Tying Up in Horses: Part 1 - Symptoms and Causes

TYING UP: Why I wrote my University dissertation on tying up and what happened to me:

Anyone who has had a horse ‘tie-up’ whether out competing or at home in training, will know how unpleasant for the horse, and worrying for the owner, this can be.

Having been so excited to qualify, I was absolutely gutted when my wonderful horse Casanova “tied up” (albeit mildly) half way round the cross-country phase in the under 18 National Championships. This tying up was the beginning of a three year project which became my university dissertation and I subsequently produced the largest scale study of its kind into tying up in sport horses. Casanova has never tied up since and has led a full-on competition life! (There have been many studies into racehorses).

These blogs focus on Recurrent Exertional Rhabdomyolysis (RER) and its causes - the most common type of tying up in Sports Horses.

Tying up or Azoturia has many names: Recurrent Exertional Rhabdomyolysis (RER), Polysaccharide Storage Myopathy (PSSM), Chronic Exertional Rhabdomyolysis and Sporadic Exertional Rhabdomyolysis to name a few.

What are the symptoms of tying up?

Stiffness in the hind quarters and/or a reluctance to move; black or very dark urine that has a distinctive smell. In extremely severe cases horses have been known to make very distressed noises. The reason why RER and PSSM are often put together is because they have the same symptoms but they are in fact different myopathies - different muscle diseases - see end of second blog.

What is the cause?

RER is most likely caused by the dysfunction of ion pumps in cell walls. Incorrect diet, electrolyte deficiency, irregular exercise programmes, letting a horse shiver, and high stress levels can all contribute to this, although how some of these interlink with ion pump dysfunction, is not yet fully understood. Through my own experiences and studies with mixed breed sport horses, I also concluded that the underlying gene causing this myopathy was recessive – must be carried by both parents - for the attacks to occur when triggered by external factors. All the sport horses that I have worked with that have suffered with this condition have thoroughbred in both sides of their pedigree (and are also crossed with other breeds).

For my recommendations for managing RER see my second blog.

Annie Forsyth gained a first class honours degree from the Royal Agricultural University Cirencester in 2014.