Do Horses Have A Gallbladder?

My family and I were watching a documentary about animal anatomy the other day, and how it differs from our own.

They talked about many animals, but horses came up more than once.

Something that was not mentioned was their gallbladders—which my son had just learned about in school.

He wasn’t letting it go and wanted to know if horses had one, so I decided to find out for him.

So, do horses have a gallbladder?

Horses do not have a gallbladder. It is relatively rare for mammals not to have a gallbladder, but there are many animals like horses which do not—including deer and some lamnoids like alpaca. A gallbladder is essentially an organ for storing the bile produced by the liver. Horses don’t need one because they eat constantly. 

So, though it is relatively rare for mammals, indeed vertebrates, not to have a gallbladder, horses are one of the few examples.

Our gallbladder, as I said, stores bile produced by the liver and processes it into fat for the body.

Humans only eat a few times a day, and eat foods with substantial calories.

Horses eat all day, so they don’t need one.

Let’s look at this further.

What is a gallbladder?

The gallbladder is a hollow, little organ in the digestive system.

The gallbladder, in most creatures including us, is used for the storage of bile.

Bile is a substance produced by the liver, so most animal gallbladders tend to sit directly next to the liver.

Our liver processes and metabolizes proteins and metabolites—breaking down many liquids we drink into means by which we can store it in our bodies.

This process produces bile, which is stored in the gallbladder.

Bile is released via a duct into the rest of the body where it aids in the digestion of fats.

So, your gallbladder is not a lot like your regular bladder—nothing is directly expelled from it out of your body.

Nonetheless, it serves a vital function.

Most mammalian gallbladders serve this function or a similar one—aiding in the digestion of fats as well as storing the substances needed to do.

So, with all that in mind, how do horses get on without one?

Why don’t horses have a gallbladder?

The simple answer is because they are always eating.

For us, and other animals, bile needs somewhere to be stored because this is how we get energy from food.

We eat large amounts of calorie rich food, and the energy and fat is stored in the rest of our body—gallbladders help regulate how much of it gets to certain parts of us.

Horses’ digestive systems function in a very different way.

They are huge, muscular animals, and given that most of what they eat is grass and hay, they have to spend a great deal of time eating.

In fact, they almost never stop.

So, the fats are just being constantly released into the rest of their body.

There’s no need to store the bile produced by the liver.

It’s in pretty much constant use.

How do they compensate, biologically, for this lack of an essential digestive organ?

Read on to find out.

How do horses compensate for not having a gallbladder?

Again, the simple answer is just by constantly eating.

There’s no need to store bile if the digestive system is in constant motion.

Horses instead have what is called a biliary system.

Our gallbladder could, equally, be called a biliary system, but a horse’s is very different.

All it really does is transport bile directly from the liver into the small intestines, where it breaks down the fats in it.

This is in more or less constant motion, as it eats. So, there’s no need for it to be stored anywhere.

This is really the fundamental difference: most animals don’t constantly graze but get calorie-rich foods occasionally.

There’s no need to store bile if you are constantly using it to digest food.

Do horses ever stop eating?

Obviously, they have to stop sometimes.

Left to their own devices, though, 99% of what they will really do is just eating.

They don’t really stop unless to move to another patch of grass.

Again, if you’ve ever seen a horse, you know that they’re enormous animals.

Maintaining that weight on a herbivorous diet is hard enough without the strength of an elephant to pull down trees.

Horses have to seem as though they’re constantly eating because anything less wouldn’t get them enough nutrients.

So, unless you want to spend all your days eating grass, you should be very thankful for your gallbladder.

Without it, we’d have to graze like horses do, and never stop eating.

This is clearly quite easy for them, but for us it would be a pretty big problem.

In any case, horses do not need one, and are rare as vertebrates for not doing so.

Indeed, many other grazers do have gallbladders.