Question
I have a nine-year-old Quarter Horse gelding that weighs about 900 lb (410 kg). He’s moderately fleshy, so it would be best if he lost some weight. He has been diagnosed with polysaccharide storage myopathy (PSSM), and he suffers from tying-up episodes during stressful times, generally when he is moved to a different stable. He’s fed three flakes of Bermudagrass hay and one flake of orchardgrass hay three times a day. He gets a vitamin and mineral supplement, a probiotic, and a hoof supplement, and I mix those with about 2 lb (0.9 kg) of grass pellets and 8 oz (1 cup; 240 ml) of wheat germ oil per day. Salt is available whenever he chooses. He has no pasture to graze. He spends a few hours each day in a sandy paddock; otherwise he’s in his stall. My vet had recommended a vitamin E product, too, but it’s hard to comb through the options. I’d like to give him the best possible diet to help manage his muscle problem.
Answer
Although you are on the right track with his current diet, I have a few additional recommendations to help with his recovery and perhaps lower the risk of future episodes.
The ideal diet for a horse with PSSM is one low in starch and sugar (nonstructural carbohydrates, known as NSC) and high in fat and fiber. There are several ways to go about achieving this kind of diet while providing necessary vitamins and minerals.
First, I do have a few questions about his hay. When you moved him from one barn to another, did you bring old hay with you or did you switch to new hay? Grass hay can vary quite a bit in NSC, which could provoke PSSM. For example, Bermudagrass hay has a NSC range of 9-17%. If he was getting Bermudagrass with 12% NSC and then switched to something closer to 17%, this could have some effect. The only way to know the exact NSC content of hay is to get it tested. If this is not possible, you may consider soaking it for 15-30 minutes to reduce water-soluble carbohydrates (sugar content).
Your horse is eating a lot of forage for his size. Assuming each flake of hay weighs about 2.5 lb (1.1 kg), he receives approximately 30 lb (14 kg) of hay daily, or about 3% of his body weight. On top of that, he also receives the hay pellets. A reasonable intake target to encourage weight loss for this gelding might be 2% of body weight each day in hay, or 18 lb (7.2 kg). If you’re worried about him having something to munch on much of the day, consider feeding his hay in a slow-feed haynet. These haynets are distinguishable from traditional nets by the size of their holes. Slow-feed haynets have much smaller holes, which makes the horse pick at the forage rather than grabbing large mouthfuls as once.
Reconsider the use of wheat germ oil. Though it’s likely helping the quality of his coat, the oil is adding unnecessary calories to his diet.
As you mentioned, there are several forms of vitamin E available to horse owners. Natural-source vitamin E (d-alpha-tocopherol) is the clear winner when compared to synthetic (dl-alpha-tocopherol), in terms of usefulness. The bioavailability and absorption rate of natural-source vitamin E is five times that of synthetic vitamin E. Investing in a liquid natural-source vitamin E like Nano•E will ensure your horse is getting the proper antioxidant support for muscle repair.
Your gelding might also benefit from the slow-release electrolyte Restore SR. Replenishing electrolytes in PSSM horses is a good way to promote proper muscle contractions and hydration. The slow release of sodium allows sustained absorption for maximum benefit.
A concentrate with decreased starch and high levels of fat and fermentable fiber, such as RE•LEVE, often results in significant improvement in horses with PSSM and other muscle disorders. Read the research.
Consistent exercise is important for horses with PSSM. Consider allowing him more access to the paddock. In addition, daily exercise is encouraged. Daily work should help improve his fitness and minimize the risk of tying-up episodes at shows or trail rides.
