The Importance of Protein for Horses

Last Updated on October 29, 2020 by Allison Price

Brown Horse Eating Grass

Many horse owners are afraid of protein. And think it makes their horses crazy. In young horses, some believe it causes laminitis and growth problems. Or even contributes to kidney damage. But in fact, protein does not cause any of these problems. As a matter of fact, 15 percent of your horse ‘s body mass contains protein. This can be found in the muscles, hair, and skin, and hooves. Unfortunately, protein is somewhat misunderstood. Which is a real problem as it is important.

It is necessary to understand how protein is being digested and consumed. Also, the various dietary sources of protein that are available to the horse. As well as the protein and amino acid needed for horses of different ages and physiological states. These are all important to provide enough dietary protein. To give you a clearer understanding of the protein’s role in the diet of your horse, keep scrolling!

My horse needs protein because…

These are the main protein functions in the body of your horse:

  • Provides structure
  • Transports nutrients in the blood stream
  • Transports nutrients through cell membranes
  • Controls metabolic function as a part of the immune system
  • Serves as a buffer to reduce body pH fluctuations

Protein helps to repair and grow tissue. Thus, increasing the amount of protein needed in… developing, lactating, pregnant or heavy exercising horses.

Digestion of Protein

Proteins are primarily made up of amino acids. Even though there are 21 different amino acids needed for protein synthesis… the body’s tissues can make some of them. Amino acids that you need to give in the diet are essential amino acids. Also, amino acids produced by the animal by its own metabolic pathways… are referred to as dispensable amino acids.

They need to be digested first into the individual amino acids. So that your horse will be able to use dietary protein in his body. Protein digestion starts in the stomach. Then to the small intestine, and then results in free amino acids as the final product. Then, these will be available for absorption to the blood stream. And used in the body of your horse for different functions. The rates of absorption of each amino acid depend heavily on the source of the protein.

How much protein should I give my horse need?

We must understand first before we can address that query. The rate of absorption of each amino acid… as discussed previously in your horse. And thus, their performance depends on the source of protein your horse is taking. This only suggests that you must not only look for the amount of protein in the diet of your horse. But also, for the quality of protein.

You can also determine the content of the dietary protein. It is by the quantity and proportion of the essential amino acids it contains. Lysine amino acids are most likely what they add. To improve the protein content in commercial horse feed. Threonine and methionine are also added along with Lysine.

There is no definite sign for detecting a dietary protein deficiency. But noticeable withers and also hip bones and lack of muscle mass on the back and rump of your horse. They may mean that together with an exercise regime… a quality protein is necessary.

Other signs of protein deficiency:

  • Non-thriftiness
  • Weight loss
  • Depressed feeding intake
  • Reduced consistency of hoof as well as hair coat

If there is lacking in an important amino acid especially in growing horses… you can see this in the lower rates or value of average gain daily. Other studies also reported that decreased milk production, decreased foal growth rates… and increased loss of weight in mares… when there is inadequate dietary protein during lactation. Of all the horses, growing horses as well as lactating mares need high rate of protein in their diet.

We look at a daily protein allowance of 700 g versus 1500 g. For lactating mares when we use a 500 kg horse in light work. This is more than twice the allowance. Also, athletic horses who do not consume enough necessary amino acids… to sustain their increased muscle mass or replace the loss of nitrogen in sweat will start to… deplete the pool of plasma amino acids or lose muscle mass. And this can lead to increased excretion of nitrogen.

Sources of Protein

Not all sources of protein are the same. Some of which are of better quality than others. You can determine a dietary protein’s quality. It is by the quantity and proportion of essential amino acids it contains. From roughage to grains, your horse eats many ingredients. Each have varying amounts of protein quantity and quality.

High-quality protein

Legumes are sources of high-quality protein. Like soybeans, lupins, tick beans, and seed meals from sunflower and canola. But I must point out that soybean meal’s amino acid profile is superior to most other. About 44-48 percent protein-content seeds and beans. HYGAIN ® GROTORQUE ® is a textured feed which gives protein levels of high quality.

Moderate – Low quality protein

Mix cereal grains into horse diets for energy. But they do also include protein and certain amino acids. The grains of cereals do not contain protein of high quality. So, grain by-products, although they may be high in crude protein. They often contain moderate or low-quality protein.

Consider the amino acid content of by-product feeds when mixing into horse feed. Especially if their inclusion reduces the use of higher-quality protein ingredients.


Last but not the least, roughage is an important part of the diet of your horse. And it can be an excellent source of protein and amino acids. The down side is that in their protein and amino acid content, roughages can differ. Legume forages can usually reach a 14 percent protein concentration. This is greater than most grass hays. Because of its high lysine levels. Lucerne, for example, is a high-quality protein source.

Two Brown Horses Feeding On Grass

Protein Excesses and Deficiencies

Horses receiving insufficient amount of protein in their diet… can experience a variety of adverse effects. This includes decreased growth and growth in youngsters. As well as decreased appetite, loss of body tissue, slow growth of the hoof, energy deficiency. And weak adult hair coat with decreased shedding. Muscle deterioration may also be noticeable. Especially in the large muscle groups in the hindquarters. And some horses would begin eating manure.

A stressed, protein-deficient horse’s decreased food intake can be a vicious cycle. Because it makes it impossible to cure the problem with a correct diet. But an adult horse’s protein requirements are low enough. And that true protein deficiencies are very rare. Most of the time, they occur only if a horse for a prolonged period of time is on very bad pasture. Or hay with no other supplementary feed.

Many of the symptoms of protein deficiency happening adult horses can turn around. It can happen in less than a week with a corrected diet. But the harm done to a young and growing horse may be more serious.

Having more than enough of protein in the diet particularly in mature horses… that are being taken care of by owners who do not have enough understanding. Especially on the importance of protein in giving their horses the energy. This is more common and dangerous. 

Here is what happens:

The protein that the horse’s system does not use immediately is broken down. This is to release the atoms of nitrogen. And those atoms of nitrogen are being wrapped together as molecules of ammonia and urea.

In the urine, ammonia and urea are excreted, resulting in increased water intake. Also, increased urination, and a strong smell of ammonia in the stall. They must be removed out of the blood before ammonia and urea is taken out in the urine. Because they can tax the kidneys over time. It is possible that this might contribute to reduced renal function. Indicating that liver and kidney failure can get worse. By unfiltered urea and ammonia throughout the bloodstream.

Another potential consequence of a high-protein diet is less in athletic efficiency. Also, there is some proof that calcium absorption can be interfered with by excess protein. But experts disagree about how much harm a high-protein diet can do. And how long before the results (if any) are plain, a horse must take such a diet.

In growing horses… there is stronger proof for the adverse impact of excess protein. Weanlings and yearlings that are being fed a diet 25 percent higher in protein than average in one study… experienced slower growth rates. And a higher incidence of bone and joint developmental problems.

How much is enough?

So, what is the right protein level for your horse? The response is changing all the time with continuous testing. But here are some of the general guidelines.

How much crude protein required in the diet is dependent on the individual horse’s needs. Also, the protein’s digestibility, and the amount of diet eaten. Some values that are recommended for horses in various stages of life… are in the accompanying table. In general, a value of 0.60 g of digestible protein/kilogram of body weight each day… is enough for most adult horses.

Broodmares do not need supplementary protein levels… in the first eight months of gestation. But their protein needs to increase in their last trimester. When the time the fetus develops 60-65 percent of it. Higher levels of protein are also necessary for lactation or milk production. The protein content of mare’s milk is highest after foaling. And decreases as the lactation period continues.

Most mares produce relatively small amounts after three months of milk production. And foals are beginning to eat more solid food. And a return to their normal protein levels is typically acceptable.

Some researchers suggest that a higher level of dietary protein… may also support breeding stallions. This is, however, cut back once the breeding is over for the year, may also support breeding stallions.

Hard exercise like racing, three-day activities, or endurance racing… increases the dietary protein need of adult horses. This is to encourage increased muscle growth and mass. And replace nitrogen lost in sweating. But the increase is very slight, just 1% to 2%.

Feeds that give the best protein

What feeds provide the best protein? The best amino acid profile and the highest levels of lysine are from animal sources. Like milk and egg protein, and also fish and meat meals. Milk protein is often used as the primary source of protein for foal feed. But it is rarely contained in feed for mature animals. Because it is very costly. And because adult horses are much less sensitive to variations in protein quality.

Among the plant sources, the next best thing is soybean and canola meal. These are the only two plant protein products… containing enough quantities of lysine and methionine. Other traditional sources of protein… like linseed and cottonseed meal, have low amino acid profiles. And are usually supplemented with the feed manufacturer’s added amino acids.

Grains can contain between 8 percent to 20 percent. Like oats, maize, and barley. But they are of low quality. That is why most feed companies… add a higher-quality protein supplement to their healthy feeds. These include sweet feeds, pellets, and other pre-mixed rations.

If the farmers have done their job, the feed should contain at least 0.65 percent lysine on a dry matter basis. If this level is not present, there is a need for more feed. Especially with young, growing horses to get the same results.

Like anything else, it is a matter of reading the feed tags, doing your homework. And exercising some moderation. To provide the right amount of protein to your horse! Although protein is an integral part of the diet of your horse… it needs to be put into context as just one part of the nutritional framework of a functioning whole.


Protein in the diet of your horse, is a very essential nutrient. It was from the Greek word “proteose” which means “primary importance”. Note, your horse’s protein need is based on his physiological state and his level of exercise. To prevent muscle weakness and poor hoof and coat quality… make sure your horse receives appropriate amounts of quality protein.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!