Azoturia, which is more correctly described as equine rhabdomyolysis syndrome (ERS) and is also referred to as set-fast, tying-up and Monday morning disease, is best compared to severe muscle cramp and it tends to happen during the early part of a horse’s exercise session. It is extremely painful so unsurprisingly the horse will be unwilling to move. The severity of an attack can range from mild stiffness and a shortened stride to total muscle seizure and even death.