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Tying Up/ Azoturia

Tying up /Azoturia is a broad term used to describe several different muscle disorders causing the breakdown of muscle fibres (rhabdomyolysis). Rhabdomyolysis can be divided into two groups;

  1. Exertional; whereby the damage occurs as a result of exercise
  2. Non-exertional; where the cause of muscle damage is unrelated to exercise, including Atypical myopathy, Immune mediated, post-anaesthetic, infectious and toxic.

Exertional muscle damage is either sporadic or recurrent. Sporadic rhabdomyolysis usually occurs when a horse is exercised over its current level of fitness most commonly affecting pleasure horses, whereas recurrent rhabdomyolysis is the result of a problem within the muscle itself and tends to affect racing thoroughbreds.

Clinical signs associated with sporadic exertional rhabdomyolysis include;

  • Stiffness
  • Reluctance to move
  • Pain on palpation of muscle, especially over hind quarters
  • Raised heart rate
  • Sweating
  • Muscle fasiculations
sweat up

Diagnosis of sporadic exertional rhabdomyolysis;

  • Clinical exam
  • Blood sample to measure CK and AST (muscle enzymes)

Treatment of sporadic rhabdomyolysis;

  • Rest
  • NSAID, such as phenylbutazone (bute)
  • Fluids


  • Maintain in regular work
  • Prevent box rest and allow access to pasture daily
  • Ensure horse is fit enough for intended use
  • Low sugar/starch and high fat/fibre diet

Feeding horses to prevent rhabdomyolysis;

  • Reduce starch/sugar in diet – remove cereals from diet as tying up occurs due to glycogen accumulation in muscle, so a diet high in fat/starch provides more sugar for glycogen production
  • If the energy needs of the horse can be met with forage alone i.e. the correct body condition score (BCS) and correct level of work can be maintained keep on forage alone
  • Do not turn on to rich fast growing pasture
  • If the horse requires additional feed to forage in order to maintain the BCS and level of exercise then add oil to feed, such as corn or soya oil
  • Provide the horse with 1.5-2% bodyweight of forage each day (7.5kg to 10kg for a 500kg horse)

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