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 a disturbance of the horse’s typical muscle function. It is best compared to severe muscle cramp and it tends to happen during the early part of a horse’s exercise session.

When a horse suffers from azoturia, the muscle fibres break up and release muscle protein into the bloodstream. This is extremely painful so unsurprisingly the horse will be unwilling to move, may appear distressed and often sweats profusely. The affected muscles become stiff, swollen and painful to the touch, and the pulse and respiration rates rise. The horse may struggle to stale and the urine may be dark red/brown in colour.

The severity of an attack can range from mild stiffness and a shortened stride to total muscle seizure and even death. It occurs in horses and ponies of all types and ages and can appear at any stage in their life, while fillies and mares seem to be more prone than geldings.

If you suspect your horse may be suffering from azoturia you should keep him still, cover his loins and quarters with a rug or blanket and seek urgent veterinary advice. If the horse is at home move him quietly to his stable and allow him to lie down if he wishes. If out riding, the horse should be transported home in a horsebox or trailer.

There are many different disorders with multiple metabolic causes that come under the ERS umbrella. Many horses that suffer from tying up have an underlying tendency to develop the condition, which is then triggered by one or more factors, one of which is usually exercise. The difficulty is establishing the trigger factors as they vary from horse to horse.