Making Sense of Feeding Sulfur

You have probably read at least one article talking about sulfur in the body as indispensable for protein production, integrity of skin/hair/hooves and nails, enzyme action, some B vitamins, production of substances like chondroitin sulfate and elimination of toxins. All of that is true, and more, but confusion reigns about how you should supply it.

Elemental inorganic sulfur is a brilliant yellow mineral.

If you are from Australia or South Africa you may have been told horses should be supplemented with inorganic elemental sulfur.  Regardless of where you are from, you probably have read that MSM or DMSO are sources of organic sulfur that will be available to perform all the important roles of sulfur in the body. Both are incorrect.

Horses may utilize small amounts of the sulfate ion present in their diet and water but their main source of sulfur, and the only form utilized by proteins and insulin, is the sulfur containing amino acids, the most important of which is methionine which can also be converted to cysteine and from there to cystine – the other two structurally important sulfur amino acids. The horse cannot make methionine from sulfur or MSM/DMSO, it has to be present in the  diet.

Sulfur bonds/crosslinks maintain structural integrity in protein hormones like insulin as well as the keratin in skin, hair and hooves.  These bonds don’t come from sulfur being inserted into the structure.   They occur between the sulfur groups of two cystine amino acids.  The sulfur needed to make sulfated compounds like chondroitin sulfate comes from the desulfurization of sulfur amino acids.

As an aside, ruminants like cows or goats can benefit from elemental sulfur because the organisms in their forestomachs will use it to make methionine just like plants do. When the bacteria pass into the stomach and small intestine, the methionine will be absorbed.  Horses ferment their food in the hind gut, where absorption of amino acids is minimal – if it occurs at all.

The true equine requirement for methionine is unknown but is probably between 1/4 to 1/3 of the lysine requirement.  Forage is the major source of methionine.  The National Research Council has recommended a sulfur intake of approximately 0.15% of the diet dry matter, although there is evidence this may be inadequate.  (Note: About 90% of the sulfur in a hay analysis is incorporated into plant protein amino acids.) Good quality hay grown on soil with adequate sulfur should meet the requirements of at least maintenance and low level exercise if there are no special needs but there is a mounting problem with this.

Sulfur was routinely incorporated into plant fertilizers until increasing industrialization began sending large amounts of sulfur into the air. This “acid rain” provided an excellent source of free sulfur for plants but caused many other problems.  Sulfur emissions have been tightly regulated since the 1980s and 90s, with the result that soil sulfur is dropping.  A hay analysis crossed my desk this week that had only 0.04% sulfur.  These hays will have low protein, low methionine and the potential for high nitrate levels.

Taurine is another sulfur amino acid ultimately derived from methionine that plays many important roles in the nervous system, detoxification, liver function and metabolism.  Increased levels may be needed by horses with abnormal glucose metabolism to support the body in avoiding harmful interactions of glucose with body tissues, including nerve damage.  Taurine also helps maintain neurotransmitters responsible for a stable, happy mood.

When methionine intake is known to be low, or suspected from things like poor hoof quality, supplementation of 5000 to 10,000 mg (5 to 10 grams) per day for the average size horse is reasonable.  For situations that may benefit from taurine support, this can be supplemented directly in similar amounts.

Eleanor Kellon, VMD


About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions,, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition .
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12 Responses to Making Sense of Feeding Sulfur

  1. Betty says:

    I’ve read that sulphur ingestion will fend off lice…
    Any thoughts on this?..


  2. Pamela O’Donnell says:

    Can I add calendula flowers to my horses diet to supply him with sulphur and will it have a positive impact on his hooves please?


  3. Patrice Sager says:

    In goats sulfur in the presence of Molybdenum in the gut can then bind with copper and carry it out of the body. Is this true for horses too.


  4. Beverley Schutte says:

    HI Dr Kellon, ultimately, which is the best most effective form of feeding Sulfur. And where would we locate same. I see also Magnesium is best suited to stressed horses, best form of feeding?


    • Dr. Kellon says:

      Horses should get their sulfur from the sulfur amino acids, especially methionine. Horses absorb inorganic magnesium from most sources very well. I use magnesium oxide or magnesium carbonate.


  5. Linda says:

    Hi Dr Kellon – Thank you for this perfectly timed article, I am currently feeding 5gm of Methionine per day, is it OK to feed Taurine too. I suspect it will benfit one of my horses who struggles to relax and when she does relax she can appear ‘down’ – thank you


  6. Amber says:

    Hi their I am a lil confused with this article?. Should I stop the msm my horses are on two of them have been on it for twelve months. I have been using it as anti inflammatory for them as my trainer told me to use.
    Please any information would be wonderful. If I have to stop the msm what could I use in place of it please


    • Dr. Kellon says:

      Don’t stop it! MSM does have documented anti-inflammatory effects that have nothing to do with supplying the body with sulfur. It is an anti-inflammatory chemical that just happens to contain sulfur.


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