Sulfur for Horses

Biotin.

Chondroitin Sulfate.

Insulin.

Methionine.

If you know anything about horse health or nutrition, at least some of these things (if not all of them!) should ring a bell.

They are all essential to your horse's health in one way or another...and they all contain sulfur.

Biotin is often supplemented for poor hoof health, chondroitin sulfate for joint health.

Insulin is a hormone your horse produces that works to regulate carbohydrate metabolism and it can cause big problems when it is not working right.

And last but not least, methionine is one of the essential amino acids, and usually the second-limiting one at that.

To reiterate, all these important substances contain sulfur.

In fact, so many important substances in your horse's body contain this mineral, that it makes up almost 0.15% of his body weight. For your average 1000 pound horse, that's 1.5 pounds! Of a mineral!

Two very important amino acids, cystine and methionine, both also contain this mineral. These amino acids are important because they make up part of the structure of almost every single protein in your horse's body.

As if that wasn't enough, they are also an important structural component of almost every enzyme in his body as well! Thiamin also contains it, and thiamin is important for carbohydrate metabolism, as discussed on its page.

Another important substance to your horse is heparin. It serves as an anticoagulant...

...in other words, it keeps your horse's blood cells from sticking together and creating clots in his blood vessels. Heparin also contains this very important mineral.

Dietary Sources

This macromineral is rather unique because your horse can only obtain it in organic form.

However, this generally isn't a huge problem, because most of it found in plants is organic...

...in fact, it is usually in the form of cystine and methionine, since plant proteins are also composed of those amino acids.

The inorganic form can be used to make a few of the sulfur-containing products we have mentioned, including:

  • Chondroitin Sulfate
  • Heparin
  • Insulin

One of the easiest ways to ensure your horse obtains enough of the organic form is to provide high-quality protein in his diet, such as that found in soybean meal (which is the main ingredient of most ration balancers on the market today).

Sulfur Deficiency and Toxicity

A deficiency has never been described in horses, and doesn't appear to be a likely problem in the average horse.

Toxicity also appears to be of little concern, due to the fact that it appears high levels of the mineral would be required to induce a toxic response.

However, if toxicity does occur, the results are dramatic in the cases of large overdoses. In 1981, a report was given¹ of horses that were 5 to 12 years of age that were accidentally given 200-400 g of flowers-of-sulfur. Flowers-of-sulfur are more than 99% sulfur, so essentially these horses were given 200-400 g of the mineral.

Within 12 hours the horses were extremely lethargic and almost all of them suffered bouts of colic. Many of them also had jaundiced mucous membranes and labored breathing. Two of the twelve horses also died as a result of this mishap.


Sulfur is a very important macromineral to your horse's health due to the fact that it is present in so many places in his body.

It is one of the most abundant minerals in your horse's body, and thankfully it is also very easy for your horse to obtain through diet.

Additionally, toxicity and deficiency appear to be of very little concern in the horse.


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¹Corke, M.J. 1981. An outbreak of sulphur poisoning in horses. Vet. Rec. 109:212-213.