EPSM Diet Goals
by Beth A. Valentine, DVM, PhD
The goal of this diet is to provide no more than 15% total daily calories from starch and sugar, and at least 25% of total daily calories from fat. Such a diet is essential for the well-being of a horse with EPSM (equine polysaccharide storage myopathy), but is beneficial for all working horses. Feeding fat may seem unnatural, but then the Natural Horse doesn't eat grain, either. The ancestral horse was a far cry from today's working horse in size and build, and was not a working horse. Only recently have we begun to understand how best to feed working muscle.

Either grass or legume hay may be fed to a working horse. Even alfalfa hay is fine, as it does not have a high enough starch content to cause concern. Avoid grain hays, such as oat hay and barley hay with remaining seed heads.

Provided the horse gets no less than 1% of its body weight in forage per day, the exact amount is not critical and can vary, depending on whether the horse needs to gain or lose weight. Lush spring pasture is higher in starch and sugar than summer grass, necessitating a higher amount of dietary fat during this time.

Vitamins and Minerals
  • Vitamin E. All horses should get least 1 IU vitamin E per pound of horse per day. Vitamin E is especially important for horses not on alfalfa products or green grass for much of the year. You cannot hurt a horse with extra vitamin E.
  • Selenium. In areas that are selenium deficient horses need 1 to 2 mg selenium per 1,000 pounds of horse per day. Selenium can be toxic at high levels, though, so be aware of all sources of selenium in your horse's diet. If you have any doubts of selenium deficiency or excess ask your veterinarian to blood test for selenium levels.
  • Broad spectrum vitamins and minerals. Horses on a fat supplemented diet often will not eat the manufacturers' recommended amounts of fortified commercial concentrated feeds per day. If forage quality is good, most vitamins and minerals will be adequately supplied by the forage. Horses on lesser quality forage, hard working horses, breeding horses, and growing horses need a daily vitamin and mineral supplement.
  • Other supplements. Hoof supplements, joint supplements, and the like are fine to include in any horse's diet.

Avoid treats containing grain or sugar. Most EPSM horses have no problems when fed carrots and apples in moderation. My horses like Kellogg's Cracklin' Oat Bran, which has about 20% calories from fat.

EPSM horses need at least 1 pound of fat per 1,000 pounds of horse per day. Start with small amounts, such as 1/4 cup of oil per feeding, and increase by about 1/4 cup every few days. Use the general rule that 2 cups of oil equal 1 pint, equals l pound.

To get a horse to start eating the right amount of oil sometimes requires adding a small amount of something sweet, such as molasses, carrots and apples, apple juice, peppermint flavoring, or a handful of oats or sweet feed. Aim to later decrease or eliminate this small amount of starch and sugar.

No equine feed is currently high enough in fat to provide the proper calorie ratios to EPSM horses without an additional fat source. Use the least amount of feed in the bucket that gets the horse to eat the maximum amount of daily fat while maintaining good weight. In general, aim to feed no more than 6 pounds of any feed, other than a pure forage based feed, per 1,000 pounds of horse per day.

Low Starch, Low Sugar Feeds
Look for feeds with no more than 33% starch and sugar. In general, the higher the protein and fat, the lower will be the starch and sugar. Ingredients such as soy hulls, beet pulp, bran, wheat bran, and wheat middlings are relatively low in starch and sugar. Good low starch, low sugar feeds include alfalfa pellets, other hay pellets, alfalfa cubes (soaked in water when oil is to be added), low molasses content beet pulp (soaked in water), complete feeds that are meant to replace hay if needed, dengie or chaff products, and chopped hay products.

Higher Fat Feeds
If a feed is 10% or more fat you can use the feed to provide some of the needed fat. No feed to date, with the possible exception of Kent Feed Omegatin (20% fat and only 13% starch and sugar) is high enough in fat and low enough in starch and sugar to provide an EPSM diet without some added 100% fat. Ultimate Finish at 25% fat, for example, may be fed using the basic proportion of 3 pounds Ultimate Finish with 1⁄2 cup added oil per 1,000 pounds of horse per day.

Anything else you add to the concentrated portion of your horse’s diet will dilute the fat calories. Most companies making these feeds suggest using them only as a supplement to other feed. For EPSM and hard working horses, however, these products should be fed alone, along with good quality forage or a daily vitamin and mineral supplement. Some examples of high fat feeds rare: Kent Feeds Omegatin (20% fat), Nutrena Empower (22% fat), Moorglo (15% fat), Rice bran, powdered (20% fat), Buckeye Ultimate Finish (25% fat), and Re-Leve (about 10% fat). Please note: Purina Athlete is too high in starch and sugar (almost 50%) to be a good EPSM feed.

Calculate amounts of fat fed from these products by multiplying pounds fed per day by the percentage of fat. For example, 3 pounds of Ultimate Finish contain 3 times 0.25 = 0.75 pounds of fat.

Feeds containing 20% or more fat may be supplemented with rice bran (20% fat) for additional fat. All other feeds require the addition of a 100% fat source.

100% Fat Supplements
Any vegetable oil you would put in your salad‹such as soy, canola, corn, safflower, or cottonseed‹is suitable for horses. Cocosoya and wheat germ oil are also fine, just more expensive. Other good sources of fat are Cool Calories vegetable oil products by Milk Specialties (toll-free 800-323-5424 extension 1156, ask for Catherine Gerardi), as well as the same company's less expensive Fat Pak 100 dry animal fat product.

Please give this information careful consideration and discuss it with your veterinarian. Neither I nor the folks at Rural Heritage have anything to gain by encouraging you to change your draft horses' to a high fat, high fiber, and low starch and low sugar diet, other than the desire to help you keep your draft horses productive, healthy, and happy for many years to come.

Beth A. Valentine, DVM, PhD, is a veterinary pathologist at Oregon State University in Corvallis and the author of Draft Horses, an Owner's Manual. these dietary guidelines with assistance from Dr. Harold (Skip) Hintz of Cornell University, Dr. Bob Van Saun of Pennsylvania State University, Don Kapper at Buckeye Feeds, and Kent Thompson previously at Purina Mills now with Buckeye Feeds. This article appeared in The Evener 2003 issue of Rural Heritage.

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26 October 2011 last revision