Polysaccharide storage myopathy (PSSM) is a muscle disease that occurs in many different breeds of horse, though primarily in Quarter Horses, Paint Horses and Appaloosas. It’s a disorder characterized by abnormal accumulation of sugar stored in muscle (glycogen) as well as an abnormal form of sugar (polysaccharide) in muscle tissue. Horses with PSSM have up to 4 times the amount of muscle glycogen concentration as compared to normal horses.
There is a chance your horse has PSSM and you don’t even know it. In fact, horses with PSSM typically have calm dispositions and are in good body condition. Generally, PSSM symptoms are associated with tying-up: muscle stiffness, sweating and reluctance to move. What’s happening with PSSM is that the horse’s muscles are removing sugar from the bloodstream and transporting it into their muscles at a much faster rate than normal. They also produce more glycogen than normal horses. This extensive amount of glycogen concentration in the muscles is what causes the horse to tie-up more frequently and quicker than average.
While PSSM can’t be cured, it can be managed. There are several strategies involving rest, exercise and nutrition. Although it might seem like a good idea at first, allowing your horse to have prolonged rest after an episode appears to be counterproductive when dealing with PSSM. Instead, daily exercise is critical. Even 10 minutes a day has been shown to shown to be extremely valuable in reducing muscle damage. Once fit, some PSSM horses thrive with as little as 4 days of exercise as long as they receive daily turnout.
Feeding diets are also incredibly important for managing PSSM. When designing a feeding program for horses with PSSM, it’s important to limit energy sources containing high starch ingredients such as sweet feed, corn, wheat, oats, barley and molasses. High fat concentrates should be used as alternative energy sources in exercising horses.
With the right management, 75% of horses with PSSM stopped tying-up. Standlee’s nutritionists recommend feeding your horse Premium Western Alfalfa Compressed Bales, Alfalfa Pellets, Alfalfa Cubes and Alfalfa Chopped forage. Visit our website at standleeforage.com under nutritional resources to learn more about PSSM and what to feed to address tying-up or cramping.
This article was written by Tania Cubitt, PhD, Equine Nutrition & Reproduction, who works for Standlee Premium Western Forage.