Tying up in horses

What is azoturia?

Azoturia /exertional rhabdomyolysis in horses, or ‘tying up' as it is more commonly known is a condition that causes painful muscle cramping in affected horses. Horses experience azoturia due to two main reasons: the horse has an underlying myopathy (muscle condition leading to chronic azoturia) or the horse has been over exerted physically (sporadic azoturia).

Who is predisposed to azoturia?

Any horse can get azoturia. Mares tie up more commonly than geldings or stallions and there can be a genetic /hereditary influence. Quarter horses, thoroughbreds and related breeds such as the Paint Horse or Appaloosa are more prone to polysaccharide storage myopathy, which is characterised by repeated episodes exertional rhabdomyolysis. In some cases this can be induced with very little exercise. Draft breeds such as Clydesdales, shires, haflingers, suffolks and fjords also get equine polysaccharide storage myopathy and they can get a second clinical syndrome that is characterised by progressive poor performance, a shivers-like gait, muscle wasting, muscle weakness, recumbency and death.

What happens when your horse gets an episode of azoturia?

If your horse ties up, he/she will become very painful and unwilling to move. They will probably sweat due to pain and anxiety and may stand on their tip toes on their hind feet as stretching the muscles of the hind legs to keep the feet flat to the floor is painful. The muscles in the gluteal area and hamstring area of the horse are often hard and painful to the touch and the horse will have an increased respiratory and heart rate. Azoturia can be mistaken for colic as severe cases can lead to the horse lying down.

What to do if your horse gets azoturia?

Move the horse as little as possible. If you are out riding away from your horses stable when they tie up, telephone for help. The horse should then be transported via lorry or trailer back to their stable to limit any further amount of muscle damage. Once the horse is in a stable, keep them warm with plenty of rugs, if the horse is sweating remember to change the wet rugs as required. Then call for the vet.

What will we do?

We will give your horse a full physical examination and then make them more comfortable by giving anti-inflammatories and pain relief.  If your horse is dehydrated, we will give them some fluids. This ensures that the kidneys do not become damaged due to the breakdown products from muscle damage being filtered through them.  The following day, a blood sample should be taken. The horse should be box rested and given anti inflammatories until the results of the blood test are back.

What will the blood test tell us?

The blood test shows us the levels of three different muscle enzymes. These enzymes are released from inside muscle cells when they are damaged due to azoturia. Creatinine kinase (CK) is a sensitive indicator of muscle damage, with levels peaking after 4-6hrs. If muscle necrosis is not ongoing, these levels decline rapidly over the next 24-48hrs. Aspartate aminotransferase (AST) peaks at 12-24hrs and declines over the next 21 days. A second blood test after 21 days will allow us to check that the your horse has no further muscle damage and confirm that they are ready to start working again.  Myoglobin is also released and this can cause the urine to be brown or orange and can cause kidney damage if severe enough.

How can you prevent this happening again?

  • Horses that suffer from azoturia should be fed a high fat:low carbohydrate diet. There are many commercially prepared diets for especially designed for this. Adding corn oil to their diet (50ml twice daily) can also help.
  • Always make sure that your horse is warmed up properly before doing any hard work and then is always given a period of cool down, after the hard work.
  • Making sure the horse is exercised daily helps to prevent episodes of tying up. If the horse is off work for any period of time, ensure that they are brought back in to work very slowly.

What if my horse still ties up?

Some horses require further investigation into finding out why they are tying up. Further blood samples may be taken to check that your horse is not deficient in Vitamin E or selenium, as these are very important for normal muscle function. We may request a urine sample from your horse to check that there are no electrolyte abnormalities.

We may do an exercise test on your horse, to see if exercise causes unacceptable increases in their their CK levels. We can then take a muscle biopsy from the back of your horses hind leg. This may reveal the cause of your horse tying up. We can do this here at Oakhill. This will enable you to manage your horse correctly, therefore helping to prevent azoturia.

If you have any further questions, please contact a member of our team here at Oakhill. We are happy to help.

The picture shows the site for muscle biopsy.



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Tying up in horses