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Are Sulfur Blocks Safe For Horses?

Feeding your horse a well-balanced diet that includes all the correct vitamins and minerals it needs to be a healthy horse can be quite a daunting task and require careful planning. So, is feeding a sulfur block to your horse a safe thing to do?     

Sulfur blocks are generally safe for horses. Horses need sulfur for both joint and hoof health, and sulfur deficiency can lead to connective tissue problems. Sulfur is involved in many metabolic functions, and a lack of sulfur-containing amino acids would lead to weakness of the ligaments, bones, joints, tendons, and hooves. Other than feeding the usual salt licks, your horse will require sulfur in its diet.

Here is some more in-depth information on how to give the correct sulfur supplement to your horse.

Are Sulfur Blocks Safe for Horses?

Sulfur is an organic substrate and is closely associated with sulfur-containing amino acids methionine and cystine. Sulfur is an essential micromineral that represents 0.3 percent of the total body weight in your horse.

There are a large number of salt and mineral supplements available on the market to choose.  Most commonly used are plain white salt blocks, red mineral blocks, and rock salt on a rope.  Other mineral salt licks available contain selenium, cobalt, or sulfur.

Where horses graze naturally, they will derive their daily sulfur intake from natural plants. However, when horses are kept stabled for long periods and not allowed to graze naturally, they need supplementation. 

Fresh grazing provides adequate sulfur intake, but we cannot say the same for preserved forage.  Some quality of hay does not meet the desired protein levels, and so sulfur levels may vary.

Therefore, some horses who are stabled regularly and rely on preserved forage may be sulfur deficient.  Supplementation is essential to maintain and improve your horse’s health.  

With so many mineral licks and supplements available on the market these days, it is often hard to decide which one to use.

Although you can use mineral blocks easily, nowadays, mineral supplements come in powder form that can be added directly to your horse’s feed to give the correct measured daily dosage.

Using a mineral block is fine, but it doesn’t ensure the correct dosage.  Many factors could play a role in a horse not getting the right dose from a mineral block lick. 

MSM or Methylsulfonylmethane supplement

MSM is a form of sulfur that naturally occurs in many plants. MSM is an organic sulfur found in fresh alfalfa and some grains.  MSM is necessary for the formation and functioning of proteins.

MSM is prescribed for old and competing horses to relieve joint pain.  It maintains healthy connective tissue, bones, cartilage, and hooves.  It also helps keep healthy skin and coat in horses. However, MSM may do much more than this.

Horses with arthritis and poor hoof condition will benefit from MSM supplementation.  It is also given to heavily exercised horses to reduce inflammation allowing their muscles to recover more quickly.  It is frequently given to competing horses to keep them in top condition.

MSM is known as one of the safest horse supplements. Excess MSM is readily excreted by urine or in the feces.

What are the benefits of sulfur supplements for my horse?

The direct therapeutic benefits of giving an MSM supplement are plentiful.  It is the main factor in creating the detoxifying antioxidant glutathione.  Having enough glutathione is essential to keep tissues healthy. 

It also reduces tissue damage after vigorous exercise by preventing oxidative damage. Muscles recover more quickly.  Furthermore, it increases circulation, which also helps muscle recovery. 

It has an analgesic effect, thus aiding recovery and comfort in heavily exercised horses.

MSM improves conditions like hock arthritis and helps with tissue degeneration.

Horses receiving MSM have a healthier coat and skin because MSM supports keratin formation.  Keratin is the primary protein that is essential for healthy hooves, skin, and coat.

Giving this sulfur supplement helps horses prone to allergies because it also supports a healthy respiratory tract.

What signs of arthritis to look out for in older horses? 

Here are the symptoms If you have an older horse that shows signs of arthritis

  • Noticing signs of puffiness around the joints and most notably around the hock.
  • Pain or warmth on a joint.
  • When you notice changes in your horse’s movement, raised head, hollowed back, or shortened stride is all signs of pain—refusal to do regular tasks it usually did easy previously it could be signs of arthritis.
  • If the horse needs a longer time to warm up than previously during exercise, it could be arthritis.

Here are some other reasons to feed a sulfur supplement to your horse

  • If your horse suffers from respiratory allergies like coughing, low breathing, or heaves, it will benefit from 20 g of MSM per day.
  • You may also feed a sulfur supplement during stressful situations like competition, transport, and heavy training.
  • Avoid using steroids to treat inflammation. Horses on higher doses of MSM showed less pain and inflammation after intense training.
  • Feeding this supplement has also shown benefits for digestive upsets, but further research is needed.
  • Records show that horses with Equine Protozoal Myelitis (EPM) and Epiphysis greatly benefit from MSM.
  • It boosts the immune system and can have cancer-fighting abilities.

Mineral block lick vs. Powder supplements: the pros and cons

Mineral Block

Mineral blocks are easy to use and can be placed in a stall or paddock out in the field left for the horse to lick as he, please.  However, there are a few disadvantages of using a mineral block lick. 

Initially, mineral and salt licks are for cattle who have rougher tongues than horses.  A Horse’s tongue is much smoother and can quickly become irritated by repeatedly licking a rough surface and may not get the recommended daily dose.

Horses are known to get frustrated at the block licks by biting them to consume more, causing jaw and teeth problems.  Doing this can also lead to overconsumption.

Horses that overeat mineral block may exhibit signs of colic, diarrhea, frequent urination, and weakness.

During cold, freezing winter months, when mineral and water intake is vital, the cold lick can become even less inviting.  

Placing a community mineral block out for multiple horses in pasture might be enjoyed by some but denied to others if a bully is present.  

All mineral blocks placed outdoors should be protected from the weather and kept clean. 

If you place a mineral block in your horse’s stall and he splashes his water all over it, it will dissolve, and you won’t know how much the horse gets in.  In some cases, horses don’t touch the block lick for days, so you can never be sure exactly how much of the sulfur your horse digests.

Powder supplement added to feed.

Adding a correctly measured scoop of powder supplement to your horse’s feed ensures his daily intake, and you can be sure your horse gets his daily dietary need. Feeding MSM in powder form places you in control of your horse’s daily requirements and doesn’t leave anything to chance.

Flowers of Sulfur: what you need to know (Yellow Sulfur)

Flowers of Sulfur is an inorganic elemental form of sulfur and very different than MSM.  Research has shown that feeding this type of sulfur is 99% indigestible to horses.  Bioavailability is very poor, and therefore it is wasteful as a supplement. There are better sulfur supplements available on the market.

How much MSM do you give a horse?

To start, feed one scoop of 10 grams MSM twice a day for seven days per horse, then 1 scoop a day as a maintenance dose after that.

Are there any toxicity and side effects of MSM?

There are no side effects of MSM supplements in horses.  Even when higher than recommended doses of MSM were given to the horses, there were no side effects.  Studies done on more than 30 horses supplemented with 20 grams of MSM daily have shown no allergic reactions, diarrhea, or abnormal blood chemistry.

However, horses that accidentally fed on 200 to 400 grams of Flower of Sulfur showed symptoms of lethargy within 12 hours, yellow discharge from the nose, labored breathing, and jaundiced mucous membranes.

You should not give MSM to horses with these conditions

Horses that suffer from urinary tract stones, hyperglycemia, blood clotting disorders, or diabetics should not receive an MSM supplement.

Pregnant mares should not take MSM.


We have concluded that supplementing your horses’ diet with an MSM supplement is necessary and very safe, and beneficial.  MSM is a recommended absorbable powder supplement for maintaining healthy joints and supporting normal inflammatory response associated with daily training and exercise.  MSM can help your horse maintain and reach optimum health and boost performance.

In this article, we have already established, giving a powdered supplement that you add to your horse’s feed is a much better option to control the dosage and consumption of MSM than just providing a sulfur block lick.  However, whichever option you decide to choose is entirely up to you and, of course, your horse.

Anrie Diedericks

I've been around horses since I was 6 years old and started competing at the age of 9. Horses are my greatest passion and I am thrilled to be able to share my 23 (and counting) years of experience and knowledge with you.

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