Branched Chain Amino Acid Supplements for Horses: Do they Work?

BCAA Supplements
Potential Benefits
Research in Horses
When Not to Use
Muscle Support

BCAAs (branched-chain amino acids) are muscle-building supplements that have become extremely popular among human athletes. BCAA products are also being used in the equine industry to improve performance in sport horses.

Branched chain amino acids, including leucine, isoleucine, and valine, play a crucial role in protein synthesis, muscle growth, and energy production. These essential amino acids are not produced by the body and must be obtained through dietary sources.

Horses obtain some BCAAs from high-quality protein sources, such as alfalfa and soybeans. However, supplementation with higher quantities of BCAAs is purported to improve muscle recovery after exercise, reduce fatigue and improve body composition in horses.

Currently, there is limited research available to assess the validity of the claims made about BCAAs for horses. However, you can support muscle health in performance equine athletes by providing an appropriate amount of high-quality protein sources.

Branched Chain Amino Acid Supplements

BCAAs are a group of three essential amino acids – leucine, isoleucine, and valine – that are critical for building and repairing muscle tissue.

These three amino acids are grouped together because they have a unique chemical structure that consists of a branched carbon side chain connected to the main amino acid components.

Role of BCAAs in Muscle Cells

The branched-chain amino acids are also unique because they have special roles in skeletal muscle cell metabolism, including the following:

Unlike most amino acids which are broken down in the liver, BCAAs bypass the liver and are instead metabolized in muscle cells
BCAAs can be broken down in muscle cells and used directly as an energy source
Supporting insulin signaling in muscle cells ^[1]^[2]
Accounting for 35% of the essential amino acids found in muscle proteins
Stimulating muscle protein synthesis, with leucine being particularly effective in activating muscle-building pathways

Effects on Athletic Performance

Due to the effects of BCAAs on muscle metabolism, supplementation has gained popularity for its potential to enhance athletic performance. Leucine, isoleucine, and valine are believed to reduce exercise fatigue, decrease muscle damage, and increase muscle protein synthesis.

However, the research on BCAA supplementation in horses is limited, and the results from human studies have shown mixed findings.

Proposed Benefits of BCAAs

The proposed benefits of supplementing with branched-chain amino acids in horses include the following:

Improved post-exercise muscle recovery
Reduced muscle fatigue during exercise
Improved body composition

However, the evidence supporting these claims is controversial and inconsistent.

Improved Muscle Recovery After Exercise

BCAAs have been investigated for their potential to reduce exercise-induced muscle damage. During strenuous exercise, muscle fibers can experience microscopic damage, resulting in soreness, inflammation, and a temporary reduction in muscle strength.

Some studies report that individuals supplemented with BCAA had reduced markers of muscle damage and experienced less muscle soreness following exercise compared to those without supplementation. ^[3]^[4] However, the evidence is mixed.

Meta-Analysis

One meta-analysis reported on eight studies investigating BCAA effects on muscle performance, with four studies showing no evidence of improvement and four studies reporting a positive effect. ^[5] When these studies were further reduced to only include ‘positive quality’ studies, only one study of six showed positive benefits of BCAA supplementation for muscle recovery.

Another meta-analysis reported that BCAA supplementation reduced levels of muscle damage makers, but did not find that this translated to improved muscle performance post-exercise. ^[4]

Positive Results

In studies that did note a positive effect, the research indicates that BCAA supplements were more effective when:

Supplementation was in trained athletes rather than untrained individuals ^[3]
Post-exercise damage was low-to-moderate ^[3]^[5]
BCAAs were supplemented prior to exercise ^[3]^[5]

Reduced Exercise Fatigue

Some studies suggest that BCAA supplementation may delay the onset of fatigue during prolonged exercise. In theory, this could improve performance in endurance events and help sustain energy levels during training or competition.

Fatigue during exercise can be classified as central or peripheral, depending on the underlying factors involved. Central fatigue is associated with an overall reduced ability in the brain to stimulate muscle actions, while peripheral fatigue is caused by mechanisms that directly affect the muscles themselves

BCAAs are purported to improve both central and peripheral fatigue. While there is no strong research showing that BCAAs can reduce central fatigue, some research indicates that BCAAs may reduce peripheral fatigue by sparing muscle glycogen or reducing metabolic byproducts. ^[6]^[7]^[9]

Central Fatigue

Central fatigue occurs when the central nervous system (the brain) becomes inefficient at stimulating muscle cells. It is associated with an exercise-induced increase in concentrations of the inhibitory neurotransmitter serotonin.

BCAAs are believed to delay central fatigue by competing with tryptophan for absorption into the brain, thus reducing its uptake. Tryptophan is an amino acid required to synthesize serotonin. By reducing tryptophan uptake, BCAA supplementation could help delay central fatigue.

However, a meta-analysis of 31 human nutrition studies found no evidence to support this theory regarding BCAA supplementation and reduced central fatigue. ^[6]

Similarly, a study on rats supplemented with BCAA found no impact on central fatigue mechanisms. However, the researchers did observe improved performance delayed time to exhaustion in subjects receiving BCAA, but these effects were attributed to reduced peripheral fatigue. ^[7]

Peripheral Fatigue

Peripheral fatigue occurs when the muscles themselves have a reduced capacity to generate force during prolonged bouts of exercise. This may be caused by factors including the depletion of cellular energy sources, or the accumulation of metabolic byproducts such as ammonia.

Muscle cells rely on glycogen to meet the energy demands of physical activity. Glycogen is a stored form of energy that can be readily accessed and broken down into glucose when needed. However, muscles have a limited capacity to store glycogen, and as these reserves become depleted during prolonged or intense exercise, peripheral fatigue can occur.

BCAAs are believed to delay peripheral fatigue because they can be broken down in muscle tissue as an alternative energy source. When muscle cells use BCAAs for energy instead of glycogen, this delays the depletion of energy reserves in muscle cells. By sparing the use of glycogen, BCAAs may be able to delay the onset of peripheral fatigue.

Lactate Accumulation

There is some evidence to suggest that BCAA supplementation may improve peripheral fatigue. The previously mentioned meta-analysis of 31 nutrition studies did find that BCAAs can reduce lactate accumulation. ^[6]

Lactate is a byproduct of anaerobic metabolism that builds up in the muscles as glycogen is burned for energy. The buildup of lactate in muscle is thought to impair muscle function through peripheral fatigue.

By reducing lactate accumulation, BCAAs could help delay the onset of muscle fatigue and contribute to improved exercise performance.

However, the role that lactate plays in muscle fatigue has been called into question as recent research shows that lactate positively contributes to muscle metabolism. ^[8] It is not clear whether a reduction in lactate build-up has beneficial effects on muscle health or performance.

However, lower lactate levels could indicate reduced glycogen breakdown, suggesting that BCAAs may help by sparing energy stores in the muscle. Additional research is still needed to confirm these findings in horses.

Improved Body Composition

BCAA supplementation is purported to improve body composition, which refers to the relative proportion of muscle mass and fat mass in the body. Feeding BCAAs is proposed to support muscle growth and help preserve muscle mass under calorie restriction.

Restricting calorie intake is a common fat loss strategy, but it is also associated with a loss of muscle mass. Given that BCAAs play a vital role in the signaling pathways necessary for muscle protein synthesis, some suggest that supplementing with BCAAs could help mitigate the muscle loss commonly observed during a calorie-restricted diet. However, the data supporting this claim is mixed.

Preserving Lean Muscle Mass

One research study involving seventeen young adult males did find that the BCAA supplementation help maintain lean muscle mass while on a calorie-deficient diet. ^[10]

However, a more recent study using 132 adults found that BCAA did not preserve lean mass during weight loss. ^[11]

Increasing Muscle Growth

Even in the absence of calorie restriction, BCAA supplementation may not stimulate lean muscle growth if individuals are already consuming enough protein in their daily diet.

A meta-analysis examining twelve studies on the effects of BCAA supplementation on body composition concluded that there was no apparent increase in muscle mass associated with supplementation. ^[12]

Muscle growth is a complex and multi-factorial process, which may explain the variation in results seen in human studies. More research is needed to determine if and how BCAAs can support muscle maintenance in diets that are otherwise protein-deficient.

BCAA Research in Horses

Limited research has been conducted regarding branched-chain amino acid supplements in horses. However, there is a growing interest in BCAAs for horses, largely influenced by their widespread use among human athletes.

Circulating BCAA Levels

Many horse owners and trainers are interested in supplementing with BCAAs because research shows that exercise changes the circulating levels of BCAAs in horses.

One study found that horses participating in high-intensity exercises, such as show jumping, had lower concentrations of BCAAs in their blood during exercise. ^[13]

Horses have also been shown to increase the mobilization of BCAAs during long-duration exercises, such as endurance races. ^[14]

While this indicates that BCAAs do play important metabolic roles during exercise, it is still unknown if BCAA supplementation can enhance athletic performance.

Effects on Performance

One of the first studies involving BCAA supplementation in horses involved eight racing-fit Standardbreds. ^[15] The experimental group was provided with 18 grams of BCAAs one hour before training for four weeks. At the end of the four-week trial, the horses completed a performance test.

The study did not observe any significant differences in exercise-related metabolites or muscle enzymes between the treatment group. The researchers noted that, at best, BCAAs had a “mild effect” on energy metabolism. However, the amount of BCAA administered to the horses in the study was comparatively lower in relation to body weight than typical dosages used in humans.

In another study, horses in an exercise program were supplemented with 34 grams of BCAAs. The researchers observed that the BCAA supplementation alone did not have any significant impact on the gene activity of genes associated with skeletal muscle tissue. ^[16]

Similarly, another study involving exercised Standardbreds given 30 grams of BCAA supplementation found no difference in markers of muscle damage or muscle metabolism. ^[17]

This suggests that the BCAAs did not improve athletic performance in this group of exercised horses. Instead, the study found higher levels of blood urea, indicating that excess protein was simply being broken down and excreted. ^[17]

Immune Function

One study did find that BCAA supplementation in young racing horses improved levels of circulating immune cells. ^[18]

This implies that BCAAs have the potential to improve immune function, which is often compromised during high-intensity exercise and competitive activities.

Summary of Research Findings

Overall, there is currently no research showing that BCAAs can help improve exercise performance, muscle health or muscle growth in equine athletes.

However, there may be other benefits of BCAAs, such as in supporting immune health. Further research is warranted to help explain how BCAA can impact equine health and performance.

When Not to Use BCAA Supplements

There are certain situations when it is not advisable to use BCAA supplements. Exercise caution before adding protein to the diets of horses with insulin resistance or kidney dysfunction.

Branched chain amino acids should also not be used to replace other limiting amino acids in the equine diet.

Horses with Insulin Resistance

Supplementation with the BCAA leucine has been shown to stimulate insulin secretion in humans and sheep. ^[2]^[19]

In horses, the administration of a high dosage of leucine alongside a carbohydrate resulted in a heightened insulin response compared to the response triggered by the carbohydrate alone. ^[20]

These findings indicate that when fed alongside sugars, leucine has the potential to increase the insulin response in horses. As a result, it is advisable not to supplement BCAAs alongside high non-structural carbohydrate (NSC) meals in horses with insulin dysregulation.

Horses with Kidney Dysfunction

Diets that contain too much protein put additional strain on the horse’s kidneys, which is problematic for horses with kidney disease or impaired renal function.

When excess protein is consumed, it is broken down into nitrogenous waste products, such as urea and ammonia, during the process of protein metabolism. These waste products need to be filtered and eliminated by the kidneys.

To minimize the strain on the kidneys, horses with kidney dysfunction need a lower-protein diet. If the dietary protein cannot be limited, BCAA should not be supplemented. However, on a low protein diet, some essential amino acid supplement could benefit your horse. If you are unsure how to manage protein in the diet of a horse with kidney dysfunction, consult with an equine nutritionist.

In Place of Limiting Amino Acids

BCAA are essential amino acids, meaning they must be provided by the diet because the horse’s body cannot synthesize them. However, BCAAs are generally not a limiting factor for protein synthesis in most equine diets.

Limiting amino acids are the amino acids that are most commonly supplied below requirements in the equine diet. Among all the essential amino acids, lysine, methionine, and threonine are the ones most likely to be deficient.

It is crucial to ensure that these three amino acids are present in sufficient amounts in the diet, as their inadequate supply can impair muscle synthesis, even if high levels of BCAAs are supplemented.

Therefore, before adding branched-chain amino acids to your horse’s diet, consult with an equine nutritionist to ensure that the diet provides adequate amounts of limiting amino acids.

Three Amigos

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Optimal protein synthesis
Hoof & coat quality
Topline development
Athletic performance

How to Support Your Horse’s Muscles

While BCAA supplements are not a magic bullet, there are several effective ways to support your horse’s muscle health through feeding and management.

1) Feed Adequate Protein

Horses have different dietary protein requirements, depending on their stage of life, exercise level and other factors. A moderate-quality grass hay may provide enough protein for mature horses in light work, but growing horses or horses in heavy exercise may require additional protein from a legume hay, such as alfalfa.

An equine nutritionist can help you calculate your horse’s protein requirements to ensure their diet supplies enough of this macronutrient to support muscle health and performance.

It’s also important to avoid feeding excess protein. In addition to increasing the workload of the kidneys, excess protein may alter the horse’s gut microbiome, which has been shown to increase health risks in other species. ^[21]

Furthermore, higher levels of protein intake are not more efficient at stimulating muscle-building pathways compared to a meal with moderate protein intake. ^[22]

2) Feed High-Quality Protein

A high-quality protein refers to a protein source that exhibits good digestibility and contains all the essential amino acids in the appropriate balance. In other words, this type of protein is easily absorbed by the horse’s digestive system and provides all the amino acids that the horse cannot synthesize on its own.

Research in horses shows that providing a higher-quality protein source with an enhanced amino acid profile leads to increased activation of proteins involved in muscle-building pathways compared to feeding a protein source derived solely from forage. ^[23]

3) Increase Feeding Frequency Not Volume

Feeding horses multiple meals throughout the day, as opposed to one or two large meals, has been found to enhance digestibility. ^[24] Additionally, a higher feeding frequency has been shown to promote digestive tract health in horses.

Furthermore, research suggests that smaller and more frequent meals can increase the level of circulating amino acids in the bloodstream, comparable to that of a larger protein meal. This increase in amino acids is vital for activating the pathways necessary for muscle protein synthesis. ^[25]

Together, these findings indicate that smaller, more frequent meals not only contribute to improved digestibility but also effectively stimulate muscle-building pathways. ^[25]

Summary

While BCAA supplementation is purported to enhance athletic performance in horses, the research currently available does not conclusively show benefits for muscle recovery, body composition or fatigue.

Branched chain amino acids do play important physiological roles in muscle metabolism, but if your horse already gets sufficient protein in their diet, supplementing with BCAAs is not proven to have an additive benefit.

To support muscle health in horses, science points to providing a high-quality protein source at a level that is appropriate for your horse’s needs. Pay closer attention to the limiting amino acids, which are more frequently found to be deficient in the equine diet.