Do you know your horse's protein requirement?

Do you know your horse's protein requirement?

7 reasons to supplement lysine, methionine, and threonine

A horse’s body composition is 65% water and 20% proteins. Proteins are needed in all of the body’s cells, but especially for building and strengthening the horse’s musculature. There are 20 different amino acids, and the horse’s body cannot produce ten of them itself (the so-called essential amino acids). For that reason, the horse must get them from its daily diet. This is why, in protein feeding, it is important to pay attention not only to quantity but also to quality.

Because a horse cannot store excess amino acids in its body, and because amino acids are required in certain ratios to form specific proteins, the quality of protein obtained from feed—i.e., the amino acid profile—matters. The horse must receive sufficient amino acids daily, and in the correct ratios, in order to build proteins. If any amino acid is available in too small an amount (a so-called limiting amino acid), it limits the body’s protein synthesis even if other necessary amino acids are available in sufficient quantities. Feeding excessive amounts of individual amino acids does not benefit the horse, and you cannot compensate for a missing amino acid by overfeeding another one.

In horse feeding, the most important essential amino acids are lysine, methionine, and threonine. These are essential amino acids that the horse must obtain from feed and cannot synthesise itself. The most common limiting amino acid is lysine, and often methionine and threonine as well, because hay and oats contain relatively little of them. Plants are the horse’s most important protein sources, because they contain, to some extent, all of the amino acids the horse needs. Legumes, such as alfalfa and soybeans, typically contain the most protein and also provide more lysine, threonine, and methionine. Chia seeds and hemp seeds also contain lysine, methionine, and threonine.

The right kind of protein supplementation supports overall wellbeing

If the horse does not get enough protein from its feeds, it cannot maintain or develop muscle mass. In addition, deficiency may show up as poor hoof and coat quality, constant tiredness, underperformance, slow recovery from illness, and loss of muscle mass. Poor hooves can also indicate a lack of appropriate protein. In foals, deficiency may be visible especially as slowed growth. The severity of symptoms depends on how long the deficiency has continued, how severe the deficiency is, and whether there are also deficiencies or imbalances in other nutrients. Adequate and sufficiently versatile protein supplementation supports the horse’s performance capacity and overall wellbeing.

7 reasons to supplement lysine, methionine, and threonine sufficiently

  1. Better topline and muscle function: Adult horses that have received lysine and threonine as supplements have better muscle mass regardless of age. In one study, horses that received supplemental lysine and methionine had more muscle mass and less body fat than a control group regardless of body weight. In the same study, horses in light work that were given supplemental lysine and threonine had lower 3-methylhistidine levels, indicating less muscle damage. According to studies, the requirement for these amino acids—especially threonine—increases with training. Threonine enhances the development and maintenance of muscle mass.

  2. Antioxidant protection: The amino acid methionine can be converted in the body into another amino acid called cysteine. Along with glutamine and glycine, cysteine is needed for the production of glutathione, one of the body’s most powerful antioxidants. Sufficient antioxidant protection can help tissues recover faster from exercise. In addition, glutathione is believed to slow the ageing process and may help prevent numerous diseases.

  3. Gut health: The amino acid threonine is crucial for the synthesis of mucin proteins in the intestines. These proteins create a protective barrier between the acidic environment inside the gut and the tissues of the stomach and intestines. Horses with digestive problems may benefit from additional threonine, which supports a healthy intestinal lining, reduces the risk of ulcers, and improves nutrient absorption.
  4. Joint health: Threonine is converted into other amino acids, glycine and serine, which are important for healthy connective tissue. Glycine and serine are needed to produce collagen and elastin proteins, which are abundant in connective tissues such as ligaments and tendons. Elastin is a protein that increases tissue elasticity. Threonine and lysine are also directly integrated into the structure of collagen, especially into cross-links between chains that enable collagen chains to connect with one another. Lysine also inhibits the activity of certain enzymes (MMPs) that increases resistance to collagen breakdown.
  5. Hoof health: Keratin is a protein that is abundant in hooves. It contains high levels of an amino acid called cysteine. Although cysteine itself is not an essential amino acid, a large portion of it comes from the conversion of methionine into cysteine. If methionine is limited, less cysteine is available for making keratin in hoof tissues. Horses whose hooves crack or crumble may need increased methionine in their diet. Other nutrients, such as zinc, copper, and biotin, are also important for supporting hoof quality. A balanced diet with sufficient vitamins, minerals, and amino acids is the best way to support hoof health in horses.
  6. Coat quality: Keratin is also abundant in hair follicles. A sufficient methionine level in the diet can support a healthy coat by increasing the availability of cysteine. Sulphur bonds between cysteine residues in keratin create a rigid structure for this protein. Horses with coarse, brittle hair may particularly benefit from methionine added to the diet.
  7. Immune function: Amino acids are needed to produce many antibodies and signalling molecules, which are required to fight infections caused by viruses and bacteria. In other animals, lysine has been shown to help reduce the impact of herpesvirus infections. Lysine competes with the amino acid arginine for absorption and metabolism. Herpesviruses require arginine to function properly and replicate. Equine herpesviruses (EHV-1 and EHV-4) cause respiratory disease in horses known as rhinopneumonitis. They can also cause abortions in pregnant mares and impair neurological health. Although this has not been studied directly in horses, supplemental lysine may be one way to reduce symptom severity and minimise outbreaks, as has been reported in other species.

How much protein and individual amino acids does my 500 kg horse need?

Many factors affect a horse’s individual protein and amino acid requirements, such as age, the amount and intensity of exercise, physiological state including pregnancy and lactation, and general health status.

The diet of an adult horse should contain 8–10% protein. This corresponds to a need of about 630 grams of crude protein per day for a 500 kg horse. The minimum amount of lysine is 18 grams, but the optimal intake for a 500 kg horse is 27 grams per day. In general, a horse’s lysine requirement is 4.3% of the dietary crude protein requirement. Protein and lysine needs change at different life stages.

Physiological amino acid requirements in horses have been studied in more detail only for lysine. Requirements for other amino acids are based on their typical levels in equine muscle tissue. Based on these data, methionine and threonine should represent 1.2% and 2.7% of crude protein intake.

Daily requirements for a 500 kg adult horse at rest or in light work

  • Crude protein: 630 g

  • Lysine: 27 g

  • Methionine: 7.5 g

  • Threonine: 17 g

Moderate or light exercise does not significantly change the horse’s protein requirement. In heavy or very heavy work, however, horses may require more protein and amino acids to support tissue recovery and energy supply.

Horses in heavy work

Daily requirements for a 500 kg horse in heavy or very heavy work:

  • Crude protein: 860–1000 g

  • Lysine: 29–35 g

  • Methionine: 8–10 g

  • Threonine: 19–20 g


Growing horses

Growing horses have higher protein and amino acid requirements to support rapid tissue growth. Their diet should contain 14–16% crude protein.

Daily requirements for weanlings and yearlings increase as they get older within the following ranges:

  • Crude protein: 720–950 g

  • Lysine: 29–50 g
  • Methionine: 8–11 g

  • Threonine: 18–29 g


Pregnant and lactating horses

Pregnant (9–11 months) and lactating horses require more high-quality proteins that meet their essential amino acid needs. Their diet should contain 10–14% crude protein. This is especially important during the last three months of pregnancy and the first four months of lactation, when protein requirements are highest.

Daily requirements for pregnant and lactating mares:

  • Crude protein: 800–850 g

  • Lysine: 28–50 g

  • Methionine: 8–16 g

  • Threonine: 18–31 g


Senior horses

Older horses (over 20 years old) may require higher protein levels to maintain body condition. Nutrient absorption is reduced in senior horses, which can mean that amino acids must be provided in higher amounts so the body receives them adequately.

In older horses, increasing protein intake must be done carefully. Supplemental amino acids should be increased slowly and only if the horse has sufficient liver and kidney function to support higher protein intake. Excess amino acids are not stored. Instead, they are broken down into urea, which is excreted in urine and manure. This can cause horses to drink more water and urinate more frequently. If liver and kidney function is not adequate, this may be harmful to the horse.

Regardless of your horse’s age, workload, or physiological status, it is important to assess the whole diet before making changes. In addition to protein, it is essential to check the adequacy of energy, vitamins, minerals, and other nutrients.

The roles and sources of lysine, methionine, and threonine

Grains, seeds, and grasses contain lysine to some extent. Legumes, such as soy, contain plenty of lysine. Lysine is also found in fenugreek seeds and spirulina. The lysine contained in proteins occurs in the form of L-lysine, which can also be used as a standalone equine supplement.

Methionine is present in high concentrations in alfalfa, flax, rice bran, sunflower seeds, and beet pulp, where it occurs as either D-methionine or L-methionine. Threonine can be obtained, for example, from beans and peas, such as pea protein, which is also included in Chia de Gracia’s Muscle Up product.

Muscle Up 5 kg
Muscle Up 5 kg, 80,50 €

Products to support the horse’s musculature

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