MSM (methylsulfonylmethane) is a naturally occurring form of sulfur that is found in plants and animals. MSM is used to support joint comfort in aging horses and performance horses.
Horses and other mammals cannot utilize pure sulfur in its elemental form. MSM is an organic sulfur compound found in fresh alfalfa and grains. It has high bioavailability and is safe to consume.
Sulfur is involved in many metabolic functions including carbohydrate metabolism, protein synthesis and protection from oxidative stress. It is also a component of glucosamine and collagen, both components of healthy connective tissue and cartilage in your horse.
Horses that are deficient in sulfur may experience inflammatory or degenerative issues like slow recovery from exercise, poor hoof quality, or joint pain.
Horses with arthritis, poor hoof condition, or aging horses are likely to benefit from MSM supplementation. It may also slow the progression of arthritis by preventing cartilage degradation, as shown in human studies.  
MSM has benefits for heavily exercised horses by minimizing oxidative damage and inflammation allowing their muscles to recover quickly. It is frequently given to high-level performance horses to keep them in peak competition condition.
Toxicity from MSM has not been reported in horses. It is derived from the natural compound DMSO (dimethyl sulfoxide). Both MSM and DMSO have been used as supplements for horses since the 1980s.
Why do Horses Need MSM?
MSM is primarily consumed as a highly bioavailable form of dietary sulfur. Sulfur is an essential macromineral that represents ~0.3% of total body weight in horses. It is required for the formation and proper functioning of proteins.
The NRC recommends a minimum sulfur intake of 0.15% of dry matter intake. Good quality hay and forages are likely to meet the minimum requirement for maintenance and leisure horses. Older horses or those that are heavily exercised would likely benefit from additional MSM for comfort and optimal performance.
Horses and other mammals obtain sulfur in the diet primarily in the form of two sulfur-containing amino acids called methionine and cysteine. Methionine is required in a horse’s feeding program because they can not synthesize it internally or endogenously. Cysteine can be made from methionine in the body. 
These amino acids are important building blocks for proteins. Cysteine molecules within proteins form connective links to each other that help the protein fold into the correct shape. This helps proteins such as enzymes, hormones, and structural proteins function properly and keep cells healthy. 
Collagen and glucosamine are the most abundant proteins in connective tissues such as ligaments, tendons, and within hooves, and joints. They are very high in the sulfur-containing amino acid cysteine.
When sulfur is low in the horse’s diet, the structure of collagen and glucosamine might be unstable making hooves and joints weak. This can cause pain and poor performance.
To understand whether your horse is meeting its sulfur requirement, you can submit your horse’s diet for analysis and one of our nutritionists will be happy to provide a complementary review.
MSM Benefits for Horses
When tissues require sulfur, cells break down proteins to release methionine and cysteine which are further broken down to release their sulfur content. These amino acids are then no longer available to make proteins.
Adding MSM to the diet as a readily available source of sulfur spares methionine and cysteine from being degraded, making them more available for protein synthesis. Supplementing with MSM also has direct therapeutic effects on its own.
Below are the top 9 benefits of MSM in horses:
- MSM is involved in making the detoxifying antioxidant glutathione, one of the most important intracellular antioxidants. Having enough glutathione keeps tissues healthy, especially when they are stressed by exercise or disease.
- It reduces oxidative stress after exercise, which could improve recovery after heavy work. It is also purported to increase circulation which may further support muscle recovery. 
- MSM decreases exercise-induced inflammation, which may support recovery and improved performance. 
- It helps with pain relief (analgesic effect) in heavily worked horses and can improve their comfort. 
- MSM helps support joint mobility in horses struggling with joint discomfort. 
- This macronutrient can improve your horse’s gait and stride, making walking and riding more comfortable.
- MSM could support a healthier coat by donating sulfur to keratin.  Keratin is a protein that acts as a primary structural component of hair, hoofs and skin.
- In humans, there is evidence that MSM can support a healthy respiratory tract. Horses that have allergies to dust, pollen, or molds might breathe easier with MSM and avoid bouts of heaves. 
- MSM supports the immune system during times of stress or disease. There is evidence in humans that it may improve injury healing and recovery from illness. 
Signs That Your Horse Might Benefit From MSM
- Puffiness around a joint, particularly the hocks
- Warmth or pain in a joint
- Changes in how the horse moves; might have a shortened stride, walk with a hollow back and raised head
- Resistant to performing tasks that were previously easy to do
- Your horse needs a longer time to warm up and not be stiff
Other reasons to consider adding MSM to the diet include:
- Your horse has respiratory allergies like heaves and poor breathing or coughing
- Horses with COPD (chronic obstructive pulmonary disease) might benefit from 20 g per day MSM
- Stressful periods like transport, competition, heavy training
Many horses could benefit from MSM supplements in their diet to provide extra sulfur to support healthy tissues. Consult with an equine nutritionist or veterinarian to determine whether this supplement is right for your horse. Submit your horse’s diet for analysis and our nutritionists will be happy to review your feeding program.
Results for Performance Horses
There is growing research to support the benefits of MSM for racehorses and other equine athletes involved in competition and rigorous training.
Dr. Ron Riegel, DVM at the Ohio State University conducted a study on MSM supplementation for post-exercise recovery involving 30 racing Standardbreds. Horses received either 10 grams or 20 grams of MSM per day for eight weeks. 
At the end of the treatment period, horses receiving higher doses of MSM were showing to have less inflammation and muscle soreness as measured via thermography. They also had lower levels of AST (aspartate aminotransferase) and CK (creatine kinase), two key markers of muscle damage.
All horses receiving MSM treatment saw an improvement in their average training time. The group given 10 grams per day experienced a two-second improvement in their times while the group given 20 grams per day saw a 2.62 second improvement. This suggests that MSM has benefits both for exercise recovery and for athletic performance.
Similar beneficial effects of MSM were also found in a study conducted by Marañón and colleagues in 2008. It was found that MSM administered at 8 mg/kg (just 4 grams for the average-sized horse) significantly reduced exercise-induced oxidative stress in 24 jumping horses. 
How Much MSM to Give Your Horse
MSM is a white, tasteless powder that horses readily eat when top-dressed on their feed. It can be purchased in bulk quantities through Mad Barn, at a cost of $22 per 1 kg.
To determine the best dosage of MSM to feed to your horse, it is recommended to consult an equine nutritionist or veterinarian. The dose your horse needs will depend on their current condition, reason for taking MSM and their bodyweight.
Some products recommend a daily dose of 2 grams of MSM per 100 kg of body weight for horses and ponies. However, a higher amount may be required initially to observe a therapeutic effect.
A dose of 20 g per day for the average-sized horse has been shown in research studies to have an anti-inflammatory benefit. 
You may choose to begin with a high loading dose until you see improvements in your horse’s condition. Once improvement is noted, you can lower the dose for maintenance.
Combining MSM with glucosamine and chondroitin sulfate is safe and might provide further benefit for maintaining healthy joints. Research in humans has demonstrated a synergistic effect when combining these supplements. 
Side Effects and Toxicity
There are no known side effects for MSM supplements in horses. In Riegel’s study including 30 horses supplemented with 20 g per day MSM, no abnormal blood chemistry, allergic reactions, or diarrhea were noted. 
In a report from 1981, horses that were accidentally fed between 200-400g of flowers of sulfur (>99% sulfur), had the following symptoms: 
- Lethargy within 12 hours
- Yellow, frothy discharge from the nares
- Jaundiced mucous membranes
- Laboured breathing
Flowers of sulfur is an industrial, elemental form of sulfur that is very different from MSM. These reactions are unlikely with MSM even at high doses.
Caution should be used if administering MSM to horse that have been diagnosed with blood clotting disorders or take medications that may affect clotting. Although evidence in human medicine is limited, The Arthritis Foundation advises against the use of MSM in people under these circumstances.
Before altering your horse’s feeding program to add MSM, we recommend consulting with a professional equine nutritionist. You can submit your horse’s diet for analysis one of our nutritionists will be happy to provide a complementary review.
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- Riegel R.J. The correlation of training times, thermographic and serum chemistry levels to provide evidence as to the effective of the use of oral Alavis msm (methylsulfonylmethane) upon the musculature of the racing Standardbred. Nutraceutical Alliance Conf. Proc., Carolwood Corp., Greenville, PA, 2001.
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- Muizzuddin, N. and Benjamin, R. Beneficial Effects of a Sulfur-Containing Supplement on Hair and Nail Condition. Natural Medicine Journal. 2019.