Polysaccharide storage myopathy causes painful muscle cramping in horses during exercise. Dietary management dramatically reduces episodes and improves welfare for affected horses.
PSSM causes acute painful episodes during exercise that significantly impair horse welfare. Horses experiencing tying-up show distress, reluctance to move, profuse sweating, and muscle pain that is often severe enough to prevent any movement. Without dietary management, PSSM horses experience recurring painful episodes throughout their working lives. The welfare improvement potential of dietary management is substantial: reducing starch and adding fat as an energy source dramatically reduces episode frequency in PSSM1 horses and enables many to work comfortably with appropriate management. The welfare failure is misattributing reluctance to work, stiffness, and behavioral changes to training problems rather than investigating underlying metabolic disease.