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Purdue University Cooperative Extension

Nutritional Management for Horses

Mark A. Russell, PhD, Department of Animal Sciences and
Penny M. Bauer, DVM, Department of Veterinary Clinical Sciences

The basic nutritional management for horses should be the same, whether you are feeding a horse to win a 4-H show, a competitive trail ride, or the Kentucky Derby. The ultimate goal in feeding should be to have a healthy horse able to perform in the desired manner. A horse must have a balanced diet, which includes all the essential nutrients in the proper proportion and total amount. Much of a horse's health depends on the way in which nutrients are delivered and the feeding management.

Table 1, Minimum nutrient requirements of horses, provides a guideline as to how these requirements change among mature horses of four different sizes. The crude protein is expressed in pounds per day; calcium and phosphorus are expressed in grams per day; digestible energy needed per day is expressed in Mcal's per day. Vitamin A is measured and expressed as 1000 International Units (I.U.). Exercise at a moderate level of some trotting and cantering for one hour each day was used.

Table 1. Minimum daily nutrient requirements for mature horses.*

                Mature Digest   Crude       Calcium     Phosphorus    Vit A
                body   energy   protein                               1,000
                lbs. lbs./   %   grams/   %   grams/    %     IU's/
                ___    day    day    of    day    of   day       of     day
                                    diet         diet           diet
Mature horse    440    7.4    .65   8     8      .25     6       .20     6.0
at rest         880    13.4   1.18  8     16     .25     11      .20     12.0
(maintenance)   1100   16.4   1.45  8     20     .25     14      .20     15.0
                1980   24.1   2.13  8     36     .25     25      .20     27.0

Mature horse    440    11.1   .98   10    14     .30     10      .25     9.0
at moderate     880    20.1   1.77  10    25     .30     17      .25     18.0
work**          1100   24.6   2.17  10    30     .30     21      .25     22.0
                1980   36.2   3.20  10    44     .30     32      .25     40.0

Mares, last     440    8.9    .86   11    17     .50     13      .40     12.0
30 days of      880    16.1   1.56  11    31     .50     23      .40     24.0
pregnancy       1100   19.7   1.91  11    37     .50     28      .40     30.0
                1980   29.0   2.81  11    55     .50     42      .40     54.0

Mares, peak     440    13.7   1.52  13    27     .50     18      .35     12.0
of lactation*** 880    22.9   2.52  13    45     .50     29      .35     24.0
3 months        1100   28.3   3.15  13    56     .50     36      .35     30.0
                1980   45.5   5.67  13    101    .50     65      .35     54.0
*  From Nutrient Requirements of Horses, 1989, National Research Council.
** Examples are horses used in ranch work, roping, cutting, barrel racing,
   jumping, etc.
***Lactation level is assumed to be 3% of body weight/day.
Protein is needed by the horse for growth, muscle development, reproduction, lactation, repair of body tissues, and skin and hair development. If energy in the diet is low, protein can also be converted to energy. It is necessary to consider the quality of the protein (the content of essential amino acids) as well as the total amount of protein fed. The lysine (an indispensable amino acid) requirement for weanlings is .6-.7% of the diet and for yearlings .5% of the diet.

No other amino acid requirements have been determined. Horsemen must rely on legume hay or quality concentrate feeds to provide the balance of amino acids needed. Commercial feeds containing urea, a non-protein nitrogen source, should not be fed to horses because the horse is unable to utilize non-protein nitrogen to the degree that cattle can. Feeding excessive protein to horses with the belief that it will increase muscle development is not valid and is very expensive. Excess protein (that fed above the requirement) is broken down into energy (calories) and a nitrogen by-product called urea, which is excreted in the urine causing the horse to urinate and drink more.

Vitamins play a variety of roles in the body, and quite often they are catalysts for metabolism. While only a minute amount of each may be needed, a deficiency can cause severe side effects or illness once the reserves are depleted. Vitamins are classified into two groups. The fat-soluble vitamins, which can be stored in the body for future use, are A, D, E, and K. Because they are stored, toxicities can occur if fed in excess. The water-soluble vitamins, which are not stored and must be supplied continually are the B-complex vitamins. Many vitamin supplements are available, but should only be used after determining that the horse's diet needs to be supplemented. Never supplement vitamins in amounts which greatly exceed the daily requirements. Be especially conscious of levels of the fat-soluble vitamins being fed. In general, a good, balanced diet of green hay, grain, and sunlight will provide adequate amounts of vitamins for the horse unless under a large degree of stress.

Mineral content of a horse's diet is determined by the soil and water in the area, the quality of feed, and the proportion of grain to hay in the diet. The main minerals are often classified as macro minerals. These are Calcium (Ca), Phosphorus (P), Sodium (Na), and Chlorine (Cl). Depending on the area, trace minerals of concern are Iodine (I) Iron (Fe), Selenium (Se), Zinc (Zn), Manganese (Mn), and Copper (Cu). These trace or micro-minerals are also referred to as electrolytes.

Table 2. Minimum daily nutrient requirements for growing horses. *

Cur      Cur    Expt'd  D.E.    Crude Protein  Calcium Phosp              Vit A
age      body   daily   M.Cal/  lbs/   (%)     grams/  (%)    gram/  (%)  1,000
(Mo.)    weight gain    day     day            day            day         IU's/
Growing horses **
440 lb mature 
4        165    .88     7.3     .81    16      16      .70     9      .50     3
12       308    .44     8.7     .86    14      12      .55     7      .40     6
18NT***  374    .22     8.3     .83    13      10      .45     6      .35     8
24T****  407    .11     11.4    1.07   12      13      .45     7      .35     8

Growing horses
880 lb mature 
4        319    1.87    13.5    1.49   16      33      .70     18     .50     7
12       583    .88     15.6    1.55   14      23      .55     13     .40    12
18NT     726    .55     15.9    1.58   13      21      .45     12     .35    15
24T      803    .33     21.5    2.02   12      27      .45     15     .35    16

Growing horses
1100 lb mature 
4        385    2.00    14.4    1.59   16      34      .70     19     .50     8
12       715    1.10    18.9    1.88   14      29      .55     16     .40    15
18NT     880    .77     19.8    1.97   13      27      .45     15     .35    18
24NT     990    .44     26.3    2.47   12      34      .45     19     .35    20

Growing horses
1980 lb mature 
4        605    2.86    23.1    2.55   16      53      .70     29     .50    12
12       1100   1.98    31.2    3.10   14      49      .55     27     .40    22
18NT     1463   1.54    33.6    3.34   13      49      .45     27     .35    30
24T      1672   .99     42.2    3.96   12      61      .45     34     .35    34

*    From Nutrient Requirements of Horses, 1989 National Research Council.
**   Moderate rate of gain. 
***  Long yearling (18 month) not in training.  
**** Two year old (24 mo) in training.
Table 2 shows the requirements for growing horses of four different mature sizes. The 18 month old, long yearling example is not in training, and the 24 month old is in training. The daily gain expected indicates the growth rate expected. The growth rates used are moderate. There is plenty of research to associate faster growth rates with bone disorders.

Salt (NaCl) aids the body in fluid and temperature regulation. In hot weather, the temperature of the body is controlled by sweating. Water, salt, and other minerals are given off and need to be replenished. The salt intake of a horse is directly proportional to the water intake. It is vital to have salt available for horses either as a block, loose, or mixed in the feed. This is best done in the form of iodized salt or trace-mineralized salt. Allow free access to loose or block trace mineralized salt with selenium as horses will consume the amount they need as long as they have access to plenty of water. All horses require about 1 ounce of salt daily that provides at least .1 ppm of selenium in the total ration. Improper dietary levels of these trace minerals, especially Cu, Zn, Fe, and Mn are thought to contribute to developmental orthopedic diseases such as osteochondrosis desecans (OCD), physitis, and contracted tendons.

The amount of Calcium and Phosphorus, and the ratio between these two elements are vital to bone development and maintenance. The ideal calcium to phosphorus ratio is 1.5:1.0. The ratio of Ca to P in the diet should be between 1:1 and 3:1 for all horses. Adult horses can tolerate a ratio up to 6:1 before problems occur, but growing animals have trouble on Ca:P ratios above 3:1. A supplement with more phosphorus than calcium should be used when feeding good legume hay and no grain. With a deficiency of calcium or an imbalance of the two elements, the horse's bones will become soft and weak or simply won't develop properly.

Table 3. Minerals and vitamins for horse rations. *

                       --------Adequate levels----------
                     Maintenance     Growth and       Working        Maximum
                                     broodmares                      tolerance
  Sodium, %             .10               .10             .30             3.%
  Chloride              .3                .40             .40             5.%
  Magnesium             .10               .1              .15             .5
  Sulfur,%              .15               .15             .15             1.25%
  Iron ppm**          40                50              40             1000
  Zinc ppm            40                40              40              500
  Manganese ppm       40                40              40             1000
  Copper ppm          10                10              10              800
  Iodine ppm            .1                .1              .1              5.0
  Cobalt ppm            .1                .1              .1             10
  Selenium              .1                .1              .1              2.0
  Flourine ppm         --                --              --              50
  Vitamin A IU/lb    910              1667             910             7273
  Vitamin D IU/lb    135               135             365             1000
  Vitamin E IU/lb     25                37              37              450
  Thiamine ppm         3                 3               5             3000
  Riboflavin ppm       2                 2               2               -- 
*  NRC, Nutrient Requirements of Horses, #6, 5th Ed., 1989
** Parts per million (ppm) = mg/kg = mg/2.2 lb


The nutrient requirement for a horse depends on the activity or function the horse is expected to perform. Nutrient requirements are usually quoted for five specific physiological classes: maintenance, growth, lactation (nursing), gestation (pregnancy), and work. The weight of an animal influences its requirement regardless of the function. It is, of course, possible for a horse to be in more than one of these classes at the same time and in these cases, the ration must be altered to meet the requirements for both functions. The desired body condition also affects the requirements. Some horses have a slower metabolic rate and are called "easy keepers," while others always seem to need more than the average required energy and are called "hard keepers."

A maintenance ration is that on which a mature idle horse will maintain normal weight, or condition score under average climate conditions while doing nothing. It should be remembered that extreme cold climatic temperatures (less than 20 degree F) cause the horse to use energy to control body temperature. Work causes the energy requirement to increase. As the intensity or duration of the work increases from light to moderate to intense, the requirements for energy increase 25%, 50%, and 100% above maintenance, respectively.

Lactation and growth increase demands for protein, minerals, and vitamin A as well as energy. With any sort of activity, especially lactation, the Ca and P needs are increased. There is a critical need for increases in protein, minerals, and vitamin A during the last three months of gestation. Energy requirements during the ninth, tenth, and eleventh months of gestation increase 11%, 13%, and 20% respectively. A young foal, while nursing the dam, is drinking about 22% protein, 16% fat, and 58% carbohydrates. It is necessary to keep young foals on a high-protein and high-energy diet. As they get older their need for high protein will decrease.

A horse being maintained can meet its requirements on good pasture or hay only; however, as more is expected from a horse, its nutrient requirements increase.


Horse rations are usually made up of hay or pasture plus grain or concentrate. The idle horse has a low-energy requirement and can meet its needed level of nutrients on pasture and free access to water and mineralized salt. In order for the pasture to provide the majority of the nutrients for a horse for a year, owners must allow two to three acres per horse.

Most horses will eat about 2.5 pounds of air-dried feed per 100 pounds of body weight per day. This depends on the feedstuff's quality and dry matter composition, but a 400 lb. horse eats about 10 lbs. of feed per day, and a 2000 lb. horse eats about 50 lbs. of feed per day. To maintain normal digestive processes in the large intestine and to avoid boredom, all horses should receive at least 1 pound of forage per day per 100 pounds of body weight. This can be supplied by pasture, long hay, or cubes with at least a three quarter-inch particle size. The pelleted products can cause digestive problems when fed alone. In addition, a diet consisting solely of pellets results in less time spent eating and can lead to boredom and increased wood chewing.

Table 4. Composition of some common horse feedstuffs. *

                        Dry**   D.E.**  C.P.**  Ca**    P**     Vit.A**
                        Matter% MCal/lb lb/lb   g/lb    g/lb    1000IU/lb
 Alfalfa, early bloom   90.5    1.02    .18     5.81    .86     23.00
   Full bloom           90.9    .89     .155    4.90    .99     10.74
 Clover, red            88.4    .89     .132    5.53    .99     9.88
  Early bloom           89.1    .88     .114    1.09    1.36    6.08
  Late bloom            90.6    .78     .076    1.09    1.22    3.29
  Mid-bloom             87.6    .85     1.26    1.13    1.13    2.45
  Early bloom           89.1    .83     .096    2.04    1.13    8.51
  Late bloom            88.3    .72     .069    1.54    .59     7.23
  Full bloom            91.9    .86     .1181   .81     1.32    8.73
  30% legume            89.0    .93     .1332   .66     1.10    11.72

 Barley                 88.6    1.49    .117    .23     1.54    .37
 Corn                   88.0    1.54    .091    .23     1.27    .98
 Oats                   89.2    1.30    .118    .36     1.54    .02
 Wheats. red            88.4    1.55    .114    .14     1.77    __
 Wheat bran             89.1    1.33    .154    .59     5.13    .48
 Soybean meal           89.1    1.43    .445    1.59    2.86    __
 Linseed meal           90.2    1.25    .346    1.77    3.63    __
 Molasses (blackstrap)  74.3    1.18    .043    3.36    .36     __
 Vegetable oil          99.8    4.08    __         __      __   __

Mineral Supplements
 Limestone, CaC03       100     __      __      178.67  .18     __
 Oystershell            99      __      __      170.64  .31     __
 Bone meal, steamed     97      __      __      135.12  56.58   __
 Rock phosphate, defl.  100     __      __      145.15  81.65   __
 Dicalcium phosphate    97      __      __      96.81   83.73   __
 Sodium triphosphate    96      __      __         __   108.86  __
*  Derived from nutrient requirements of Horses 5th Ed. N.R.C. 1989.
** All nutrients are expressed on an as fed basis.
Hays vary greatly in quality. Quality depends on the maturity of the plant when harvested, extent of mechanical damage, and the method used in drying. Legume hays (alfalfa, lespedeza, birdsfoot trefoil, and clover) provide higher levels of protein, calcium, and vitamin A (carotene) than do grasses. Grass hays (timothy, orchardgrass, fescue, and smooth bromegrass) are lower in calcium and protein and higher in fiber than legumes. Where both legumes and grasses are available, a mixed hay is an ideal forage for horses. Table 4 on the previous page shows that as the plant matures, it becomes less nutritious and looses digestibility. All hay is best harvested before one-half of the plants have headed out or bloomed. Pure legume hays should be fed to growing foals and lactating mares, because of their very high calcium and protein requirements. Pure alfalfa may be too rich in energy and protein for performance, and has more calcium than is needed for pregnant mares. Table 4 gives the composition of various common horse feeds. Energy content is expressed in Mcal's per lb. and protein, Ca and P are expressed as amount of nutrient per pound of feedstuff.

As more performance (work) or growth is expected of an animal, a proportionately larger amount of concentrates must be fed. Generally, most of the energy, phosphorus and some of the protein must come from the concentrate. Oats are a popular grain for horses because they are palatable and have a high protein and fiber level. Corn is another popular grain to use in horse rations. It is high in energy but low in both the quantity and quality of protein. Corn is often referred to as a heavy grain because it is denser and higher in energy per unit weight than oats. Corn is usually the most economical energy source.

Grains (and all other feeds) should be fed by weight rather than by volume. The nutrients are expressed "per pound," thus, it is necessary to know how many pounds are being fed. It is beneficial to crack, roll, or crimp grains to break the outer shell thereby allowing more efficient digestion and use of the grain. But this is not inexpensive and often it is more economical to feed 5 to 6% more whole grain. Processed grains are dustier and don't store as well for extended times as whole grains. Bran has traditionally been added to horse diets to serve as a fiber source and a laxative. It can serve as a good source of energy and protein, but usually it is added at very low levels and the fiber content is negligible compared to hay. It would be more economical to feed corn and soybean meal than bran.

Other concentrates are commonly added to horse rations to increase protein level. Soybean oil meal and linseed oil meal are two of the most common sources. When compared to soybean, linseed oil meal does not have as good a quality protein as it is lower in lysine. There are many excellent commercial feeds that are already balanced specifically for horses. Usually these have the vitamins and minerals added; but to be safe, check the bag content label or ask the dealer for a composition profile. Most horseowners should rely on the expertise of commercial feed companies and purchase concentrates designed for the specific category of horse. Often the convenience and quality is well worth any cost increase. It is wise to blend needed vitamins, minerals, or protein supplements into the concentrate mixture, thereby knowing exactly what the horse is getting each day.


The major factors to consider when formulating rations are the class of animal being fed (function, weight, age, etc.) and the kind of forage available. A good ration will start with a high-quality forage. Large amounts of grain will not fully compensate for poor quality hay. It is more economical and better for the health of the horse to have a good quality hay or pasture as the foundation of the feeding program. Then supplement the hay ration with concentrates and minerals as it is necessary. Feed is not 100% nutrients. Common feeds range from 85-92% dry matter and the rest is water. Only the dry matter contains nutrients.

The nutrient composition is vital but no more so than the way the ration is delivered. Use as much good forage as possible; feed clean, dust- and mold-free feedstuffs that are free of any toxic weeds.

It should be emphasized that the effects of a ration should be closely observed for at least two weeks to determine any changes in the animals' condition or eating behavior. Calculations alone do not ensure success. Individual variations among horses must also be kept in mind, and the ration may have to be altered for "easy keepers" or "hard keepers." Differences may be influenced by temperament, previous nutrition, size, age, and weather conditions.

This discussion refers only to the "normal" or "average" horse and should be used only as a guideline. Proper individual feeding still depends on the feeder's careful observation and good judgment. The owner also needs to determine what body fat condition score they desire. This will change the requirement as much as the other factors mentioned. Calculations cannot replace good horsemenship.

The most serious nutritionally related problems in mature horses are colic and founder. Colic, or abdominal pain, is often associated with impactions and twisted intestines in the horse. Sudden changes in feedstuffs and diets with low-fiber content or small particle size are frequent causes. Laminitis, on the other hand, is a disease of the hoof that causes severe lameness. There are many causes of laminitis (founder), but overeating high-energy concentrates is probably the most common.

Research indicates that maximal rate of gain is not necessarily associated with maximal soundness. The energy density of the ration seems to be the culprit, combined with mineral imbalances. Developmental orthopedic diseases including physitis, OCD, and contacted tendons are problems most commonly associated with fast growing foals. These problems can be minimized by decreasing the rate of gain (decreasing energy intake) and by paying close attention to mineral balances, protein levels, and plenty of exercise.

The following feeding management practices assist horsemen in achieving good results with minimal problems.

Feed Requirement Worksheet*

                                        Class of Horse___________________

Owner's Name____________________        _____Mature horse at rest

Address_________________________        _____Mature horse at moderate work

Breed of Horse____________________      _____Mare in last 90 days of pregnancy

Weight of Horse__________Age______      _____Mare in peak of lactation 
                                             (first 3 months)

                                        _____Growing foal ______Mature weight

                   Dig Energy  Dig        Ca          P           Vit A
                               Protein                            1000
A. Your horse's
   daily           _____Mcal   _____lb    _____g      _____g      _____IU's
       I           II           III        IV          V           VI

B. Ration   lbs of X(Mcal/lb)  X(C P/lb)   X(Ca/lb)    X(P/lb)  X(1000 IU's/lb)

Feedstuff   each   =Mcal       =lb C P     = g Ca      = g P       = 1000 IU

________   _____   X(___)=___  X(___)=___  X(___)=___  X(___)=___  X(___)=___

________   _____   X(___)=___  X(___)=___  X(___)=___  X(___)=___  X(___)=___
________   _____   X(___)=___  X(___)=___  X(___)=___  X(___)=___  X(___)=___
________   _____   X(___)=___  X(___)=___  X(___)=___  X(___)=___  X(___)=___
________   _____   X(___)=___  X(___)=___  X(___)=___  X(___)=___  X(___)=___
C. Total   ___lb   _____Mcal   _____lb     _____g      _____g    ____1000 IU's
   supplied by
D. Horse's         _____Mcal   _____lb     _____g      _____g    ____1000 IU's
E. Needed          _____Mcal   _____lb     _____g      _____g    ____1000 IU's

F. Instructions
1. Determine the class of horse and record requirements from Table 1 and 2 in line A.
2. List ration ingredients and pounds of each in the appropriate columns.
3. Be sure ration ingredients in B do not exceed 2-2.5% of body weight.
4. Obtain feed compositions from Table 4 and record in cols. II, III,  IV, V, and VI.
5. Multiply lbs of each feed (col. I) times each value in cols. II,  III, IV, V, and VI.
6. Total the nutrients from each source to get total in ration (line C  values).
7. Copy nutrient requirements from line A to line D.
8. Subtract line C values from line D values and record any deficiencies in line E.


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