tendon; thumps

Livestock production: Beware of thumps in horses

Unseasonably hot weather can mean a greater number of thumps cases in endurance horses.

Synchronous Diaphragmatic Flutter or thumps is one of the most common metabolic conditions in equine endurance rides.

It is seen more commonly in hot, humid conditions, and an unbalanced diet with the incorrect salt and electrolyte balance has also been implicated.

Sweating is a vital part of cooling down an exercising endurance horse. A horse exercising in high heat and humidity could lose more than 15 litres an hour in an attempt to cool itself down.

Sweat contains electrolytes and salts, and losses during a strenuous ride may cause blood levels of substances such as calcium and magnesium to drop severely.

A low blood calcium level causes the nerve running over the heart (that supplies the diaphragm) to become irritable and start to cause muscle contraction at the same rate as the heartbeat. The horse begins to develop a rhythmic twitching of the flanks in time with the heartbeat, often seen on one side only.

This can progress to severe contractions of the diaphragm – almost like a hiccup. The sudden contraction of the diaphragm may cause a drum-like sound – hence the name thumps.

The condition isn’t life threatening, but it does indicate the beginning of major metabolic changes in the horse. Stop exercise immediately and consult a veterinarian for treatment.


  • Treatment involves stopping exercise, cooling and rehydrating the horse.
  • The veterinarian may give injections containing calcium and magnesium into the vein or as part of a drip.
  • Thankfully, the condition normally responds quickly to treatment.

Consulting a qualified equine nutritionist with expertise in endurance diets will help formulate a balanced preventative diet.

Never use the bicarbonate-based electrolytes designed for race horses in endurance horses. Endurance horses have a totally different blood acidity and energy metabolism, and bicarbonate may actually cause thumps in an endurance horse.

Also read: What is strangles in your horses and how to treat it?

  • This article was written by Dr. Marc Walton and first appeared in Farming SA.

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