Why Don't Horses Need a Gall Bladder?
By Juliet M. Getty, Ph.D.
Because horses are designed to eat constantly.
We humans, on the other hand, eat few, relatively large meals. Our gall bladder serves as a storage pouch for bile - the emulsifying agent produced by the liver that is needed to start fat digestion. When we eat a large amount of fat at one time, the gall bladder releases bile into the small intestine. If we did not have a gall bladder, and indulged in a high fat meal, we might experience indigestion.
Horses, on the other hand are trickle feeders - they are supposed to continuously graze on forage, all day and all night long (virtually all the time, with a few minutes of napping here and there). The small amount of fat that they eat is easily managed by the liver. Therefore, there is no need to store bile in large quantities.
In recent years, however, fat has been shown to be an alternative to high starch diets, since it is more concentrated in calories. There was initial concern that large amounts of fat would not be sufficiently digested. However, the horse's liver has the ability to compensate. This adaptation takes several weeks; therefore it is best to increase fat levels slowly.
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