Horse Nutrition and Feeding

First, I am going to go through some horse nutrition basics and then I’ll talk specifics related to the endurance horse.

Basic Horse Nutrition Facts

When it comes to feeding horses, it can seem overwhelming and confusing with all the options available of feed types let alone supplements. It comes down to truly understanding what is in the bag of feed you have chosen and how it is utilized by your horse, and then it is much easier to manage our individual’s horse’s needs.

Four main factors to note with each individual horse:

  1. Age
  2. Breed/body type
  3. Living space (size and type)
  4. Exercise/use

Below I am going to discuss the key elements and basic principals concerning a horse’s diet as I think it is beneficial knowledge to keep in mind.

Horses get energy for metabolism through dietary carbohydrates, fats and proteins. Pregnant mares, lactating mares, growing horses, and performance horses require the highest amount of energy.


Proteins are chains of amino acids which are needed to build and repair muscle and body tissue and, as mentioned above, are metabolized to provide energy. One important fact to note is that there is crude protein and digestible protein. Crude protein is the amount of protein given on the feed label. Digestible protein is the amount of protein the horse can actually use. Protein deficiency will depress the horse’s metabolic activities, causing the horse to become lethargic, exhibit a loss of endurance, and he may become anemic. Protein is a must for the young, growing horse, but as the horse reaches adulthood, high protein diets are inefficient in the production of energy because protein metabolism produces much more heat than other forms (carbohydrates and fats).

Some feed labels will provide a minimum feed rating, meaning that in order to receive the amount of nutrients required in that feed, one must feed a minimum amount per day. If you do not feed the minimum (in such cases where your horse does not require the amount of carbs he would receive if given the minimum requirement), you can supplement with a diet balancer to ensure the horse is receiving adequate amino acids. This simply ensures the horse is receiving the adequate level of nutrients without necessarily increasing the nonfiber carbohydrate level (see carbohydrates below). Not all feed labels provide this system but I would not hesitate to talk with your feed store to obtain more information on your feed of choice.

Carbohydrates and Fiber

Carbohydrates are simple sugars and are classified as either fiber or nonfiber carbohydrates. Nonfiber carbs are the major source of energy and are the monosaccharide and disaccharide sugars. These nonfiber carbs are converted to glycogen and stored in the liver and muscles when energy demands are low. Fiber carbs are poorly digestible and are low in energy. Fiber carbs are important for gut motility.

Essential Fatty Acids

EFAs are an important part of the horse’s diet and are necessary fats that can only be obtained through diet. EFAs play an important role on many levels including organ support as well as cellular function and repair. In addition, these fats provide extra energy without extra carbs. The two essential fatty acid groups are Omega 3 and Omega 6. Omega 9 is considered a non-essential fatty acid as it is manufactured by the horse. The correct ratio of Omega 3 and 6 is 1:5 and it is important that this is maintained to avoid unnecessary inflammatory responses such as arthritis, laminitis and skin disorders.


Minerals are a necessary part of the horse’s diet and play an important role. The minerals of main concern are calcium, phosphorus, salt and in some areas selenium. Copper and zinc are essential for growth. However, it is an important fact to keep in mind that you can have mineral deficiency or toxicity and one must be careful when supplementing minerals, especially phosphorus and selenium. I like to offer a 12:12 mineral block free choice in the pasture to allow the horse to choose when it is needed. Sometimes the mineral block is rapidly consumed (especially the first time it is offered), and at other times the block has lasted six months or greater.

Salt provides sodium and chloride. The lack of salt results in decreased appetite and weight loss and salt is necessary for cell function. It is important to note that when salt is either supplemented or offered free choice, water must be available at all times to prevent toxicity. Salt toxicity only occurs when salt ingestion is high without adequate water consumption. I personally like to offer free choice salt blocks and I give an electrolyte when needed according to weather changes and/or exercise demands.

Calcium and phosphorus are an extremely important part of the horse’s diet and it is very important not to offset this ratio, which should be approximately 1.2:1, meaning there should be at least as much calcium in the diet as phosphorus. More phosphorus than calcium can result in bone demineralization. Calcium and phosphorus are very important to the young growing horse as well as mares in the late months of pregnancy and lactating mares, and these horses should be given a calcium supplement to meet their needs. As long as the amount of calcium is equal or greater than the amount of phosphorus, there should be no worry for deficiency. Horses can often tolerate more calcium then they require, but excess phosphorus can cause calcium deficiency. Bran is an example of a feed that is high in phosphorus and, if fed, a calcium supplement such as calcium carbonate (limestone) should be given as well. Beet pulp on the other hand is high in calcium and is a great fiber/roughage source.

Potassium is an important mineral and is usually of adequate amount in most feeds. Horses that may be deficient in potassium are those that are fed a high grain diet and low in forage such as a horse under heavy exercise demands. Potassium is also lost through sweat and, therefore, these horses may have a greater need for potassium. Signs of potassium deficiency include muscle weakness, lethargy and diminished water/food intake. This may be most commonly seen in the endurance horse or a horse working heavily in hot, humid weather and it can be avoided by giving a potassium salt supplement such as “lite salt,” which provides sodium chloride and potassium chloride.

Trace minerals. Most feed stuffs provide an adequate amount of trace minerals. Deficiencies are rare and problems usually occur when trace minerals are excessively digested. Selenium and vitamin E work together as an antioxidant. Some areas of the United States are deficient in selenium; however, it is important to note that selenium toxicity is much more common than deficiency so this must be approached with great care. Iodine plays an important role in synthesis of the thyroid hormone. An iodine deficiency causes hypothyroidism whereas an iodine excess causes hyperthyroidism. Copper and zinc play an important role in bone formation and metabolism in the growing horse. Iron plays a role in the transportation of oxygen in red blood cells. Horses naturally increase their red blood cell production in times of stress/excitement or exercise demands; thus, iron supplementation is a rare need. Consumption of more than 2 grams of iron a day is considered toxic to the mature horse.


It is interesting to know that most vitamins are synthesized by bacteria in the horse’s hindgut and the only vitamins that need to be supplied by the diet are vitamins A and E. Vitamin A is essential for the eyes, bones, and cell growth. Vitamin A deficiency is seen in horses that have little or no fresh grass in their diet and is an important vitamin for breeding horses. A vitamin A deficiency can cause respiratory and reproductive tract infections and can lead to eye problems such as night blindness and excessive tearing. Excessive vitamin A causes brittle bones and skin sloughing. Horses consume vitamin A by grazing on spring and early summer grass which contains carotene, which then converts to vitamin A. A horse can store enough vitamin A in their liver to last three to six months. A vitamin A supplement can be given when poor/old hay or poor quality, non-green pasture only is available for an extended period of time. If you think you may need to give a vitamin A supplement, I would recommend talking with your veterinarian first.

Vitamin E is an antioxidant that is essential to muscle function and plays an important role in the horse’s immune system along with selenium. Most green forage provides an adequate amount of vitamin E, but if you mainly feed cured hay and/or pelleted feed (both of which are typically low in vitamin E), you may want to add a vitamin E supplement. Adult horses require 500 IU/day.

Grain/Feed Types

Oats are high in fiber and low in energy content.

Corn is high in energy content, twice as much energy as an equal volume of oats. Corn is high in vitamin A.

Wheat bran is low in energy content. Wheat bran is high in phosphorus and low in calcium. If wheat bran is used, water should be added and a mash made as it soaks up a lot of water and could cause an impaction if fed dry. A calcium supplement such as calcium carbonate (limestone) should be given if wheat bran is a routine part of your horse’s diet. I like to use a little wheat bran on exceptionally cold winter days/nights with warm water to add a little bulk to the evening feed and keep gut motility moving.

Beet pulp is high in fiber content and high in calcium. It comes in pelleted form or shredded. The pelleted form should be soaked in water for 12 hours prior to feeding (be sure to soak this in a temperature controlled environment as high temperatures can cause excess gas and possibly gas colic when digested by the horse). The shredded beet pulp can be fed immediately to the horse upon the addition of water. There seems to be a bit of a controversy over whether it is safe to feed dry shredded beet pulp, some saying that the horse is at risk for choking if fed dry. However, many feeds now are adding beet pulp to their ingredients, which is then fed dry but is also ground up in a finer form. I personally am a beet pulp advocate and I do add water to the grain/beet pulp mixture just before feeding.

Sweet feed versus dry mix feed. Sweet feed contains molasses, which is highly palatable and adds extra calories. A dry mix is basically sweet feed without the molasses or low molasses content.

Pelleted feed is ground up grain and roughage that is pressed together to form a pellet and is usually considered a complete feed.

Feed and the Endurance Horse

So how does all this relate to the endurance horse? The main things to consider about your endurance horse are: age and workload.

Many feeds that are advertised as “endurance feed” are high in fat (10-12%) and low in protein (typically as low as 10%). As a consumer, you need to consider the age and workload of your horse and know the fat source in your feed.

Protein and the endurance horse

For the still growing 4-year-old, I do believe they still need a higher protein, 12-14%, simply because they are still developing. However, once your horse is ready to go into 50-milers, the protein is something to really look at. As stated above, the horse produces energy through metabolism of protein, carbohydrates and fat. However, this metabolism produces a lot of heat that the horse must then dissipate. Protein metabolism produces far greater heat than carbohydrates and fat; therefore, protein is an inefficient source for energy in the endurance horse.

Fat and the Endurance Horse

Fat is a very important component to your feed as the endurance horse needs a healthy storage of long-term energy, something they can pull resources from when needed. You don’t want the high-low energy that sugar produces, but rather sustainable energy. For this reason, avoiding high starch feeds (such as corn) is wise. Fat provides energy for aerobic activity but not anaerobic work, meaning that the horse will pull all their energy requirements from fat during aerobic activity, saving their stored muscle glycogen for anaerobic activity. This is important because muscle glycogen produces lactic acid during anaerobic activity and lactic acid is not produced through the breakdown of fat during aerobic activity; thus, extending your horse’s endurance and helps delay muscle fatigue.

If your feed of choice does not have a sufficient amount of fat to keep up with your horse’s demands, you can supplement with a fat supplement. It is wise to increase your fat content before increasing the daily ration of grain. Besides just a healthy shine, fat is a good source of Omega 3 and 6 essential fatty acids (EFTs), which provide many great benefits, including cell health and better absorption of fat-soluble vitamins (E, A and D). It is important to know your fat source not only in your feed but also when choosing your fat supplement as not all fat sources are equal in their Omega content.

It is also important to know there is a Omega 3:6 ratio that is as important as the calcium:phosphorus ratio and should be kept in balance. The ratio should be 1:5 (Omega 3 to 6). There are two basic EFT families, Omega 3 and Omega 6. Omega 3 is made from alpha linolenic acid and Omega 6 is made from linoleic acid; the horse’s body uses both of these to produce other EFTs. The correct balance/ratio of the EFTs is essential to maximizing immune, antioxidant and anti-inflammatory responses (reducing muscle damage and fatigue, improving cellular repair and recovery, and maintaining cell function for efficient oxygen and electrolyte and lactic acid secretion and excretion).

Omega 9 is not an essential fatty acid as this is naturally produced by the horse. Stearic acid and oleic acid are examples of Omega 9 fatty acids.

Rice bran is very high in phosphorus, something any owner should avoid unless supplementing with extra calcium to make up for this so as not to upset the calcium/phosphorus ratio. Most commercially prepared feeds that use rice bran as a fat source will compensate with extra calcium somewhere; just be aware of this fact and check your labels. Or, for the owner that feeds straight rice bran, this high phosphorus content can be offset by feeding alfalfa, which is high in calcium. Alfalfa is also a great natural GI “buffer.” As stated above, too much phosphorus in comparison to calcium inhibits calcium absorption and causes bone demineralization.

Beet pulp is a great roughage source to add to your horse’s daily ration. Because it is so high in fiber, it is considered a very safe feed to use. Some people choose to only use this at endurance rides, but I use it daily on every horse in endurance or training for endurance. It is also a good feed to use on that hard-keeper as it helps them maintain weight better and is a better choice than increasing grain intake. I like to use the shredded beet pulp as it requires less soaking than the pelleted form, which can require 12 hours of soaking prior to feeding.

If I have a hard keeper, I add a fat supplement and/or beet pulp before increasing the amount of grain. The amount in pounds I feed depends on the horse’s body condition, metabolism, and workload. Every horse is different and must be evaluated based on their personal needs. See my Personalized Training Program if you would like me to set up a horse nutrition program for you.

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