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.
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.
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:
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.
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.
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:
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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