Kate Hore RNutr(Animal). Snr Nutritionist at NAF
Shivers is a slowly progressive, chronic neuromuscular disease in horses, typically showing itself in the gait when the horse is asked to back up, sometimes it is also visible as the muscles on rump and thigh as quivering or as flexing in the hind leg. It is almost exclusive found in larger breeds, such as draughts or warmbloods and geldings are 3 times more likely to be diagnosed as females are.
Generally, there are two types of Shivers; Hyperflexion and Hyperextension. Hyper flexion is where the limb is raised, like the animal is going to kick out, but will remain suspended and frequently shaking for a short period. Hyper extension is where the hind limbs move back further when backing up, making the horse stand like a saw horse.
Unfortunately, as a progressive disorder, there can be muscle atrophy, particularly over the back end, and some horses will fall when asleep, leading to injury of the fore limbs. Whilst there is no known treatment for the disorder, some cases do improve with plenty of turnout and exercise. If the horse suffers from both ESPM and Shivers, then an ESPM friendly diet may also help.