Nutrition in Horses

The basis of a horse's diet is roughage (pasture, hay, etc.), so careful attention must be paid to this feature of the diet above all others.

Generally, roughage accounts for 70 to 100 percent of a horse's caloric, mineral and fiber intake. Good quality mixed (legume and grass) pasture under some form of weed reduction program is an excellent way to support horses.

But, more and more, real estate prices and urbanization are leading to the use of hay as the primary source of dietary roughage for most horses in the United States.

The purpose of this section is to provide some basic principles in roughage feeding to horses. Specifics concerning your horse's activity and your local area need to be taken into account to identify the ideal diet, as sometimes certain foods are just not available. Growing, pregnant and working horses need special attention. Feeding horses isn't very complicated when you're armed with some basic information.

Feeding Basics

The goal of feeding horses should be to provide sufficient quality and quantity of calories and other nutritional needs for your horse's activities. However, quality can come at such expense that it's unaffordable. Luckily, the digestive tract and physiology of horses will allow owners to compensate for deficiencies in quality by feeding greater quantity. This approach has its limits. The best approach is to strike a balance between cost, quality and quantity.

Your Horse May Lack Variety

It's generally assumed that the nomadic life of wild horses (and their constant ability to forage on a variety of plants) accounted for their balanced diet. This is a reasonable assumption. It also follows that if the domestic horse is fed a limited diet (a diet with a small variety), then there may be some nutritional problems to address.

Expensive Diets Aren't Good Diets

Concerns of nutrition-related diseases seen in horses are secondary to concerns of dietary imbalance and overfeeding. Lack of feed is seldom a problem. Overfeeding, and supplement enthusiasm, create many nutritional problems: it is not unusual for owners to spend a great deal of money on supplements and forget that the basis of a good diet for healthy horses is roughage.

Hays and roughage generally come in four forms: legumes, grasses, cereal grain hays and residuals from food processing (e.g. sugar beet pulp).

Alfalfa Hay

Legumes include alfalfa and clovers. Alfalfa is by far the most commonly fed legume. Its high nutritional density per acre, and its relative ease of cultivation, account for its popularity. It may be less available in some humid climates in the United States because of difficulty in harvesting. Alfalfa often contains twice the protein, three times the calcium, and up to six times the amount of magnesium of grass. In general, good-quality alfalfa is all the diet most horses need. But alfalfa can be a troublesome forage for the pregnant mare's fetus or the growing foal. Copper, manganese and magnesium content, as well as calcium and phosphorous imbalances, can lead to skeletal diseases in these young horses. Imbalances can be overcome with appropriate supplementation to the pregnant mare's diet.

Judgments of quality shouldn't be made based on the external appearances of a bale of alfalfa hay. The outside can be yellow and have leaves while the inside is leafy and green.

Some insects found in alfalfa can cause a major problem for the horses that consume them inadvertently. Blister beetles are long, thin and brown or black striped insects. They are rare but are associated with serious consequences if the dead beetles are consumed (Blister beetles contain a potent irritant that can damage the stomach and urinary system.) Hundreds of beetles can sometimes be found in a single flake of hay.

Grass Hay

Grass hays can vary from mixes to nearly single species crops. Grass hay species include: timothy, blue, orchard, Bermuda, fescue and many other grasses. They tend to have more phosphorous relative to calcium and less protein content than alfalfa hay.

Cereal Grain Hay

Cereal grain hays include oat and wheat hays. They are more challenging to feed and harvest consistently. A few days difference in harvesting time can greatly affect the energy content of these hays. If the seed is lost, these hays become straws.

Other Roughages

Other sources of fiber and roughage can be used, like beet pulp and mint compost. These are often used in pelleted diets.

What Hay Is Best To Buy?

Crops that do well in Montana may not be productive in Georgia. For example, it doesn't make sense to try to find expensive and rare grass hay in southern California when alfalfa hay is far more readily available. Stick with hay common to your locale. This will let you maintain a constant feeding program in case you lose your source and need to switch to a different seller.

Forage is the foundation your horse's diet. Consider grain a supplement to balance the forage portion of the diet. It's wisest to provide good quality roughage and, if necessary, add enough grain to balance the ration to your horse's nutrient needs. In general, legume hays, such as alfalfa, are much better nutritionally. So, even though they may cost more, you won't need as much added grain in the ration as you would for an equal amount of grass hay.

On the other hand, many horses don't need any more nutrients than those supplied by good quality grass hay. In this case, paying more for legume hays would be a waste. In the western U.S., however, grass hays are often more expensive than alfalfa hays because more alfalfa is cultivated.

Hay Quality

Hay should be free of mold. It should be leafy with fine stems, as well as soft and pliable to the touch. Increased stem thickness often indicates older plants that have less digestible content. Color is least important. The outer portion of the bale should be bright green or yellow while the inside portions should be bright green. The hay should not be brown. A brown color often indicates heat damage from a high moisture content. Your nose is a good quality indicator. Hay should smell fresh and fragrant. If it doesn't it may be lacking essential vitamins, including Vitamin A and E.


Most mature pleasure horses doing light work need only the nutrients supplied by good quality grass or alfalfa hay. A good starting point is 1 1/2 percent of the horse's body weight divided into two or three meals daily. As an example, 5 pounds of hay 1 (flake) should be fed three times per day to a 1,000 pound horse. This percent can be decreased to 1 percent for second or third cutting alfalfa hay. Use this only as a guide. Some horses need more and others less. The tendency is to feed too much, except in the winter months when the energy demand is greater in cold climates.

It is a poor assumption that growing horses, lactating mares or pregnant mares need a much greater caloric intake. Only late term mares need greater amounts of grain, about 30 percent more. The lactating mare requires from 30 to 50 percent more calories, with the peak amount given during peak lactation (4 to 12 weeks after foaling). It is more important to feed according to the body condition of the mare. Under most circumstances, these horses need mineral supplementation more than calorie supplementation. More of these horses develop problems caused by overfeeding poorly balanced diets than by consuming insufficient calories. If you have questions about the quality of your horse's diet, you may have your forage tested for protein, fiber, energy, and mineral content. If you have a large load of hay, and a bunch of horses to feed with different demands, it's well worth it to know what their eating. Your veterinarian can guide you on the proper way to sample the hay for submission to a laboratory for forage analysis.