Three facts about your horse’s spleen

Here's a quick look at the horse spleen, the organ responsible for much of a horse's athletic potential.

The next time you have an exhilarating gallop on your horse, thank his spleen. The horse spleen supplies the circulatory fuel for sudden bursts of speed. Here’s a closer look at this amazing organ.

A blurred photo of a horse galloping with a rider
When the spleen contracts, it pumps oxygen-bearing red blood cells into the bloodstream.

What it is: The horse spleen is a large, bluish-red, funnel-shaped organ with a sponge-like texture. It is wedged between the kidney and the small colon on the left side of the abdomen. When your horse is in a resting state, his spleen contains roughly one third of his trillions of red blood cells, also called erythrocytes. These red blood cells carry oxygen which muscular activity relies on.

What it does: The spleen contracts when prompted by chemicals called alpha agonists that are released during the flight or fight response, strenuous exercise and in response to various drugs. When it contracts, the organ pumps the oxygen-bearing red blood cells it holds into the bloodstream to enhance the horse’s aerobic capacity. This allows your horse to go from a stand still to a sustained gallop. The spleen also identifies and targets all useless or dangerous debris, saving many necessities of the circulatory system

Fast fact: A horse can live without the spleen. Other lymphatic organs, such as the liver, will take over essential tasks of the spleen. However, a horse without a spleen will be significantly less athletic then other horses.

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