HIGH FAT, LOW CARBOHYDRATE DIET FOR EQUINE POLYSACCHARIDE STORAGE MYOPATHY
DEVELOPED BY DRS. ARLEIGH REYNOLDS AND BETH VALENTINE

Reviewed by Drs. Kent Thompson and Harold Hintz

Caloric requirement of a 900-1000 lb horse is a minimum of 10,000-12,000 calories/day (would increase with heavy work - this diet will provide ~16,000 calories/day)

The average equine diet provides ~4-7% of total daily calories from fat. We are aiming to obtain ~20-25% of dietary energy from vegetable oil; 1 cup of vegetable oil = '2000 calories.

Therefore, 2 cups oil/day = ~4000 calories, which is ~20-25% of daily requirement. Alternativdy: could feed an equivalent amount (16 oz) of a fat supplement such as Vita Flex Fuel Formula (228 calories/ounce) or Fat Pak 100 (Milk Specialty Products, 800 323 4274 ext 1157, ask for Kathy Fleck); rice bran can be fed to supply needed fat, but will require 5 times the volume of vegetable oil or powdered fat.

Potential nutritional deficiencies in a no grain, high fat diet:

  1. Protein: As the amount of hay fed may be decreased to both decrease caloric intake and decrease dietary carbohydrate, a dietary deficiency of protein is possible, and EPSM horses may require a higher level of protein to rebuild and maintain muscle mass.

    Therefore, alfalfa hay is recommended, along with a small amount of alfalfa pellets to mix with oil and supplements. Alternatively, could feed ~5 lb of alfalfa pellets, and 13 (or less) pounds of timothy hay. Commercial diets such as Purina Athlete and Strategy provided needed protein, Natural GIo does not.

  2. Sodium: Ensure that a salt block is available, or add salt to oil-pellets mixture to increase palatability.
  3. Calcium: Requirement should be met by alfalfa hay/pellets, or a commercial diet.
  4. Phosphorus: Will be present in hay and green grass - to date we have not seen any problems with phosphorus levels.
  5. Vitamin E/selenium: Recommend daily supplement to provide at least 1000 Units of vitamin E/day and 1 mg selenium/day (this is recommended for all horses, regardless of diet, especially in selenium-deficient areas).

Comments:

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 pellet/oil mixture may enhance palatability. For horses that won't eat alfalfa pellets, either a commercial high fat feed (see below), or addition of vegetable oil to drinking water, can ensure that the horse is getting enough daily dietary fat. There should be no difference between vegetable, corn, or canola oil; avoid flax or linseed oil in these high quantities.

Hay requirement, as well as total grain substitute (including vegetable oil) requirement, may be adjusted according to weight gain or loss, and both can be decreased if horse is on good quality pasture. A supplemental vitamin/mineral mix can also be fed according to manufacturer's recommendations.

THE IMPORTANT THING IS TO AVOID CARBOHYDRATES IN THE DIET, AND TO PROVIDE FAT AS AN ENERGY SOURCE! EPSM HORSES REQUIRE DIETARY FAT ON A DAILY BASIS, EVEN WHEN YOU MIGHT HAVE DECREASED THE AMOUNT OF GRAIN FED!

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 dietary fat can be decreased, but not eliminated.

IT IS VITALLY IMPORTANT TO REALIZE THAT, IF YOUR HORSE RESPONDS TO DIET CHANGE, THAT DIET SHOULD BE MAINTAINED FOR THE LIFE OF THE HORSE.

Final diets are summarized below. They include both alfalfa pellet/vegetable oil diets as well as substitutes using currently available commercial diets (unless total calories are indicated, amounts are given for maintenance of a 1000 lb horse, to be adjusted up or down as necessary):


EPSM DIETS

Diet I (per day)

5 lbs alfalfa pellets
13 pounds timothy or other grass hay
16 oz vegetable oil (or Fuel Formula or Fat Pak 100)
Vitamin E/selenium supplement
Trace mineral salt block

Diet 2 (per day)
(Have also had success with Blue Seal high fat diets - Vintage Gold & Vintage Racer & Demand - with added vegetable oil.)

4 oz alfalfa pellets
8-10 lbs alfalfa hay
16 oz Fuel Formula or Fat Pak 100
Vitamin E/selenium supplement
Trace mineral salt block

Diet 3 (per day)

2-3 lbs Purina Athlete (14% protein, 14% fat)
1/2 -2/3 cup vegetable oil (or 5-6 oz powdered fat)
13 pounds timothy or other grass hay
Vitamin E/selenium supplement
Trace mineral salt block

Diet 4 (per day)

2 lbs Purina Athlete
1/2-2/3 cup vegetable oil (or 5-6 oz Fuel Formula or Fat Pak 100)
8-10 lbs alfalfa hay
Vitamin E/selenium supplement
Trace mineral salt block

Diet 5 (per day)

3-5 lbs Natural Glo (Wolcott Farms, 1 800 680 8254, ask for Pat Cassidy). This diet is 20% fat, and therefore no added fat supplementation is necessary, except perhaps for severe cases. (Best if mixed with alfalfa pellets, Purina Athlete or Strategy)
8-10 pounds alfalfa hay
(Timothy hay not advised due to low protein and calcium content of Natural Glo)
Vitamin E/selenium supplement
Trace mineral salt block

Diet 6 (per day)

6 lbs Purina Strategy* (14% protein, 6% fat)
1.5-2 cups of vegetable oil (or 12-16 oz powdered fat)
8-10 lbs (alfalfa) or 13 pounds (grass) hay
Vitamin E/selenium supplement
Trace mineral salt block
Note: Nutrena Compete is similar to Strategy

Diet 7 (per day) - provides 24,000 calories/day, for racing horses and large draft horses

7 lbs Purina Strategy
3 lbs Purina Athlete
1/2-3/4 cup vegetable oil or 1-1.5 lbs rice bran
10 lbs alfalfa hay
Vitamin E/selenium supplement
Trace mineral salt block

Notes on these diets:

Although the commercial diets (Natural G!o, Purina Stategy, and Purina Athlete) provide a dietary source of selenium, supplementation of selenium at 1 mg/day is still recommended, and is well within the safety limit for dietary selenium in horses.

Alfalfa pellets and all commercial diets should be initially mixed with the horse's previous grain, with gradual decrease in the amount of grain, increase in the amount of alfalfa pellets or high-fat commercial diet, and gradual increase in the amount of fat supplementation.

Purina Stategy and Wolcott Farms Natural Glo seem to be more palatable to many horses than is Purina Athlete.

Some calorie information:
Alfalfa pellets (and alfalfa hay) = approximately 900-1000 calories/Ib
Purina Strategy = 1500 calories/Ib
Purina Athlete = 1900 calories/Ib

Dr. Beth A. Valentine
Oregon State University
Dept. of Biomedical Sciences
College of Veterinary Medicine
Magruder 142
Corvallis, OR  97331
e-mail: Beth.Valentine@oregonstate.edu


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