Morgan Murphy

Equine Exertional Rhabdomyolysis Syndrome (ERS) or Tying Up in Horses

Equine Exertional Rhabdomyolysis Syndrome (ERS), also known as azoturia or, more colloquially, “tying up”, is a condition that affects the muscles of the horse. It comes on extremely rapidly during exercise and essentially renders the horse unable to move.  The muscles over the hindquarters become rigid and hard and the horse will be reluctant to move forward, often taking the stance as if to urinate. In severe cases the horse may collapse. Typing up is very dangerous and requires urgent veterinary treatment.  Our guide to this frightening condition will help you to learn and quickly identify the symptoms, allowing you to seek urgent treatment should the need arise.

What is ERS?

Performance horses may be prone to tying up

It was previously thought that tying up was caused by overfeeding grains and not sufficiently cooling down the horse after exercise. However, in recent years it has been demonstrated that this is not the case. The condition only occurs when a horse is being exercised, therefore the majority of cases are seen in performance horses or TBs. It is thought that in many cases the condition is caused by electrolyte imbalance, and can be brought on by various factors such as stress, oestrus or insufficient training.  Electrolytes are essential for proper muscle contraction and in cases where an imbalance occurs the muscle function can become impaired. 

In chronic cases of tying up, particularly found in Quarter horses, Appaloosas, Paints and Warmbloods, there may be an underlying condition known as polysaccharide storage myopathy (PSSM or EPSM). This is a condition characterized by the accumulation of glycogen (a form of carbohydrate) and an abnormal form of polysaccharide (a complex carbohydrate) in the muscle tissue. Horses with PSSM have increased ability to clear glucose from the blood, resulting in an increase in the rate of glycogen synthesis in their muscles. Glycogen concentrations in affected horses are 1.5 to four times greater than those in normal horses.

What Are Signs of Tying Up?

Tying up is very distinctive. It is important to recognize the signs as quickly as possible to prevent irreversible muscle damage and possible collapse. Symptoms include:

  • the horse being unwilling to move forwards. He may take small steps but will be extremely stiff;
  • rigidity of the hindquarter muscles, or the muscles becoming hot;
  • the horse becoming totally unable to move. He may fall down and be unable to stand;
  • a raised pulse and high fever;  
  • the horse adopting the urination stance without actually passing urine. In cases of severe muscle damage the urine may be red-brown owing to the presence of the broken-down myoglobin protein.

If you suspect your horse is suffering from an episode of tying up then you should stop exercising immediately. Cover the horse’s back, preferably with a blanket but your sweater or coat will suffice in an emergency, to keep the muscles warm. Offer water to the horse and call your veterinarian straight away. Avoid moving the horse before your veterinarian can see and treat him.

How is tying up treated?

Your veterinarian will confirm a diagnosis of tying up when tests reveal elevated levels of creatine kinase (CK) and aspartate aminotransferase (AST) in the blood, indicating damage to the muscle cells. Owing to the electrolyte imbalance the priority is to rehydrate the horse; the veterinarian may need to provide intravenous fluids in cases where oral rehydration will not be sufficient. Anti-inflammatories and corticosteroids can reduce pain, inflammation and further muscle damage. Hand walking is not recommended as although this was previously encouraged, to increase blood flow to the muscles, it has recently been shown to trigger further muscle damage in some cases.

How Can I Prevent Future Episodes Of Typing Up in my horse?

Without a definitive understanding of why the horse is tied up, it is impossible to prevent future episodes of tying up completely. However, there are a number of sensible precautions that can be taken to minimize the risk:

  • Always warm up and cool down effectively before and after any exercise.
  • Avoid over exertion and always build up a fitness program slowly. Do not push your horse to take part in an exercise for which he is not fit enough.
  • Minimize stress levels. If your horse is travelling to an event or needs to undergo any changes in routine try to do this slowly and, if required, introduce a calming supplement into his diet.
  • Keep the horse on a forage-based diet with low sugar; ensure that you cut down the grain component of the diet on days that he is not working. It may be necessary to completely eliminate grains. If so, the horse's weight can be maintained by adding oil to the diet such as a cup of corn oil.
  • Supplement horses with electrolytes after strenuous exercise, travel, breeding or hot weather.
  • Many veterinarians feel it is very important to supplement horses, suffering with tying up issues, with antioxidants in the diet – vitamin E and selenium have been shown to support healthy muscles.

Tying up is an extreme and dangerous condition in any horse, but by taking precautionary measures and appropriately gauging your horse’s fitness levels you may prevent future episodes of this painful condition.

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*Image courtesy of Dollar Photo Club