I have heard that if a horse needs to regurgitate that it is physically impossible and that the horse will die. Why is this so? (I believe it because I knew one that did die in such a way, but I don't understand the physiological reasons)

Thank you for any info on this curious topic.

dr.mlm

Horses have a band of muscle around the esophagus as it enters the stomach. This band operates in horses much as in humans: as a one-way valve. Food freely passes down the esophagus into the stomach as the valve relaxes but the valve squeezes down the opening and cuts off the passage for food going back up. Horses almost physically can't because of the power of the cut-off valve muscle. Also, the esophagus meets the stomach at an angle which enhances the cut-off function when the horse's stomach is bloated with food or gas. Then the stomach wall pushes against the valve, closing the esophagus even more completely from the stomach. Normally, the mechanics are such that the horse's stomach ruptures before the valve yields.

Thank you for the interesting explanation -- what an awful situation for a horse -- have they ever been known to regurgitate at all?

I have always heard that this is because horses lack a gall bladder.

As JerseyTomater said, the food in a horse's stomach is guarded by a strong set of sphincter muscles that allow food to enter, but not to return back to the esophagus, making vomiting a near impossibility. (These muscles stay sealed shut even after the animal has died).

Very rarely, it happens that food still in the esophagus (that has not yet reached the stomach) is regurgitated - but when this happens, it's more likely to exit through the horse's nose than mouth.

Yuk!

quote:

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Originally posted by JennX:
I have always heard that this is because horses lack a gall bladder.

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We have a complete lack of medical knowledge -- what does a gall bladder do for a horse??

Thanks for your info..