MSM (methylsulfonylmethane) is a naturally occurring form of sulfur that is found in plants and animals. MSM is used to relieve joint pain in aging horses and performance horses. It helps maintain healthy connective tissue, cartilage, bones, and hooves. It also supports a healthy skin and coat in horses.
Horses and other mammals can not use pure sulfur. 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 which are necessary to maintain health connective tissue and cartilage in your horse.
Horses that are deficient in sulfur may experience inflammatory or degenerative issues like slow recovery from exercise, hoof problems or joint pain.
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 performance horses to keep them in top competition shape.
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.
MSM is regarded as one of the safest equine supplements. It has a short half-life in the body and excess MSM is rapidly excreted in urine and feces.
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 of proteins and for proper functioning of those 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.
Horses that are aging or 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 their stored methionine and cysteine 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 tissue damage after exercise by preventing oxidative damage, helping muscles recover quickly from exercise. It is also purported to increase circulation which may further support muscle recovery.
- MSM decreases exercise-induced inflammation, speeding up post-workout recovery and contributing to improved performance.
- It helps with pain relief (analgesic effect) in heavily worked horses and can improve their comfort. 
- MSM helps improve joint pain in conditions like hock arthritis. It may also have a preventative effect by reducing some of the tissue degeneration that can contribute to arthritis.
- This macronutrient can improve your horse’s gait and stride, making walking and riding more comfortable.
- Horses supplemented with MSM have a healthier skin and coat because MSM supports keratin formation. Keratin is a protein that acts as a primary structural component of hair, hoofs and skin.
- 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. It can improve injury healing and recovery from illness. It also acts as an antioxidant and can promote detoxification of harmful heavy metals.
Signs That Your Horse Might Benefit From MSM
Horses with arthritis are likely to benefit from MSM. If you have an older senior horse , look out for the following symptoms of arthritis and consider adding MSM to the diet:
- 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
- If you would like to avoid using steroids to treat inflammatory issues
According to Equimed, MSM is anecdotally reported to have benefits for horses with Equine Protozoal Myelitis (EPM) and Epiphysitis. It is also purported to have benefits for digestive upsets, but more research is needed to evaluate its efficacy for these uses.
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 recently 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. 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. The researcher concluded that horses engaged in intense training experience anti-inflammatory and analgesic effects from taking higher doses of MSM. 
Furthermore, according to Dr. Riegel, “Trainers reported that the [horses receiving 20 grams per day] had better hair coats, faster, and healthier hoof growthâ€¦”
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 $15 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 sources recommend an on-going dosage 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 has been shown in research studies to have an anti-inflammatory benefit.
You may choose to begin with a high loading dose (20 g per day) until you see improvements in their condition. Once improvement is noted you can lower the dose for maintenance to 10 grams per day.
Combining MSM with glucosamine and chondroitin sulfate is safe and might provide further benefit for maintaining healthy joints and hooves. Research has demonstrated a synergistic effect when combining these supplements.
For exercise recovery, research in jumping horses has shown benefits with 8 mg/kg of bodyweight (4000 mg for a 500 kg horse) of MSM along with 5 mg/kg vitamin C (2500 mg for a 500 kg horse) per day. These were given for 7 days leading up to competition until the end of competition. 
Side Effects and Toxicity
There are no known side effects for MSM supplements in horses. In a 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.
In ruminants, chronic elevated sulfur intake can impair copper absorption leading to issues related to copper deficiency. There is no evidence that this occurs in horses.
Horses that have a history of urinary tract stones, diabetic horses, animals with hyperglycemia or those with an allergy to shellfish should not be given MSM. 
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.
- Briggs, Karen. MSM and Inflammation . The Horse, 2002.
- Wong, Thomas et al. Small Intestinal Absorption of Methylsulfonylmethane (MSM) and Accumulation of the Sulfur Moiety in Selected Tissues of Mice . Nutrients, 2008.
- Briggs, Karen. MSM Helps Sore Muscles . The Horse, 2001.
- Maranon, Gonzalo et al. The effect of methyl sulphonyl methane supplementation on biomarkers of oxidative stress in sport horses following jumping exercise. Acta Veterinaria Scandinavica, 2008.
- Corke, MJ. An outbreak of sulphur poisoning in horses. Vet Rec. 1981.
- Equimed staff. Methylsulfonylmethane. Equimed, 2014.