Study seeks to unravel genetic factors behind tying up in horses


A study in Britain aims to identify the genetic risk factors behind tying up in horses, with the hope it might lead to new therapeutic measures.

Evidence to date suggests there is a genetic component to many forms of the exercise-induced condition, but the gene or genes causing the disease have not yet been identified.

There is no known cure for the muscle-damaging condition, although many horses can continue to perform well if managed appropriately.

It is often recognised in racing Thoroughbreds, but a variety of other breeds can also be diagnosed with the condition.

The work is being carried out by researchers at the Royal Veterinary College in Britain, who will use samples from two sets of horses and ponies within a 40km (25-mile) radius of the college’s Hertfordshire campus.

Tying up is more formally known as recurrent exertional rhabdomyolysis (RER). It is most commonly known as tying up, but is sometimes called azoturia, setfast, monday-morning disease or just rhabdomyolysis.

The disease can be recognised by the clinical signs which vary in severity, but can include muscle spasms or muscle trembling, stiffness or hard muscles, high heart rate, sweating, muscle pain, reluctance to move or recumbency, red-brown urine (myoglobinuria) and in severe cases even death.

Often, a vet will confirm the diagnosis with a blood sample and sometimes also a muscle biopsy sample.

Scientists suspect that the severity of the clinical signs seen in cases might be associated with different specific genetic changes, and it is hoped that specific patterns of clinical signs can be identified in breeds that might be associated with some of these genetic changes.

Most relevant research so far has been done in Thoroughbreds, but the new study will look at other breeds popular in Britain, specifically warmblood horses and Connemara ponies.

The two sets of horses and ponies are sought for the study:

  • Warmblood horses and fully registered Connemara ponies over the age of 8 with no history of tying-up or other muscle-related diseases. These animals will be control subjects and they are an important part of the study.
  • Breeds as above, that have tied-up with exercise, at least twice – confirmed by blood testing by a vet.

A cheek swab will need to be taken for DNA testing, and owners will be asked to complete a questionnaire regarding each horse’s diet, exercise regime, breeding and clinical history in order to dissect genetic, lifestyle and environmental factors.

The results of this profile will be shared with each owner.

Horses in the study will have their personality profile assessed through the questionnaire.

The student researchers involved in the project are Victoria Lindsay and Kathleen Selhorst, supervised by Dr Androniki Psifidi and Professor Richard Piercy.

Those with horses and ponies within 40km of the Hertfordshire campus that may fulfill the requirements of the study are invited to email Victoria Lindsay if they are interested in taking part.

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