Equine Veterinary Science, September 1983
Reprinted with permission

There is a dearth of scientific literature regarding feed additives and supplements for the horse. One reason is that little work has been done in this area. But, perhaps, a more important reason is that most studies in this area are done by commercial feed companies that wish to guard their secrets.

I believe that when exciting information about new equine feed supplements surfaces, everyone in the horse industry would like to know about it. Therefore, I pass the following information along that was sent to me from Dr. John Metcalf.

John is an equine practitioner in Auburn Washington. He has pioneered the use of dimethylsulfoxide (DMSO) in horses. Some 20 years ago he was asked by Dr. S.W. Jacob to try this promising drug on horses. Dr. Jacob had been involved in research with the drug in humans. Since then, John has used it on a variety of cases. He has given it IV and tried various concentrations topically.

Now John has another interesting story about a substance chemically similar to DMSO. He was asked to try this substance much in the manner he first tried DMSO years ago. His communique to me is printed below. WEJ

John Metcalf, DVM

MSM, a new dietary supplement, is a metabolic end product of Dimethyl sulfoxide, DMSO, available in liquid and gelled forms, is a standard therapeutic modality in equine medicine today. While the therapeutic value is generally well accepted in our profession, its use has side effects to the patient and veterinarian, which include skin irritation and dryness, itching, together with the maltaste and offensive breath imparted with skin contact.

This communication introduces veterinary medicine to a new, basic development stemming directly from ongoing DMSO research. Evaluation is yet in the early stage, but findings to date suggest that the stable metabolite of DMSO negates the nuisance type side effects, while providing interesting health normalizing actions in man, the horse, and the dog.

Let me preface this preliminary report by admitting that my conclusions of the case histories which follow are subjective observations, not following a carefully controlled double--blind protocol. Fortunately, this stable metabolite of DMSO presents those physical and chemical properties required to conduct valid controlled studies, and these will follow. I have, however, been in practice for 30 years, so my experience serves, in a real sense, as the historic control.

The reason for authoring this preliminary report is that I am genuinely excited about the potential of this new substance, and hopeful of stimulating other veterinarians to evaluate and possibly confirm my initial findings with controlled evaluations. I use the term "substance" with special purpose since the subject of this paper better qualifies as a dietary supplement rather than as a drug.

I was in practice in Portland, Oregon when the medical benefits of DMSO were discovered some twenty years ago by Robert Herschler and Stanley Jacob of the University of Oregon Medical School. They, at that time, were somewhat apprehensive about the effects of the medication on some medical problems shared by man and horses. I was pleased to be invited into the study evaluating the effects with my equine practice.

Today I have little reluctance using DMSO with nearly any condition presented in animals since DMSO demonstrates a remarkable margin of safety and is free of serious side effects. One major problem with DMSO, however, is the imparted odor and other nuisance-type side effects which essentially blocks all manner of doubleblind type contorolled studies. The team at the Oregon Medical School has spent a great deal of time developing DMSO formulae with minimal nuisance-type side effects.

During this research towards a side effect free DMSO, Herschler and Jacob developed the dietary supplement, which is the stable, odorless DMSO metabolite. The substance is methyl sulfonylmethane, conveniently abbreviated as MSM. Do not confuse MSM with the new feed additive DMG (dimethylglycine). While MSM, recognized as a normal dietary factor of vertebrates, should be considered in the dietary factor category, it possesses certain bio-medical properties similar to DMSO together with additional biological activity not possessed by DMSO. It is most interesting that MSM has no exceptional activity, in vivo, where biological normalcy is presented. The original paper on the subject referenced MSM as factor N, implying the property of returning the abnormal health state to normal.

Chemically, MSM is DMSO with one added, stabilizing atom of oxygen onto the sulfur, i.e. CH³SO²CH³. Being ubiquitous to the diet of all vertebrates, MSM (and precursors) derive from vegetables, fruit, fish and meat. Any processing of a foodstuff, even the drying of alfalfa, may drive off a portion of the fugitive MSM. Physically, MSM is an odorless, white crystalline, water soluble molecule. Interestingly, one of the richest sources of MSM in the diet of mammals is milk. The first paper by the developers of this supplement¹ describes a number of health normalizing activities attributed to increased MSM in the diet.

My evaluation of MSM began during May of 1983. The intent of the developers in supplying the first MSM to me was to determine any possible effects with the unhealthy horse. At that time it had been studied rather extensively in man. I elected to evaluate the supplied crystalline MSM on myself. Much to my surprise, I found that my allergy problem was helped and that I had freer breathing. I had been through allergy testing some months before and was found to have a severe allergic reaction to just about everything having to do with the horse, including the horse itself. Since my practice is limited to horses, this allergy was a significant problem. After starting to add MSM to my diet, I felt better than I had in years.

Not convinced that my improvement was attributable to MSM, I withdrew added MSM, and returned to the earlier antihistamine therapy. My condition deteriorated. I again began to add 2 grams of MSM to my daily diet as a split dose and rapidly improved.

Because of this personal experience, and being an equine practitioner, the possible merit of MSM with the bleeding race horse came to mind. It seems logical that any agent that will improve pulmonary function stands a good chance of helping the bleeder. Beyond the pulmonary effect of MSM, it is also a mild diuretic. Presently very little of my practice is race track related, therefore no extensive testing of MSM with bleeders is underway. There are limited studies in progress, and hopefully results will justify a further report on MSM in equine practice.

My evaluation of MSM with the horse was not a straight line venture. After noting desirable benefits personally, I next decided to try it with my own eleven year old black lab. She has severe arthritis, particularly involving the hips and has been maintained on 400 mg of phenylbutazone per day. Her condition has been so severe, she frequently required help gaining her feet. We started adding a heaping teaspoon (6-7 grams) of MSM to her food B.I.D.; stopping the phenybutazone. For about a month, there seemed to be no benefit. Then she gradually improved, and now gains her feet regularly without help.

Even though my practice is limited to horses, the horse owners frequently ask questions about their dog problems. For this reason, four additional dogs with similar histories to mine have been given the same measure of MSM simply added to the food. There is a general consensus that MSM has turned back the clock on all five - to their soundness state of roughly three to four years ago.

Beyond the general improvement in the active state of these five dogs, it has been noted that with MSM added to their diet the hair coat improves in appearance and the toe nails seem to grow faster. Personally, my own fingernails require clipping about twice as often since increasing my intake of MSM beyond that normal to my diet.

Following this personal observation, it came to mind that MSM might be of benefit in the horse with the poor growing, flinty foot. An evaluation of the idea is underway, and it looks favorable, but it is too soon to report conclusively.

One additional observation made by a dog owner is interesting. His old female would consistently leave brown, killed grass spots wherever she urinated on the lawn. Since MSM was added to her diet there is no grass browning following urination. A study is underway to determine physical (such as pH) as well as chemical changes attributable to MSM.

Two world class human distance runners ingesting up to 4 grams per day of MSM in divided portions contend that MSM reduces the time required for recovery from a maximum competitive performance effort.² Recovery time to normalcy is about 25 percent of their pre-MSM experience. One must wonder what applications MSM might have for the race horse.

The MSM supplied to me thus far is received in purified crystalline form. Before use, I have the individual charged with administration dissolve the crystals in a small amount of hot water. MSM is readily soluble in warm water. It is then poured over the feed. No horse, nor dog for that matter, has demonstrated any reluctance in feeding.

The supplier of MSM advises they are formulating a high energy MSM content supplement which will make MSM even easier to use.

The first horse studied was one of my own in hunter training. The four-year-old horse had been unsuccessful in race training, having a history of chronic muscle soreness. Before MSM was added to his feed he was reluctant to do his job - ears back with frequent tail action. This horse, and all other adults studied thus far receive 12-15 grams twice daily in their feed. With this horse it took about a week to see a significant change. He is now a different animal, appearing to enjoy his job.

The second trial was with a yearling filly that moved like a wobbler or herpes victim. This filly was to be examined shortly for a select thoroughbred yearling sale. The owner was unwilling to allow the work-up required to determine a specific diagnosis. With the hope that it was herpes involvement, MSM was given at a level of 6-8 grams BID. The filly went through inspection and was passed by a tough inspector. The rational for trying MSM with this case stems from success using intravenous DMSO with a few herpes incoordinate individuals. Systemic DMSO not excreted by the renal pathway is enzymatically converted to methyl sulfonylmethane or MSM. It is doubtful whether one could successfully treat the wobbler problem with MSM.

Another condition responding exceptionally well to the MSM supplement approach is epiphysitis. I have treated seven individuals with confirmed diagnosis, and each has improved much faster than with conventional therapy. With these young horses, the supplement addition in each case was 6-8 grams added twice daily in the feed.

Calcium/ phosphorous balance is critical in the horse, where these elements comprise roughly 70 percent of the mineral content of the body. Neither calcium nor phosphorous deficiency is desirable. Deficiency can cause a stimulation of excessive secretion of parathyroid hormome resulting in a dietary deficiency condition termed nutritional secondary hyperparathyroidism. Calcium denied for bone development results in an enlargement of structurally defective fibrous tissue. The condition results in a stress inflammation termed epiphysitis. That MSM corrects this condition suggests the supplement moderates basic mineral balance.

The most dramatic epiphysitis case was a filly, again being prepared for the select sale. When first seen she appeared extremely sore - with marked reaction on palpation, and was reluctant to come out of the stall. The farm manager facitiously said, "no hurry on this one Doc, she doesn't get inspected for a week." Her total intake of MSM during this week was roughly 100 grams. She was inspected after a weeks treatment and passed.

Two other conditions responding to a dietary increase of MSM are acute laminitis and early navicular disease. As one example, my daughter's hunter pony had to be scratched from her last two classes (while on phenybutazone) in her last show because of a navicular problem. The horse, on 12 grams of MSM B.I.D. for one month showed sound in 8 classes over fences and 7 flat classes over a four day period. She now appears totally sound, and will be followed to determine whether the effect is lasting.

To date, MSM has been provided to about 100 horses presenting a variety of disorders. Many are still being followed. Only a select few cases are described here to illustrate the range of problems seemingly responsive to MSM.

A filly foal was seen with marked pleuritis, demon-strating no active infection but extremely noisy lungs. MSM was added to the feed at 12-14 grams/ day as a split feed addition over five days. No medication was used in conjunction with the MSM. The fibrous pleurisy cleared and her lungs were sound-free after the fifth day.

A yearling filly had an on-going problem with a history of frequent recurrent digestive tract disturbances beginning when she was a suckling. She seemed to respond to treatment with cimetidine, aloe-vera, and coating agents. With treatment termination, she demonstrated varying degrees of discomfort within a short time. MSM has been supplemented in her diet at 12-14 grams/day as a split addition for approximately ninety days and is problem free. A second example in this general category of disorder is of a suckling with signs of acute gastritis responding well to cimetidine. Symptoms, however, returned when treatment was discontinued for 10 days. The foal has been given a combination of MSM and aloe-vera over a ten day period and appears to be again in good health.

I trust that my peers recognize and understand my purpose in providing this preliminary report on a new mode and method for the treatment of disorders seen in veterinary practice. I sincerely hope the reader also appreciates the potential value of MSM in maintaining an animal in good health, probably at a lower supplement levels than were used in this study.

1. Jacob, S.W. & Herschler. R.J. (1983) Dimethyl Sulfoxide after Twenty Years, XIII-XVII. Annals of the N.Y. Acad. Sciences. Vol. 411, Biological Actions and Medical Applications of Dimethyl Sulfoxide. J.C. de la Torre Ed.
2: Jacob, S.W. (Personal communication).