Essential Sugars

How genetic disorders GBED and PSSM can affect your American Quarter Horse.

From The American Quarter Horse Journal with contributions from Kristin Syverson

Given proper care and exercise, a horse with PSSM can go on to lead a productive life

At AQHA’s cloning forum Friday, March 6, Sharon Spier, an epidemiologist at the University of California-Davis discussed genetic disorders found in American Quarter Horses (order your copy of the"Cloning Forum" dvd if you missed it).

While HYPP has been a hot topic in the industry, disorders like GBED and PSSM have received less play, even though they are believed to affect a larger percentage of the Quarter Horse population.

GBED and PSSM are both related to glycogen storage in the body. Glycogen is a form of sugar stored by cells in our bodies to provide fuel and is essential in life.

Quick Facts: GBED

    • GBED is a glycogen branching enzyme deficiency.
    • An affected foal lacks the enzymes necessary to store glycogen. The brain, heart and skeletal muscles are unable to function, killing the foal.

Did you know that AQHA has 17 recognized horse colors? AQHA's Horse Color and Markings reference chart makes it easy to keep them all straight. Share this resource with your friends, or keep it to yourself and impress them!

    • GBED is always lethal in its homozygous form. Most affected foals are aborted or stillborn. Only the strongest survive to birth, and those will die within weeks. It is commonly dismissed as an accidental abortion or is misdiagnosed.
    • The baby has to inherit the gene from both parents.
    • When two carriers are bred, they will produce an affected foal about 25 percent of the time. Eight percent of Quarter Horses are carriers.

Quick Facts: PSSM

    • PSSM is short for polysaccharide storage myopathy.
    • A glycogen-storage disorder, PSSM causes the affected horse to store too much glycogen in the muscle, causing it to “tie up” or have stiff, painful muscles.
    • PSSM is an old mutation and possibly was an advantage to horses when conditions were harsh. However, for horses kept in modern conditions with good feed and little exercise, it causes problems.
    • It is a dominant trait, meaning that an affected horse will transmit the trait to 50 percent of its offspring, no matter who the affected horse is mated to. About 10 percent of Quarter Horses have PSSM.
    • Most cases of PSSM can be managed with proper attention to diet and exercise.

Download your copy of AQHA's Horse Color and Markings reference chart. It’s got a world of horse markings and color information packed into just one page, making it perfect for carrying in your pocket or storing in a glove box or folder.

Proper feeding and exercise regimens will help prevent PSSM episodes. Horses should be kept slim, and weight gain should be avoided. The diet should be low-starch and based on grass hay, avoiding alfalfa as much as possible.

Your horse can be tested:

University of Minnesota Neuromuscular Diagnostic Laboratory

University of California-Davis


Ongoing research on both diseases has been funded in part by the American Quarter Horse Foundation.

For more information, read the full article on both GBED and PSSM in the April 2008 American Quarter Horse Journal.

Show Where You Like to Ride and Win a Trip to QuarterFest

Wish you could share your favorite horseback riding spot with the world? Now you can in AQHA’s Life is a Ride video contest. That’s right; shoot a video of you and your horse at your favorite riding locale, and you could win some great prizes, including the grand prize trip to QuarterFest from Quarter Horse Outfitters!

AQHA’s inaugural QuarterFest ( celebration is May 1-3 in Murfreesboro, Tennessee, and 10 riders will be picked from submitted DVDs to receive VIP passes and tickets to the QuarterFest Extravaganza, which is scheduled for the evenings of Friday, May 1, and Saturday, May 2, in the Tennessee Miller Coliseum. The grand-prize winner also will receive a great Quarter Horse Outfitters prize package and the opportunity to participate in the Extravaganza.