Basic Dietary Requirements
Like all animals, horses need the basic nutrients; proteins, energy-producing compounds (carbohydrates and fats), vitamins, minerals and water. Because of their unique digestive systems, horses also need fiber, or bulk in their rations. Fiber consists of indigestible components in the ration, which keep the digesta flowing properly, and components digested in the hindgut, which provide about 70% of the horse’s energy requirement when horses are fed high-forage rations.

Why Are Forages Necessary for Horses?
Forages (grass and hay) are the natural feed for horses due to the structure and shape of the equine digestive tract. Forages contain suitable amounts of protein and energy-producing compounds and large amounts of digestible and indigestible fiber, in varying amounts depending on the type of forage and the stage of maturity at harvest. Forages should be used to provide as much as possible of the three nutrients (dry matter basis) needed in the largest quantities; energy, protein and fiber or bulk. Fresh forages (pasture grasses) also contain about 70% water and can provide most of a horse’s water requirement in some situations. However, horses should always have fresh, clean water available free choice, since dehydration predisposes horses to colic. Forages are extremely variable in vitamin and mineral content and should not be relied upon to meet the total needs for those nutrients. Figure 1 illustrates the deficiencies of minerals in typical alfalfa hays, grass hays and cereal grains.

Figure 1  Deficiencies in Mineral Content of Common Horse Feeds When used in horse rations : Typical alfalfa hays are deficient in: P, Na, Se, Cu, Zn, Mn, Fe Typical grass hays are deficient in: Ca, P, Mg, Na, Se, I, Cu, Zn, Mn, S Typical cereal grains are deficient in: Ca, P, Na, K, Se, I, Cu, Zn, Mn, Fe, Co (NRC, 1989). Minerals in red are not contained in trace-mineralized salt blocks

All feeds must be processed by the digestive tract before absorption. Horses have a digestive tract suited to processing large amounts of good-quality forage (See Equine Nutrition in the 21st Century Part One). One of the most widespread myths in horse nutrition is that ‘horses should be fed 1% of their body weight in forage each day.’ This comes from a common statement, “Horses should be fed at least 1% of their body weight in forage each day,” which has been changed into the former interpretation. The emphasis on concentrate feeds due to marketing efforts has also helped to produce rations containing less forage than is desirable. Many people get the impression that all of the ‘good stuff’ is in the feed and the hay is ‘just the filler.’

In fact, people should very rarely actually feed only 1% of body weight of forage to horses. This is the bare minimum, in the short term, to prevent digestive disorders. It applied to nursing foals, which are still getting most of their nutrients from milk, and to race horses and other extreme performance horses in the past, when only hays and grains were available to provide energy. Modern feeds with added fat and digestible fibers provide more energy per pound and allow horses to eat at least 2% of body weight of forage in most situations. In a recent research study, mature geldings on pasture voluntarily consumed 3.3% of their body weight in dry matter from pasture, or over 100 pounds of pasture grass (as fed basis), per day. The capability of horses to digest and utilize forage for energy has been seriously underestimated in the past, leading to boredom and the associated vices in horses.

It is important to provide at least 1.5% of body weight in dry weight of forage for weanlings and yearlings and 2-3.5% for mature horses each day. This means 7.5 pounds of hay for a 500-pound weanling and 20-35 pounds of hay for a mature horse, the lower amount for overweight horses and the upper amount for hard-working horses and lactating broodmares. When we feed less forage than this, we greatly increase the risks of a number of digestive disorders, including colic, founder, ulcers, tying-up, cribbing and developmental orthopedic diseases. Some feeds, such as very low fiber/high starch grains, produce negative results in the digestive tract because they are so different from the natural diet of the horse, which is good-quality forage.

All forages are not created equal
One of the most important aspects of horse feeding and management is to choose the correct forage for each horse and feed the correct amount to each horse. Figures 2 and 3 illustrate nutrient content in forages from two different sources.

Figure 2..... Nutrients in Forages #1*

Forage Type	Protein %	Calcium %	Phosphorus %	DE Mcal lb	TDN %
Alfalfa	15-20	0.9-1.5	0.2-0.35	0.8-1.1	48-55
Red Clover	13-16	0.8-1.5	0.2-0.35	0.8-1.1	46-52
Orchardgrass	7-11	0.3-0.5	0.2-0.35	0.7-1.0	42-50
Timothy	7-11	0.3-0.5	0.2-0.35	0.7-1.0	42-50
Bermudagrass	6-11	0.2-0.4	0.15-0.3	0.7-1.0	42-50
Tall Fescue	5-9	0.3-0.5	0.2-0.35	0.6-0.9	40-48
*NRC, 1989; UK Equine Nutrition Program, 1999

Figure 3.....  Nutrients in Forages #2*

Forage Type	Protein %	Calcium %	Phosphorus %	DE kcal/lb	ADF %
Tall Fescue	9.3	0.75	0.17	790	38.1
Timothy	11.3	0.46	0.26	880	33.1
T/A cubes	14.1	0.87	0.19	850	37.0
Mixed Alfalfa	13.7	0.99	0.20	880	37.9
Alfalfa	18.1	1.13	0.26	1030	29.6
Alfalfa cubes	17.5	1.15	0.22	1000	39.7
*Examples from analysis, ADM Alliance Nutrition

Forages should be chosen based on forage type, local availability and value (cost compared to nutrients provided). The basic steps in forage selection are:

1. Determine the horse’s requirements for protein and energy
2. Determine the maximum amount of forage the horse can consume in one day
3. Research local forage options
4. Compare values of available forages
5. Choose forage(s) that will provide as much of the horse’s protein, energy and fiber
    needs as possible in an amount the horse can easily consume in one day, but will
    keep him occupied as much as possible (to reduce boredom)
6. Supplement the forage(s) with a broad-spectrum vitamin/mineral supplement and/or
    fortified feed to make sure vitamin/mineral needs are met, since forages vary greatly
     in these nutrients and never completely meet horses’ needs.

Types of Forages - Legumes and Grasses
Forages for horses are broadly classified as grasses or legumes. Legumes are plants that are able to obtain nitrogen from the air because of bacteria living in nodules in their roots. This process, called ‘nitrogen fixing,’ increases the protein content of the plants and, therefore the animals that graze on them. Examples of legumes fed to horses are: alfalfa, clovers, birdsfoot trefoil and lespedeza. Peas and soybeans are legumes whose ‘seeds’ are popular in human diets.

Grasses* are plants in the family, Gramineae, and are not capable of nitrogen fixing. Examples of common grasses fed to horses are: Kentucky bluegrass, timothy, orchard grass, brome grass, reed canary grass, matua or prairie grass, garrison grass, tall fescue, perennial ryegrass and coastal bermudagrass. Cereal grain plants such as oat, winter wheat and barley are grasses when harvested during early growth before the grains mature and the stems turn to straw. They are called ‘cereal grasses,’ the most popular of which is probably oat hay, which contains green stems and leaves plus oats in the soft dough stage (see below). Grasses are more palatable when fresh and easier to make into hay than legumes. Grasses generally require nitrogen, phosphorus and potassium fertilization and a soil pH of 6.0-6.5. For help analyzing and improving your pasture, contact your local Cooperative Extension Service. Grasses should be cut in the early-head stage for the best feed-value. Figure 4 illustrates the changes in nutrient content of oat hay at various growth stages.

Figure 4.........  Oat Hay Growth Stage*

Stage	Protein % of DM	Phosphorus % of DM	Potassium % of DM	Calcium % of DM
50% headed	15.6	0.23	2.3	0.32
Fully headed	14.9	1.23	2.2	0.33
Milk	12.2	0.19	1.6	0.27
Soft dough	12.2	0.18	1.6	0.28
Hard dough	11.5	0.18	1.5	0.31
Mature	10.8	0.17	1.2	0.28
*In Hintz; adapted from Erickson et al., 1976, North Dakota Farm Research.

Grass Pastures - When on pasture, horses create ruffs (where they urinate, defecate and do not eat) and lawns (where they graze and often over-graze). They choose to eat the shortest plants, because they are the richest in nutrients, even though it is frustrating to us when they seem to ‘waste’ the larger plants in the rough areas. Grass pastures should be clipped about every 30 days to even out the roughs and lawns. Grass pastures need 14-30 days to recover after close grazing. Therefore, rotation of horses between pastures will improve the life span and usefulness of the pasture.

Hay Quality
Hay quality is as important as forage quantity. Hay should have a crude protein content of 7% or higher on an as-fed basis. Hays with less protein tend to be over-mature and have too much indigestible fiber. As plants mature, their digestibility and nutrient content decline as illustrated for first cutting timothy hay in figure 5 and alfalfa hay in figure 6.

Figure 5......Harvest Date of Timothy Hay*

Date of Harvest	CP %	NDF %	ADF %	Cellulose %	Lignin %	OM % Digest.
June 17	22	49	27	20	4	80
June 23	16	50	27	21	4	80
July 1	13	61	33	27	5	74
July 7	11	64	36	30	5	71
July 13	10	64	37	30	6	68
July 20	8	64	38	31	6	63
*First cutting Timothy, DM basis In Hintz, 1983; adapted from Lindgren, Swedish J. Agric. Res. 10:3-10, 1980.

Figure 6......Stage of Maturity of Alfalfa Hay*

Date of Harvest	Stage of Maturity	Crude Protein, %	Dry Matter Digestibility, %
May 31	Vegetative	21	66
June 5	Early bud	20	65
June 10	Bud	19	63
June 15	Early bloom	18	61
June 20	Quarter bloom	17	60
June 25	Half bloom	16	58
June 30	Full bloom	15	57
*In Hintz, 1983; adapted from M.J. Anderson, Utah Sci., 1975

Pasture and grass hays can often be offered free choice. Legume hays usually cannot be fed free choice, because they contain too much protein and energy for most horses compared to their bulk content. When feeding legumes, you should use little or no grain or concentrate in your total rations, or your horses will become overweight. Vitamins and minerals are still required for all horses.

Benefits and Shortcomings of Specific Forage Species in Horse Rations
Following are some comments about specific kinds of forages for horses**.

Grass Forage Species

Kentucky Bluegrass - Kentucky bluegrass is durable and palatable and has few nutritional problems for horses. It is winter hardy, but does not grow well during hot weather. It is somewhat slow to establish, but tolerates close grazing and controls erosion. It is very popular on the Thoroughbred farms in central Kentucky and surrounding areas. Kentucky bluegrass makes poor-quality hay, so it is seldom made into hay.

Orchard Grass - Orchard grass grows fast in late spring and continues to grow in hot weather. It will not take close grazing or tramping, and it requires good drainage. The palatability of orchard grass decreases rapidly as the plant matures. If made into hay, it works best when mixed with alfalfa.

Tall Fescue - Tall fescue is a very common native grass in the central United States. It is not highly palatable. It grows early and late in the growing season and can be used for winter grazing. It grows in poorer soil and in wetter soil and withstands a lot of abuse. It usually contains an endophyte fungus which improves its ability to thrive, but is very detrimental to broodmares, because it interferes with reproductive hormones. Mares on infected fescue suffer from lengthened gestation, thick fetal membranes and lack of milk production. If not treated, their foals usually die. Do not feed infected fescue to broodmares during the last 90 days of gestation or during lactation. If you suspect fescue toxicity in a mare, contact a veterinarian immediately. Some adverse effects of endophyte-infected fescue have also been reported in growing horses and working horses. There are some types of endophyte-free fescue. Contact your local Cooperative Extension Service for more information.

Timothy - Timothy is the most palatable of the grasses. It is easy to seed and establish, but grows only in late spring and the fall. It will not tolerate close grazing or tramping and is susceptible to weeds. If made into hay, it works best with red clover. High quality timothy/alfalfa cubes are available in some locations (800-680-8254).

Perennial Ryegrass - Perennial ryegrass is easy to establish and has palatability about equal to Kentucky bluegrass. It has a long growing season in cool, moist weather, but is not heat or drought tolerant. A mold, which causes ‘blind staggers,’ can grow at its base.

Coastal Bermudagrass - Coastal bermudagrass is the most important summer pasture grass in the southern United States. It is a warm weather grass that is well adapted to most soils. It creates a dense turf and tolerates heavy traffic but requires drained soil.

Oat Hay - Oat hay is a major annual forage in the western United States and Canada. It is cut in late milk to early dough stage. If cut with fully developed oats, rodents are a problem in the baled hay (straw) (see figure 4 above). Oat hay might contain toxic levels of nitrates, which are made into nitrites by bacteria. Nitrites can change hemoglobin to met-hemoglobin in the blood, preventing it from transporting oxygen. Oat hay has more phosphorus and starch than most grass hays, so it is not suitable for starch-sensitive horses.

Legume Forage Species
Legumes are not very palatable as fresh plants (pasture grass), but are very palatable as hay. All except white clover require close maintenance. They require phosphorus and potassium fertilization and a pH of 6.5-7.0. Legumes should be cut in early-bloom stage for the best value. They should be cut about every 30-35 days and have about the same amount of time to recover. Legumes can lose quality due to leaf loss during the hay making process if sun cured on the field. Dehydrated products retain more leaves during processing. Sun-cured and dehydrated hay cubes are available in cubed and pelleted forms (alfalfa). For information about hay cube availability, call 800 680-8254.

Alfalfa - The most productive and popular legume, alfalfa, is a highly nutritious and a high yield crop. It grows during hot, dry times, but requires good drainage and soil fertility. It requires a soil pH of 6.5-7 and cannot survive close grazing and tramping. It works best as hay or in rotation grazing systems. Alfalfa hay should be checked closely for blister beetles if made in the southern 2/3 of the United States. Blister beetles swarm and feed on alfalfa flowers. If caught in hay crimping and/or baling equipment, the beetle carcasses can cause deadly poisoning in horses.

Red Clover - Red clover is almost equal to alfalfa in nutrient value. It is easy to establish, tolerates acid soils and will grow some in hot, dry weather, but must be reseeded every other year. It is hard to cure and make into hay due to the long time required to dry, but works well with timothy for hay. It might contain a fungus that causes ‘slobbering.’

White Clover - White clover is used in pastures as a nitrogen source for grasses. It reseeds itself and is winter hardy. Its nutritional value is comparable to alfalfa. Ladino is a larger variety of white clover that is not as durable. White clover can also contain the fungus that causes slobbering.

Other Legumes - Birdsfoot trefoil has a nutrient value about equal to alfalfa, but is not as productive. Alsike clover should be avoided because it causes photosensitization (especially on the white markings of horses) and liver damage in horses. Sweet clovers, if not cured properly, may contain dicumerol, which has anti-vitamin K activity and prevents blood clotting. Lespedeza is not highly productive and has tough stems, but is heat tolerant.

Nutrients in Forages
Energy from Forages - Generally, grasses provide about 0.6-0.9 Mcal/lb digestible energy (DE) to horses. Legumes provide about 1.0-1.1 Mcal/lb DE. Some forages have properties that make them unsuitable as energy sources for horses. Lush, early-spring grasses can be high in fructan, a starch-like carbohydrate that is not digested in the foregut of horses, but proceeds to the hindgut and causes starch overload symptoms including colic and founder. Poor-quality forage of any type can have low digestibility (high indigestible lignin fiber content) and contribute to a ‘hay belly.’ Many forages have toxic properties.

Protein in Forages - Fresh grasses contain about 12-18% protein in the dry matter. Fresh legumes contain about 15-22% protein in the dry matter. When made into hay, grasses contain about 6-14% protein on an as-fed basis and legume hays contain about 12-20% protein as fed. Of course, maturity of the plants when eaten or harvested is the greatest factor affecting their quality.

Minimum Protein Needs of Horses range from 8.5 to 18% based on class of horse as illustrated in figure 7. When comparing protein in forages to protein needs of horses, it makes sense that we need to choose the correct forage for each type of horse, then feed the correct amount that allows them to meet their needs, yet stay busy eating for as long as possible, as nature intended.

Figure 7...... Minimum Protein Needs of Horses

• Maintenance 8.5 %

• Pregnancy (last 3 months) 11.0 %

• Lactation (first 4 months) 14.0 %

• Foals (creep feeds) 18.0 %

• Weanlings 16.0 %

• Yearlings (12 months) 13.5 %

• Two-year-olds 10.0 %

            (NRC, 1989)

Water in Forages - Pasture is only 20-30 % dry matter, the rest being water. Properly cured hays contain about 9-11% moisture. Digestive contents of horses are about 90% water until they reach the colon, where water is re-absorbed and fecal balls are formed. Horse feces are about 60% water. Forages absorb more water and hold more water in the digestive tract than grains.

Vitamins in Forages - The vitamin A precursor, beta carotene, is abundant in fresh forages. Legumes and fresh grasses are good sources of vitamin E. Vitamin D is high in sun-dried forages. Vitamins K and B-complex are made by microbes, in the hindgut, during forage digestion. Old and poor-quality forages have minimal vitamin content. Vitamins A and K are lost from hays in 6 months. A six-month supply of vitamin A can be stored in the liver of horses. Excessive work may increase the vitamin E requirement. Stress from constant travel or showing increases vitamin requirements. For more information about vitamins, see The ABC’s of Vitamin Nutrition in the Technical Bulletins Section.

Minerals in Forages - Grasses usually have a calcium-to-phosphorus ratio of about 2:1. However, this can vary greatly. In legumes the calcium-to-phosphorus ratio is often 5:1 or higher. Legumes are also usually higher in trace minerals, but forages alone never meet all of a horse’s mineral needs (Figure 1 above).

Hays usually contain 1-4% potassium, and legume hays usually have the highest values for potassium. The potassium requirement is only about 0.25-0.3% minimum for horses at maintenance. The requirement increases to about 0.6% minimum for hard-working horses. It is important to limit potassium in the rations of horses with Hyperkalemic Periodic Paralysis (HYPP). See Managing Horses With HYPP in the Technical Bulletins Section.

Soils in the U.S. vary from high to low selenium content. Be aware of your soil’s selenium content and supplement it as needed.

Feeds and Heat Production
Metabolism of feeds produces body heat. Metabolism of forage results in the greatest amount of heat, with grains resulting in intermediate heat production and fats the least heat production. Therefore, in winter, it makes sense to increase the forage rather than grain. This is contrary to the old tradition of adding more ‘corn for extra heat’ in the winter. In summer, it makes sense to increase the fat content of the concentrate rather than adding grain.

Forage and Fat
Adding grain results in less forage eaten. And, feeding more than 6 pounds per day of grain-based feeds to horses greatly increases the risks of Equine Grain-Associated Disorders such as colic, founder, gastric ulcers, tying-up and developmental orthopedic diseases. Feeding added fat does not necessarily reduce the amount of forage eaten. Modern rations consisting of forage and fat with less starch and sugar are the best combination for health and performance (refer to parts one-four of this series for more detailed information).

Forage Summary

• Feeding high-forage rations results in healthier horses

• Forages should be chosen to meet as much as possible of horses’ protein, energy and fiber requirements

• Choose the correct forage according to type and workload of horse, local availability, cost and value

• Forages do not provide optimum amounts of vitamins and minerals, so they must be supplemented

 *Grass definition from Feeds & Nutrition Digest. 1990. M. E. Ensminger, J. E. Oldfield and W. W. Heinemann, p 129. **Some specific forage information courtesy of Dr. Robert Kline from a presentation at The Ohio State University. Next in this series, Equine Nutrition in the 21st Century part six – Feeding Horses with Genetic Disorders

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