Equine Polysaccharide Storage Myopathy

 

EPSM (Equine Polysaccharide Storage Myopathy) is a muscle condition that results in an excessive buildup of glycogen in the muscle.  In the normal horse, glycogen is the energy source in muscle contraction.  An EPSM horse cannot complete this process, which results in the excess in stored glycogen.  This results in muscle cramps and weakness.

Obvious symptoms include tying up, reluctance to move, stiff gaits especially in the hindquarters, and sweating.  Less obvious signs of EPSM are reluctance to trot, back or canter, muscle atrophy and weakness, or lack of energy. This condition can be misdiagnosed as back or hock soreness or colic.  EPSM has now been documented in several horse breeds. 

Dr. Beth Valentine, College of Veterinary Medicine, Oregon State University has been instrumental in completing research on EPSM and assisting us with the best feeding program for these horses.  The result is the following feeding program.

The major source of glycogen in a horse’s diet is found in cereal grains (oats, corn, and barley).  In EPSM horses, energy must be provided by other sources.  These include; fiber found in hay or pasture, fatty acids from fats or oils, and amino acids from protein.

For EPSM horses we recommend free choice grass or mixed hay.  The necessary amino acids, minerals and vitamins are provided by feeding one pound of Gro’N Win̉ per 1000 pounds of body weight per day to all horses 3 years old and older for maintenance. All horses with EPSM need one pound of fat per one thousand pounds of body weight to maintain optimal muscle function. Each pound of the Ultimate Finish̉, a 25% fat, extruded (or fully cooked) product, provides ¼ pound of fat. Four ounces of corn oil (½ cup) also provides ¼ pound of fat. If the horse needs additional energy to maintain or increase body weight, the amount of Ultimate Finish̉fed can be increased. If the horse is overweight, we recommend increasing the horse’s daily activity and exercise. The following chart lists the amount to feed (in pounds) per DAY to horses that weigh 1000 pounds.

                                                                                                            Ultimate           Corn

Growing

6 months                         500                   8.0                  3.0                    1.50      +          ½ cup

12 months                       715                 11.5                  2.5                    1.75      +          ½ cup

18 months                       880                 13.0                  2.0                    2.00      +          ½ cup

24 months                       990                 14.0                  1.5                    2.50      +          ½ cup

 

Maintenance

36 months and older       1000                 18.0                  1.0                    3.00      +          ½ cup

 

Reproducing

Pregnant                       1000                 16.0                  2.0                    3.00      +          ½ cup

Nursing 1-3 mos.           1000                 25.0                  5.0                    4.50      +          ½ cup

Nursing 4-6 mos.           1000                 22.5                  3.0                    3.00      +          ½ cup

 

Training

Lay-ups                         1000                 18.0                  1.0                    3.00      +          ½ cup

Light                             1000                 22.5                  1.5                    3.00      +          ½ cup

Moderate                       1000                 26.0                  2.0                    3 to 4    +          ½ cup

 

All horses should have free choice:  Harvest Salt and Grass Plus Mineral & Vitamin Mix