While EPSM isn't curable, diet and regular exercise can diminish or halt the muscle destruction in affected horses. The basis of the preventive/restorative diet is sharp reduction of soluble carbohydrates in the ration and the inclusion of fat when roughage alone can't supply all of the horse's energy needs. Dietary fat can be vegetable oils, such as corn, soy and canola; animal-fat products designed for horses or pigs; or rice bran. The latter feedstuff, though by far the most expensive option, is only about two-fifths fat and may contain a great deal of undesirable starch along with the fat. For economy and palatability, vegetable oils tend to be the fat of choice in horse diets. Each EPSM individual is unique, so it's impossible to predict how long it might take for the dietary changes to effect positive changes. In Valentine's experience, some horses show improvement within weeks, while others take several months for their metabolisms to adapt to fat-derived energy. Horses with severe muscle wasting may take a year or longer to recover. For individuals who show no signs of improvement after six months, diet therapy is probably not going to be effective. In cases where diet therapy has brought about improvement, Valentine recommends that the low-carbohydrate rations remain in effect for the horses' lifetimes.
"The sooner this metabolic disorder is recognized, the easier it is to get it under control with diet," says Valentine. "The muscle changes build up over time, and some appear to be irreversible. The hardest cases to turn around are horses--usually drafts -- who have gotten to the point of lying down and being unable to rise without assistance. These horses have about a 50 percent chance of surviving the first four months of diet changes. Out of hundreds of horses I've worked with, only about a half-dozen did not respond to diet change, regular exercise and turnout."
As a Thoroughbred, Winston didn't match the textbook profile of a likely EPSM victim, yet Valentine has identified the metabolic disorder in many horses outside the most heavily muscled breeds. Winston's owner and veterinarian decided to forego the muscle biopsy and opted for the less definitive blood tests, which showed some slight variances from normal but nothing conclusive. They chose to change Winton's diet, which seemed so easy after all the testing the gelding had undergone for many other suspected diseases, including EPM and wobbler syndrome. Besides, the current nutritional wisdom holds that the low-starch, fat-supplemented diet would only benefit the horse's overall health whether or not EPSM was a factor in his locomotor difficulties.
Winston's daily ration is gradually being altered to include three cups of corn oil mixed with two pounds of hay pellets. Additionally, his alfalfa-hay intake has been reduced, but he continues to receive timothy hay free choice.
This article originally appeared in the September 2002 issue of EQUUS magazine.
Part One: What is EPSM