Skip to content
Search Library
thumbnail

A horse with thumps looks alarmingly like a human with hiccups. In horses, spasms of the diaphragm cause marked, and sometimes convulsive, twitching of the flanks that mirror heartbeat. Though hiccups can be caused by any number of reasons in humans, the origin of thumps in horses can usually be traced to electrolyte imbalance.

Also called synchronous diaphragmatic flutter, thumps is generally observed in fatigued horses, especially those that have sweated profusely during a bout of prolonged exercise. In severe cases, convulsions are so extreme that a thumping noise is produced, hence the name.

Body-wide electrolyte imbalance causes certain physiological peculiarities, one of which is thumps. “The imbalance may occur because the horse loses large quantities of certain minerals, namely calcium, chloride, magnesium, and potassium, through extensive sweating or severe diarrhea, or because there is a problem with the way minerals are used within the body, such as kidney or parathyroid gland dysfunction,” said Kathleen Crandell, Ph.D., equine nutritionist with Kentucky Equine Research (KER).

Horses that are fed a diet high in calcium, such as alfalfa, may be more prone to developing thumps during an endurance competition because the excess calcium in the body affects its ability to mobilize calcium to counteract losses during extended exercise.

The phrenic nerve controls movement of the diaphragm, the muscular sheet that separates the chest and abdominal cavities. Alkalosis resulting in low ionized blood calcium causes the phrenic nerve to become hyperexcited, spurring diaphragmatic contraction. Because the nerve runs over the right atrium of the heart, the excitability synchronizes diaphragmatic contraction with heartbeat.

“Treatment of thumps consists of electrolyte replenishment, and if severe enough parenteral administration of calcium. Prevention depends upon maintaining electrolyte balance during endurance exercise,” said Crandell.

Routine electrolyte supplementation remains the best way to keep thumps from occurring. When significant electrolyte losses are anticipated, such as during an endurance ride or drive, electrolyte supplementation before, during, and after the ride is advised. For horses that have a diet high in calcium, it may be advisable to decrease the amount of calcium, if not chronically, then for at least a few days before the competition to stimulate normal calcium homeostasis.

“Electrolyte losses go hand-in-hand with sweat production; if a horse sweats a lot during endurance work of one type or another, supplementation is warranted. If, conversely, a horse exerts little athletic output and thereby sweats minimally, few electrolytes will be lost and supplementation requirements will be lower,” advised Crandell.

A well-formulated electrolyte such as Restore SR and Restore Paste (Endura-Max and Endura-Max Paste in Australia) delivers key electrolytes to horses, a necessary management strategy to avoid thumps.

Electrolyte supplementation is just one component of a well-rounded diet for horses engaged in any endurance activity. Other nutritional tweaks might be necessary to achieve the best performance. Would you like to talk to an equine nutritionist? Start the conversation now.

X

Subscribe to Equinews and get the latest equine nutrition and health news delivered to your inbox. Sign up for free now!