Feeding the “Polysaccharide Storage Myopathy” Horse

Horse laying down

Since Polysaccharide Storage Myopathy involves the deposition of a non-bioavailable form of glycogen into the muscle tissue, the best diet is one that minimizes glycogen formation. If the horse needs a calorie source in addition to the cellulose provided by pasture hay to maintain body condition score a good source of calories would be vegetable oil or sugar beet pulp.

Vegetable oil is converted to “energy dense” volatile fatty acids in the hindgut, and bypasses glucose metabolism. An adult horse of average weight can be given as much as 1 cup (240 ml) three times per day if needed to maintain weight; however this amount of oil must be gradually increased from one third cup (80 ml) per feeding.

Sugar beet pulp is another low glycemic index feedstuff that when digested by the hindgut microbes will provide a safe calorie source. Sugar beet pulp is the product that is remaining after the sugar has been extracted. Sugar beet pulp is a high cellulose feeding stuff for horses. The cellulose is converted to usable energy in the hindgut of the horse and therefore bypasses sugar and glycogen formation.

Low carbohydrate and low glycemic index feedstuffs combined with frequent small meals is the best feeding program for horses with Polysaccharide Storage Myopathy.

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J. Frank Gravlee, DVM, MS, CNS
Scott Gravlee, DVM, CNS
Equine Nutrition Consultants
Life Data Labs, Inc.