Rural Heritage Vet Clinic

Dietary Recommendations for a Horse with EPSM

by Beth A. Valentine, DVM, PhD

Overhauling your horse's diet is the first line of treatment against EPSM. The goal of the EPSM diet is to decrease soluble dietary carbohydrates (grain) and increase fat. You want to provide 20% to 25% of total daily calories from fat.

The diet is safe for any horse and therefore may be used as a dietary trial to see if EPSM is the underlying cause of your horse's problems. If you decide to try it, however, ask your veterinarian to work with you during the trial.

The horse's hay and pasture are generally not altered, but the addition of fat to the diet is critical, regardless of whether the horse is on grain or not. By increasing the fat and decreasing the carbohydrates in the diet, the horse's muscle is gradually "trained" to use more fat for energy than it normally would, decreasing its reliance on glycogen (animal starch). Most EPSM horses need at least 1 pound fat (2 cups oil or other fat source) per 1,000 pounds of horse per day. Increase this fat gradually, both to maintain your horse’s intestinal health and to help him accept the new diet.

One simple and effective dietary change has been to replace grain with an equal quantity of alfalfa pellets and gradually add vegetable oil until the horse is eating two cups of oil per day per 1,000 pounds of the horse's weight. Alfalfa pellets were selected only to act as a substance to mix the oil with. Although they are a good source of protein, calcium, and vitamin E, they are not a necessary component of the diet. Mixing a small amount of leafy alfalfa hay into the alfalfa/oil mixture may enhance palatability.

For horses that won't eat alfalfa pellets, try adding the vegetable oil to soaked beet pulp or one of the newer low starch and sugar feeds, of which many are now available. If your horse won’t tolerate a large volume of added oil, try providing part of the required fat from a commercial high-fat feed. I calculate the fat content only in feeds that are 10% or more fat, though. You can calculate pounds of fat from your feed by multiplying the pounds fed per day by the percentage of fat. That is, 1 pound of a 10% fat feed provides 1 x 0.10 = 0.10 pound of fat per day.

The vegetable oil may be derived from corn (the most expensive), soy, canola, safflower, coconut, etc., but avoid high levels of flax or linseed (more than 1 cup per day). At high levels (about 4 cups per 1,000 pounds of horse per day) flax oil can cause intestinal irritation, so I’d rather be safe than sorry. Your choice of oil depends on your preference, your horse’s preference, and your ability to find a cost-effective source. Buying vegetable oil in bulk from a discount store such as Costco or Sam’s Club, or from a restaurant supplier, will save you a lot of money. Five-gallon containers are the most economical.

Since an alfalfa-only diet is slightly low in zinc, add a vitamin-and-mineral supplement. Vitamin E supplementation is recommended at a level of 1 IU per day for each pound of the horse's weight. In selenium-deficient areas, selenium supplementation at 1 mg per 1,000 pounds of body weight per day is advised.

Although this diet may behigher in protein than other traditional equine diets, research proves that higher protein diets do not cause founder/tying up problems in horses. Nor do they damage the kidneys or liver. The horse may, in fact, use the added protein for energy and to rebuild damaged muscle.

Some horses will not eat alfalfa pellets, at least not in high volumes. For such horses, you might try mixing the pellets with Cocosoya from Uckele Animal Health, a blend of unprocessed coconut and soy oil that smells like caramel—horses like it, and it is naturally high in vitamin E. Another answer may be one of the lower carbohydrate commercial diets such as Purina Strategy, Nutrena Compete, Blue Seal Demand, Blue Seal Hunter, Blue Seal Racer, LMF low starch and sugar feeds, Nutrena Safe Choice, or any senior feed or other complete feed designed to replace hay if necessary. Now that nutritionists realize the many benefits to feeding less grain to horses, more and more low starch and sugar feeds are out there to choose from. With any of these commercial diets that are less than 10% fat, add the same amount of vegetable oil as you would with alfalfa pellets.

If your horse objects to the recommended amounts of oil, choose a higher-fat feed such as Kent Feed Omegatin (20% fat), Nutrena Empower (22% fat), or Buckeye Ultimate Finish (25% fat) and decrease the oil by the amount of fat fed from the feed (see calculation above). Many products now utilize rice bran as a fat supplement and can work well when added to oil. One example is Natural Glo (Wolcott Farms, 800-680-8254, ask for Pat Cassidy). But rice bran is only 20% fat, so you need five pounds of rice bran to provide the same amount of fat as two cups (one pound) of vegetable oil. Rice bran also contains some starches, which means the total diet will have less calories from fat. Use rice bran only when abbsolutly necessary and try to add oil or other 100% fat source as well.

Powdered animal or granular vegetable fat products are good sources of fat, provided they are designed for simple-stomached animal like horses and pigs, and not for ruminants like cattle and sheep. Effective fat sources for horses include Cool Calories (soy oil based) by Milk Specialties Company (toll-free 800-323-5424 extension 1156, ask for Catherine Gerardi), and the same company's less expensive Fat Pak 100 dry animal fat product. Buckeye Feed also markets a dry soy fat product called Ultimate Finish 100. If you are using a dry fat supplement, remember these products weigh half their volume, so 4 cups by volume of a dry fat equal 2 cups of oil.

The minimum caloric requirement per 900 to 1,000 pounds of horse is 10,000 to 12,000 calories per day, which goes up if the horse does heavy work. The high-fat EPSM diet provides approximately 16,000 calories per day. We are aiming to obtain 20% to 25% of dietary energy from vegetable oil. Since one cup of vegetable oil contains 2,000 calories, 2 cups of oil per day provides 4,000 calories, which is 20% to 25% of the daily requirement. If you want to reduce total daily calories to prevent excessice weight gain, try to cut down on pellets and hay before cutting down on fat. Just don’t decrease daily forage intake below 1% of the horse’s total body weight.

To avoid digestive problems, alfalfa pellets and all commercial rations should be initially mixed with the horse's previous ration and gradually increased as the former ration is decreased. The fat supplement should also be gradually increased until the recommended amount is reached.Increasing the oil by about 1/4 cup per feeding every few days usually work.

Horses with EPSM seem to be able to take in a tremendous amount of dietary fat following diet change, without a gain in weight. Once the muscle disease has apparently stabilized, however, the same amount of fat may result in increased weight. At this time, the amount of daily calories can be decreased, but try to keep fat levels as high as possible. If the EPSM horse is to survive, it must have fat added to its diet for the rest of its life.

Another advantage of fat supplementation for any horse is the fact that burning fats for energy is more efficient than burning carbohydrates, resulting in more energy and less body-heat production. Because fats are so calorie dense (they have more than twice the calories per volume of carbohydrates and proteins), you may feed smaller amounts of concentrates (grains), even to hard-working horses.


Beth A. Valentine, DVM, PhD, is involved with EPSM research and other veterinary matters at the College of Veterinary Medicine, Oregon State University. She developed these dietary recommendations in cooperation with Arleigh Reynolds, and they were reviewed by Drs. Kent Thompson and Harold Hintz of the College of Veterinary Medicine, Cornell University, Ithaca, New York. Dr. Valentine is this site's virtual vet and co-author of Draft Horses, an Owner's Manual.

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26 October 2011 last revision