hays. In general, grass hays (depending somewhat on time of harvest) are low in protein compared to legume hays. They are also low in calcium and phosphorus, but the two minerals usually are in the correct ratio (2:1). Grass hays are usually easier to harvest than legume hays without them becoming dusty, and they are quite adequate nutritionally for most mature horses.

Of these grasses, fescue is the one that has the most serious problem as a horse feed. Fescue often has a fungus (endophyte) living in it that can cause agalactia (reduced milk production), low feed intake, decreasing rate of gain of body weight, and excessive salivation. This fungus has also been blamed for extra thick placental membranes that often cause death to the foal during birth. Infected fescue grass or hay should not be fed to mares in the last three months of gestation. Infected fescue would also decrease milk production after foaling. There is an endophyte-free fescue seed available, which should eliminate the present problems with fescue if used.


Legumes commonly used for horses in Ohio are alfalfa, red clover, ladino clover, and birdsfoot treefoil. The nutritional values for alfalfa and red clover are listed in Table 5. The values for the other two are very similar to red clover.

Legume hays are generally higher in protein (depending on time of harvest) than the grass hays. They are also higher in minerals, but have an incorrect ratio (often 5:1) of calcium to phosphorus. As a result of the high protein, they are very desirable in the ration of growing animals, but the calcium-phosphorus ratio must be balanced to prevent bone abnormalities.

The legume hays are more difficult to make due to leaf shatter, which can produce dusty hay and/or stemmy less-digestible hay. With modern hay-making techniques and recognition of the nutritional value of legume hays, these hays, especially alfalfa, have come to be the hay of choice for horsemen.

Red clover may have a fungus that grows on it that will cause the horse to salivate excessively. This fungus is most common in clover raised under wet conditions. Feeding horses red clover hay is not recommended if the hay is causing this excessive slobbering. If the horse is taken off the clover hay and fed other hay for a few days, the slobbering will stop without special treatment. This problem occurs also with the white clover common in Ohio pastures during wet seasons. If the pasture is clipped short and allowed to dry out, new growth is usually safe to graze.


Legumes or grasses may be made into silage or haylage. However, it is not recommended that horses be fed silages due to their potential mold content. There have been several cases of horses being killed by being fed moldy silage.

Pasture Value

It is difficult to determine the value of pasture if you need to rent pasture as a feed source. Several formulas have been developed, some of which are given here:

  1. Number of animal units (one unit = 1,000 lb.) times the average price of one ton of hay times a quality factor (quality factors are 0.22 = lush, 0.20 = excellent, 0.15 = fair to good, 0.12 = poor) equals rate per month.

  2. Price of hay per ton divided by 8.5 = rate per animal per month.

  3. Seasonal rate should be 4—6% of the current market value of the pasture land.

Any one of these formulas should give a reasonable rental value for pasture.


These are feeds that contain high levels of one or more specific nutrients. The energy (grains) and protein (meals) supplements fall into this category.


Oats had been considered the No. 1 grain for horses for many years. The characteristics that earned oats this title are its bulkiness, thereby making oats less likely to cause digestive problems, and its higher protein content compared to corn. Although the oat is about 12—13% protein, the quality of the protein is not excellent, and one should not be feeding oats alone to meet protein needs for growing animals.

Oats may be fed whole, rolled, or crimped. Today, the cost of rolling and crimping is not worth the extra nutritional value derived from doing so. If you are buying crimped oats, be sure that the seed coat is only slightly broken. If the oat is completely crushed, most of the nutrients may be lost and you will not get your money’s worth.


Corn has taken over the position of the No. 1 grain fed to horses in recent years mainly because of its low cost and excellent feed value for energy. If you want to fatten an animal, it is easier done with corn than oats and at a lower cost.

Corn can be fed on the cob, as whole shelled corn, or as cracked corn. Actually cracking corn is economically wasteful. Because of the size of the kernel of corn, a horse will chew the grain before swallowing. If a horse is passing a lot of whole kernels in the feces, he is either bolting his feed or may need to have his teeth floated because sharp points are preventing normal chewing. The horse bolting his feed needs to slow down. Large rocks or a salt brick can be placed in the feed pan with the feed. He then has to sort around the objects to get the feed. Another cure is to spread the feed out in a large feed bunk so it takes him longer to pick up the grain.

Corn is about 10% protein, but as with all grains, the protein quality is relatively poor. Corn contains about double the energy that an equal volume of oats contains. This has been the cause of corn getting the repetition as being a "hot feed." When people substituted corn for oats at an equal volume, their horses would sweat more and /or get fat. To eliminate the problem, corn needs to be fed at only half the volume or less than the volume of oats. There has also been a claim among draft horse breeders that corn caused bog spavins in the hocks of draft horses. There is no basis to this claim, except that if you fed too much corn, resulting in overweight horses, and then worked them hard, the added stress on the hock joint could cause bogs. However, the cause was not corn, but excess weight and stress.


Barley has been fed to horses with excellent results. It is about 11—13% protein and should be fed in a rolled or crushed form. The grain in its whole form is too hard and small for the horse to eat safely or digest efficiently. The main reason for not using barley more today is cost of the grain.

Wheat Bran

This by-product of the milling industry is often used as a horse feed. Bran contains about 17% protein, is considered a laxative feed, and is high in phosphorus. The protein is of low quality, the laxative effect is questionable, and the phosphorus content may upset the calcium-phosphorus balance in the feed ration. Also there is a question as to the availability of the phosphorus that is present in bran. Much of it is tied up in an indigestible form, and therefore it is not being used much today for horse feeds.


Molasses has been fed to horses to increase palatability and to decrease dustiness of feeds. The palatability factor is questionable, since horses learn to eat what they are trained to eat. If a horse is used to eating feeds with molasses, it will often refuse other feeds. And a horse that has never eaten feeds with molasses will tend to refuse feeds with molasses. The major use of molasses is to bind fine particles to the grains so that a mixed feed containing all the needed minerals, vitamins, protein, and supplements can be fed without the fine particles settling out. Dry molasses is of no use since it only adds to the amount of fines. Molasses is an energy source, but its cost makes it a poor economic choice as an energy source for horses.

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