Equine Nutrition

We now have a greater understanding of nutritionally related diseases and have much improved our ability to help horses perform at their best.

The most important thing that you can take from this article is the emphasis that horses absolutely must be fed as individuals!!!! There are digestive and metabolic differences among horses that make some hard vs. easy keepers. Other considerations that must be taken into account are variations in production and performance. Some horses really have to work hard for a living, and others lead the simple life. The health status of the horse also plays a big role in the level of nutrition that it requires. There are different nutrient availabilities in the same feed types…aka not all grass hays have 10% crude protein. It varies. The previous nutritional status of a horse is also a very important consideration. Last but not least, not all horses even in Central Oregon are exposed to the same climate and environment. These variables all have to be taken into consideration when talking about nutrition. What works for one, may not work for others.

There have been significant changes in equine nutrition, and they continue to research and study the most efficient methods of feeding our horses. The most recent and newest information changes continually.


Horse owners around the world regularly put water on the backburner in terms of value.  We can- not overemphasize the importance of a clean available water source for your horses at all times. If you want to increase the amount of water that your horse drinks during the winter months, provide warm water as the sole source of water. Horses, if given the choice between warm and cold water, will drink the cold water. But, they will drink far less of the cold water than they do the warm. Confined horses drink within a few minutes after eating grain and an hour on average after given hay. Exercise decreases the blood flow to your horse’s intestines by 75%. Periodic rests of at least one hour with access to water will significantly decrease the risk of problems associated with this. The risk of colic or founder when hot horses intake cold water during rest and do not continue exercising after is quite high. Resolution of this is to allow small amounts of warm water, and always cool down!! Added fat to the diet of performance horses increases water retention. This water is then available for sweat and heat dissipation.


High quality forage (pasture or hay) is THE most important source of energy and nutrients for horses. It is repeated over and over again in the literature. They can ingest 2-3% of their body weight daily, depending on the quality of the forage.

Fat is now becoming a big player in terms of horse nutrition. Studies have shown almost 100% absorption of fat with no negative effect on fiber digestion. Vegetable sources seem to be the most palatable. It is important to condition horses slow and gradual three weeks prior to intense exercise.

Protein must be provided to exercising horses to provide nitrogen and amino acids needed for muscle development, muscle repair, and for replacement of sweat losses. Too much protein will have negative effects on performance, though. There was no difference seen in quiet adult horses in a study to determine the effects of feeding 7.5% vs 14.5% protein. It all depends on what the horse is doing.

Vitamins and Minerals

A complete loose mineral mix should be available to your horses at all times. It should be formulated specially for your area. This is a big area in terms of horse research. They are continuing to determine the importance of certain vitamins and minerals in problems that we see in the horse population. Copper deficiency in late gestation mares has been implicated in certain developmental orthopedic diseases in foals. Selenium and Vitamin E play a huge role in decreasing exercise-induced oxidative stress and decrease tissue damage. They are also important as antioxidants and with the immune system. Oral forms of Vitamin E have been shown to work better than injectable. Calcium, magnesium, and phosphorous are three very important minerals for maintaining healthy bone structure in horses. Older horses have a decreased ability to respond to exercise after idleness, which increases their risk of injury. Vitamin A deficiency has been implicated in increased chances of mares retaining their placenta and having foals with contracted tendons. Dry lot mares need supplementation with the retinyl palmitate form of Vit A.


Mares begin to have large changes in their nutritional needs around the 9th month of gestation. During the last trimester, requirements increase 11%, 13%, and 20% per month. During the first three months of lactation, mares can produce milk equivalent to 3% of their body weight daily!!!!! Preparing mares for weaning with fat and fiber will decrease problems associated with the stress of weaning. Mares with adequate selenium and vitamin E concentrations may have foals with improved passive transfer and initial immunity. Mares should be at a moderate weight prior to foaling. Mares kept in a fat condition in fall and winter, are better prepared for breeding than thin mares.


A study showed that there were no significant effects on growth by weaning a colt at 4.5 versus 6 months of age. It is very important to follow your colt’s growth closely. There is an increased risk of developmental orthopedic disease in large, rapidly growing foals. The same principles apply to these horses, as older horses. They need good quality water, forage, protein, vitamin, and mineral. Amount should be tailored to each individual’s needs.


As I mentioned earlier, these horses require more overall nutrition, because they are using what you give them in entirely different ways. The thing to remember is that it can potentially be detrimental to just add energy to your horse’s diet in the form of concentrates=sweet feed. Balanced forage, protein, fat, and concentrate will return the greatest performance level. One area of research that I find interesting is that of the benefits of electrolytes. Hypertonic electrolytes given to horses just before and during exercise produces greater health benefits than not. These horses drink twice the water of horses not receiving them. You must supply free access to water!


A geriatric horse is any horse older than 20. These horses have special needs. Body weight, body condition scores, dentistry, disease resistance, and arthritis are some of the major considerations for these horses and maintaining their proper level of nutrition. We use our horses longer now than we did in the past. We keep them healthier longer. In return, we are finding out a lot about their nutritional needs. Pelleted feeds are great vs sweet feeds, as long as the horse doesn’t have a history of chronic choke. At Auburn University, they poled the number of older horses that they treated for colic, and impaction colic accounted for 88% of the total population. Their teeth, or lack thereof played a huge role in this figure. Older horses that were stalled >50% of the time, were suggested to have more problems. Smaller, more frequent meals may also help. The older horse’s immune system may be depressed as well, setting them up for problems. If a horse is incredibly arthritic, or suffers from any chronic orthopedic problem, it will have a harder time getting to water, feed, and free choice mineral. If all of your horses run together, take care to separate out the older ones if they are slow to feed.

Feed Times and Restrictions

Feeding only small amounts of forage prior to heavy exercise resulted in no adverse effects on performance. High amounts of concentrates fed prior to exercise can result in higher levels of damaging substances within muscles and the general system. Fat supplementation increases the horse’s ability to use fat at rest and with exercise.

Nutritional Related Disease

Equine Rhabdomyolysis Syndrome

Affects the muscles of horses of nearly any age, breed, or gender. This is commonly known as tying-up. There is no single diet change that stops recurrent exertional rhabdomyolysis. You can help reduce the frequency and severity of attacks. Replacing most of the grain in the diet with a high-fat, high-fiber, low-starch diet keeps these horses muscle breakdown enzymes at lower levels.

Polysaccharide Storage Myopathy

An abnormal accumulation of sugars in skeletal muscle. These horses must stay on a low sugar diet. Good quality hay is often enough to supply the needed calories and additional fat has been proven beneficial. Two pounds of rice bran or one cup of vegetable oil plus 600-1000 IU/day of vitamin E has been found to reduce muscle glycogen