11 Signs of Lysine Deficiency in Horses & How to Treat Them

According to veterinary science, there are around 20 different amino acids a horse needs. These 20 amino acids must be combined to make a protein. Generally, amino acids are such components that work as an auxiliary to build blocks of protein.

Signs of Lysine Deficiency in Horses

Nine amino acids out of twenty can’t be made by the horse’s body and need to be obtained from food. And the nines are known as essential amino acids. Like the nine, lysine is also an essential amino acid that a horse’s body can’t produce.

It’s required for proper growth and development in horses. It is a key component of many proteins and is necessary for the production of enzymes, hormones, and other important biological molecules. Also, it’s involved in the assimilation of calcium and the foundation of collagen.

A lysine deficiency in horses can lead to a number of problems, including stunted growth, poor appetite, and muscle wasting. While lysine is found in many common feeds, it can be difficult for horses to absorb enough of it from their diet.

Signs of Lysine Deficiency – A Guide to Identifying The Lack of Amino Acid in Horses

The signs of lysine deficiency can be difficult to spot, but knowing what to look for can help you identify the problem. There are a number of signs that can indicate a lysine deficiency in horses, and it is important to be aware of these so that the problem can be addressed early. These are:

Slow Growth

Lysine deficiency is often seen in young horses. It plays an important role in the production of enzymes, hormones, proteins, and the absorption of calcium needed for tissue repair and growth. A protein that helps keep bones and connective tissues strong. This is why the lack of lysine can lead to slow growth and development in horses.

Cracked, Brittle Hoof And Low Hoof Growth

Hoof growth is essential for the health of the horse. Cracked, brittle hooves are the most common sign of lysine deficiency in horses. Whether a horse is suffering from lysine deficiency can easily understand by observing the hooves. Collagen is a significant component of the hoof and lysin helps to produce it.

So the deficiency in lysine can therefore lead to slow hoof growth and other problems. If hoof growth becomes slow, it can lead to a number of problems. These include poor hoof quality, weakness, and difficulty walking.

We do a deep dive into hoof supplements that will improve your horse’s hoof growth.

Poor Coat Quality

Horses’ coats are made up of protein, and lysine is a key building block of protein. Without enough lysine, horses can develop a number of problems, including poor coat quality. The coat may become dull, dry, and brittle and may even start to fall out in patches.

Loss of Muscle Mass

One of the most common problems associated with lysine deficiency is the loss of muscle mass. Loss of muscle mass is a condition where the horse loses a significant amount of muscle mass. This can be a result of many different things, but one of the most probable reasons is lysine deficiency. As lysine is required for the synthesis of protein, without enough lysine, the horse’s body cannot properly build or repair muscle tissue.

Flagging Stamina

Lysine is required for the production of carnitine, which is responsible for transporting fatty acids into the mitochondria for energy production. A deficiency of lysine can therefore lead to a reduction in energy production and a fall down in stamina.

Like collagen production, lysine is also essential for tendons and ligaments. So, the laking of it leads to a decrease in tendon and ligament strength, which can lead to Flagging stamina in horses.

Low Milk Production in Lactating Mares

Lactating mares require more lysine than non-lactating mares, as it is necessary for milk production. A lysine deficiency can lead to low milk production as it’s involved in calcium absorption. Without enough lysine, the mare’s body cannot produce sufficient milk for her colt. This can be a serious problem for nursing foals, as they rely on their mother’s milk for nutrition.

Reproductive Disorders

Lysine deficiency is also a common cause of reproductive horse disease. A lack of lycine can lead to various reproductive disorders in horses, including infertility, miscarriage, and birth defects. The horse’s body cannot make enough protein to support reproduction.

However, it’s most important to ensure protein for the horse selected for conception. So, after being mature enough, if horses fail to reproduce, they may need a supplement of lysine, and the same for horses that have miscarriages several times. A veterinarian can suggest observing a particular situation.


When a horse is suffering from lethargy, it may appear tired, sluggish, or even sleepy. They may have difficulties breathing, and also may sweat profusely. In severe cases, a horse may collapse and be unable to get up. Fatigue or lethargy, whatever we say, can be caused by several factors, including illness, dehydration, and overexertion.

Anyway, horses who are deficient in lysine may experience lethargy too. In maximum time, their energy levels may be decreased, or they may show bad performance in activities such as racing and muscle weakness.

Loss of Appetite

Loss of appetite is a common problem in horses, and it can be originated from various factors like lysine deficiency. The body can’t produce enough of its protein when lysine is not available in adequate amounts.

On the other hand, protein is a must for the growth and repair of tissues, and it is also a significant source of energy for horses. Without adequate protein, horses become malnourished, and their body systems can begin to fail. This can cause loss of appetite and poor health in horses.


Nausea is an uneasiness of the abdomen that often precedes vomiting. Generally, it’s a common symptom in horses caused by inadequate lysine.


Another most common sign of a lysine deficiency is agitation. Without enough lysine, horses can develop several health problems, including poor muscle development, poor appetite, and stunted growth. So, they may become fidgety, anxious, and even hostile. Also, they may exhibit other neurological symptoms, such as head shaking or incoordination. If you suspect your horse is agitating, probably it’s suffering from a lysine deficiency.

How to Face Lysine Deficiency for Your Horse

How to Face Lysine Deficiency for Your Horse

While lysine deficiency is relatively rare in horses, it can occur if they are not getting enough of this essential nutrient in their diet.

If you think your horse may be deficient in lysine be deficient in lysine, you can do a few things to help. You should talk to your vet. Doctor’s can performig a blood test to check lysine levels and ensure no underlying cause.

If a lysine deficiency is diagnosed, you’ll need to adjust your horse’s diet to include more of this amino acid. This can be done by feeding them lysine-rich foods, such as legumes, soybeans, and alfalfa, or by giving them a lysine supplement. Feed the supplement as the veterinary prescribes or follow the instructions.

With proper treatment, most horses will fully recover from a lysine deficiency. However, it’s important to catch and treat the condition early to avoid any lasting effects on your horse’s health.


There are a few potential side effects of using lysine supplements with horses, including:

Diarrhea: Some horses may experience loose stools or diarrhea when first starting on lysine supplements. This is usually not a cause for concern and will resolve on its own, but it is something to be aware of.

Gastric ulcers: There is some evidence that lysine may help to heal ulcers in the stomach and intestine. However, it is also possible that lysine could aggravate existing ulcers or create new ones. If your horse has a history of gastric ulcers, it is best to talk to your veterinarian before starting them on a lysine supplement.

Allergic reactions: A few horses may be allergic to lysine and experience itching, hives, or swelling of the face, lips, or tongue.

If you notice such indications, stop giving your horse the supplement and call your veterinarian.

People Also Asked

#1. Can lysine ever be given in excess to horses?

Too much lysine means too much protein intake. Horses need more water to clear the excess protein and sometimes they can suffer from dehydration for the lack of water. The urination also increases with acute smelling because ammonia and urea pass through the urine. Besides, it can put a strain on the kidneys and liver too.

#2. How much lysine must a horse consume per day?

The quantity of lysine that a horse requiered depends on their physical condition, activity, and, age. According to NRC a horse of average weighted mature and usual activity should take 23 grams; horses with intense activity should take 46 grams. Reproducing horses and growing horses also need more than 46 grams of lysin.

#3. Can a high protein diet lead to laminitis?

Yes, a high protein diet can lead to laminitis because it can cause an increase in the level of insulin in the blood. Insulin is a kind of hormone that plays a role to modulate blood sugar levels.

#4. What amino acid should a growing horse’s diet be limited to first?

A growing horse’s diet should be limited to lysine first. It’s an essential amino acid for horses, meaning that they cannot synthesize it and must obtain it from their diet. It is important for proper growth and development, and limiting the diet to lysine first ensures that the horse gets enough of this essential nutrient.

#5. What is an excellent lysine source for horses?

Some excellent lysine sources for horses include soybean meal, sunflower meal, canola meal, flaxseed meal, cottonseed meal. alfalfa, and spirulina.

Parting Thoughts

You may find all the symptoms of lysine deficiency, but this article doesn’t recommend deciding whether you feed lysine supplements or not. No problem if you give lysine-rich food but in the case of supplement consumption, only a veterinarian’s judgment is acceptable.

Therefore, always try to follow a well-balanced, nutritious diet to overcome any kind of disease easily. Ultimately, an overall good diet ensures the equine’s good health. Wish your horse’s good health!

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