Equine Cushings and "Cushings - Like Syndrome"

Dietary Recommendations

By Melyni J. Worth, PhD.

Cushings Disease is a condition of older horses where a tumor in the anterior pituitary in the brain causes an overproduction of Adreno-Cortical Stimulating Hormone (ACTH), which in turn causes an over-stimulation of the Adrenal glands. These glands produce the natural endogenous steroid, Cortisone. The symptoms of true Cushings are the ones of chronic hyper-steroidism. True Cushings usually affects horses in their early to late twenties, and the symptoms include an exuberantly thick coat that does not shed out in warm weather, loss of muscle tissue, weight gain in the neck (cresty neck), lumpy fat on the shoulders and tail head, and a tendency to founder.

In recent years we have begun to recognize another condition that looks a lot like Cushings, but which happens much sooner in life. Although many of the symptoms are the same, these horses do not have the excessively high ACTH levels. These horses with Cushings-Like Syndrome often turn out to be insulin resistant, in other words, they have a kind of equine Type II diabetes. In this condition, the cells are unable to process glucose due to an inability to respond to the hormone insulin.

First of all, you have to differentiate between the true Cushings horse and the Cushings look-alike horse that will have some or all of the same symptoms, but low ACTH levels. Modifying their diet helps equines suffering from both problems, but there is no long term improvement for the true Cushings horse, because of course the diet does nothing to eliminate the tumor, which will keep on growing. The diet will minimize the symptoms but it is only a matter of time before the ATCH levels become overwhelming. The Cushings-like Syndrome horses should get to "normal" and stay there with this diet.

This is my experience, and what I recommend for the Cushings-Like Syndrome horses/insulin-resistant horses. I hasten to point out that this MY experience - others may have different results. I have no hard scientific data to prove anything but I have fed this to about 700 horses with to varying degrees of success; so all the following information is anecdotal but supported by sheer numbers.

Primarily, I recommend increasing the Magnesium and Chromium intake on these horses as follows: approximately 2.0 grams Magnesium per 100 pounds of body weight per day, and .7 to 1.4 milligrams of Chromium per 100 pounds of body weight per day. Translation - for an average sized horse with a body weight of 1,000 pounds - up to 20 grams of Magnesium and 14 milligrams of Chromium per day. You will have to adjust these numbers accordingly for significantly different body weights. These should ideally be in conjunction with each other, but the Magnesium intake is the key. I prefer to use my own QuiessenceTM , which is a pelleted supplement that contains Magnesium as a chelate for maximum absorbability and Chromium as a salt, because the Chromium chelate form is not legal for use in livestock in the US. If you cannot get QuiessenceTM, I suggest using plain Magnesium Oxide as a substitute. Whatever else you do, the most important step to take is to raise the Magnesium intake.

Keep the horse on the high Mg/Cr until you get a remission of symptoms - this usually takes 4-6 weeks. If the horse is not getting enough Magnesium, then the improvement will either take longer or occurs once the Magnesium intake is further increased. By remission of symptoms, I usually mean a reduction in the thickness and size of the fat deposits on the neck, shoulders and tail head, and an overall weight loss if desired. In some of the horses using this supplementation, we have had reports of improvements in soundness - moving more freely and comfortably. This may be attributed to Magnesium increasing the peripheral circulation to the extremities (feet), but these results seem to vary widely from horse to horse. Once you get the horse to a more normal appearance, then you can drop the Magnesium levels to 10 grams per day, UNLESS the neck starts to build up again - if it does, increase the Magnesium intake back to 20 grams. Use the neck thickness to determine the Magnesium intake.

I also suggest that the horses go onto a Low Glycemic diet - that is, a diet low in simple carbohydrates. This diet is primarily high fiber - hay, sugar beet pulp, soy hulls or what ever you can find that is low in simple carbs. Then, you add one good vitamin/mineral/essential amino-acid supplement. My recommendation is the one I make one called LinProTM, is has all the vitamin/mineral/essential fatty acids/essential amino-acids in it. If you can't get LinProTM, I recommend using a flax-based feed supplement (for the essential fatty acids) with chelated minerals, and a supply of essential amino-acids, most specifically, methionine, lysine, threonine, and tyrosine. The best way to provide those essential amino acids, assuming you don't want to run about with endless bags of white powders, is to go for a VERY high-quality protein source. Your best bet would be casein (milk protein), egg whites, or extremely high-grade vegetable protein (Canola meal). If you use soy, cotton or flaxseed meals, they need to be fortified with amino acids.

If the horse cannot maintain weight on the high fiber diet with the protein/vitamin/mineral supplement, then and only then, do you add in more calories as fat. I like my fat sources as unprocessed as possible, so I prefer oil seeds like flaxseed, whole roast soy, or rice bran. I really don't like cups and cups of oil of any kind, but if that is what you want to feed, then at least it will add extra calories.

That is my recommended diet for Cushings horses and Cushings-Like Syndrome horses. It is also a good diet for horses with EPSSM (Equine Polysaccharide Storage Myopathy) and RER (Recurrent Exertional Rhabdomyolosis), except that the RER horses often need higher calorie intakes and thus we add in something safe like whole oats or lots of rice bran.

Raising the essential fatty acids intake is a good thing for all horses, and raising the Magnesium intake is also a good thing for most equines. I use 2-8 oz. of whole flax seed per day to raise the EFA levels. Raising the Magnesium and EFA levels is a good idea in any horse prone to founder, especially in the spring when the richest grass comes out. There are some calories in the Flaxseed, which is good, but I don't think you should feed more than the 8oz. per day no matter how big or hard working the horse is. If they still need more calories, then I'd go to rice bran or whole roast soy, and only after that to oils.

In summary, increase the horse's Magnesium intake, if possible in conjunction with Chromium, and reduce the level of simple carbohydrates in the diet. Use a good quality vitamin/mineral supplement, ideally one that also supplies essential fatty acids and essential amino-acids.

Dr. Melyni Worth Ph.D. - 2007 (c)


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