Synchronous Diaphragmatic Flutter

Synchronous diaphragmatic flutter (SDF), more commonly known as “thumps,” is a condition characterized by hiccup-like contractions of the horse’s diaphragm. It is most commonly seen as a sign of dehydration and electrolyte depletion among horses performing in endurance races. SDF can also result from a horse ingesting cantharadin, a toxin found in blister beetles, insects that are sometimes harvested in alfalfa hay.