Changes to Expect after Switching to EPSM Diet

by Beth A. Valentine, DVM, PhD

Although it's impossible to predict exactly what you might see in your horse after you change its diet, the following information is based on observations we and horse owners have reported in biopsy-confirmed and suspect EPSM horses following diet change.

As with any diet change, the horse's metabolism will need time to adjust and "gear up" to utilize the fats. Some horse owners have reported horses "bouncing off the walls" after the diet change. Since higher fat diets have a calming effect in normal horses, a horse that is "bouncing off the walls" after diet change is one that most likely really needs this type of diet. The horse suddenly has the energy it has been missing, and it is simply showing you that it feels good. Give such a horse plenty of turnout with a month or two to get its brains back before putting the horse back in work. If too much energy is a persistent problem, adjustments of other parts of the diet to decrease total daily calories may help.

If your horse has a problem with tying up, you are well aware that these episodes are unpredictable. We believe that 2 to 4 months are needed before the muscle metabolism adapts to the diet change. Some horse owners have seen improvement within a few weeks, usually reported as an increase in energy. Some owners report a longer stride and better way of moving within a few months of diet change.

Interestingly, in some horses that have experienced tying up or other problems due to EPSM, after the horse as been doing well for one to 4 months, it may experience one or more repeat episodes of tying up or other problems. These episodes are generally milder than episodes prior to the diet change. Don't panic if this happens to your horse—with continued diet therapy, control of the tying up problem continues to improve. We don't understand exactly why some horses have to go through this "hump" period.

If your horse has a loss of muscle and energy and/or a stiff gait, you may see an improvement in these problems beginning at one to 4 months following diet change, with steady improvement continuing for many months. Stiff hind limb gait is common in horses with EPSM, and may begin to show improvement within 2 to 4 months.

Shivers and generating a proper canter appear to be the most difficult problems to correct. But, with time and slow steady schooling, EPSM horses often learn to carry themselves at the canter. Horses with shivers or stringhalt may continue to have some noticeable abnormal hind limb action, even after long-term diet therapy. Backing may also continue to be difficult for severely affected horses. To date most horses with shivers have improved on diet change, sometimes dramatically.

If your horse has serious loss of muscle, a year or more may be required for recovery. A small number of these horses seem to go through a bad time at 2 or 3 months after diet change. If the disease is severe enough, even diet change may not stop the progression to severe weakness and recumbency with an inability to rise

Horses that have been previously back sore may show increased flexibility, with a decrease in signs of back soreness. Attitudes interpreted as grouchiness during work may improve. Some horses that have been reluctant to hold their feet up for the farrier find it easier to stand for hoof trimming and shoeing. If, after about 6 months of diet change you see no improvement, diet therapy will likely not be effective for your horse. If, on the other hand, your horse responds favorably, diet therapy must be maintained for the rest of the horse's life.

Beth A. Valentine, DVM, PhD, is involved with EPSM research and other veterinary matters at the College of Veterinary Medicine, Oregon State University. She is this site's virtual vet and co-author of Draft Horses, an Owner's Manual. This article appeared in The Evener 1998 issue of Rural Heritage.