Horse Health

The Gas They Pass (Hopefully)

©roam and shoot/Flickr CC by 2.0
©roam and shoot/Flickr CC by 2.0

So, I was reading an article on National Public Radio this morning. It was about the gas people pass. Farts. Really.

JOKE 1: What’s the sharpest thing in the world?

A fart. It goes through your pants, and doesn’t even leave a hole.

There are many reasons to love horses. At least one of them is comedic. And that reason is because horses fart.

So, when, exactly, do horses fart? Well, to borrow liberally from Elizabeth Barrett Browning, let me count the ways.

  • When breeding
  • When jumping
  • When running
  • When playing
  • When coughing
  • When standing
  • When eating

And I’m sure that I’ve missed plenty.

JOKE 2: An elderly couple go to church one Sunday. Halfway through the service, the wife leans over and whispers in her husband’s ear, “I’ve just let out a silent fart. What do you think I should do?”

The husband replies, “Put a new battery in your hearing aid.”

The digestive tract of the horse is very different from that of people. They belong to a group of plant-eating animals called hind gut fermenters (that is, they do their fermentation in the back parts of the digestive tract, farther away from the mouth).

horsedigestivesystem

Cows, alpacas, and yaks eat plants, too. But unlike other animals that eat plants, horses have a stomach with a single chamber (the single, simple stomach makes horses similar in some ways to people, dogs, and cats). The animals with digestive tracts most like horses include tapirs and rhinoceroses (it seems that they can also be rhinoceri, depending on your grammatical source).

Plant material is high in a very fibrous material called cellulose. It’s a material that simply can’t be digested in the simple stomachs of many animals. So horses—and many other herbivores—have devised a strategy. They breakdown the plant material in a process that all those who drink alcohol know well: fermentation (Read more about the digestive processes of the horse).

And guess what is one of the primary by-products of fermentation? Gas!

Horses (and other hind gut fermenters) digest their plant material after it goes through the stomach and small intestines. In fact, a good bit of the stuff that you feed your horse makes it through the stomach and small intestines essentially undigested. It’s when the food reaches the horse’s hind gut that the bacteria—or gut flora—go to work.

When the gut flora go to work, it not only breaks down the plant material, but it provides the horse with necessary vitamins, too (which, for you supplement enthusiasts, is why it is very difficult to make a horse’s diet deficient in most vitamins).

JOKE 3: At dinner party, a man farts. Other man says “How dare you fart in front of my wife.”

First man says “Sorry, I didn’t realize it was her turn.”

Fermenting at the back of the intestinal tract has some pluses and minuses. On the downside, digesting plant material before it gets to the stomach is generally considered more efficient, and, the fact is, cows digest plant material more efficiently than do horses. (That’s why horse poop has bigger hay particles in it than does a cow patty).

However, animals that ferment after the food goes through the stomach can eat small amounts of relatively poor quality feed all day long, and can thus survive in conditions that might not work so well for cows (and other foregut fermenters). And horses get a lot of nutrition out of relatively small quantities of feed. In the wild, horses are on the move and eating constantly, taking advantage of the growing phases in different areas, and they can eat a lot more, too.

A NOTE ABOUT FERMENTATION: Fermentation has been used, and celebrated, for a long, long time. It’s been used in beverages since Neolithic times, and it’s been documented in China, Georgia, Egypt, Babylon, and Mexico (among others) since early in the BC era. Fermented beverages have religious significance in Christianity and Judaism, and there was even a Baltic god of fermentation. (Ragutis, if you have to know).

Since animals that ferment in the hind gut can eat more, and they can process their food more rapidly, than cows and other foregut fermenters, they can grow bigger. In fact, the largest herbivores, both living and extinct (elephants and indricotheres, a type of rhinoceros), have fermented their feed in the hind gut. And, presumably, they’ve farted a lot, too. I don’t know, I’m just passing it along.

rummy
One of my rabbits, Rummy, fermenting her romaine. ©Dr. David Ramey

But not even all hind gut fermenters are the same. Some, mostly larger species, like horses (and rhino), ferment primarily in the colon. Others—mostly cute little critters like bunnies (or rodents, which, admittedly, are polarizing when it comes to opinions about cuteness)—ferment mostly in the cecum, a dead end sac that is like our appendix, only lots bigger. Animals that ferment mostly in the colon tend to have bigger colons (proportionally) than do the little guys.

BAD PICKUP LINES

Did you fart? ‘Cuz you just blew me away!
Mind if I hang out here until it’s safe back where I farted?
Hey, somebody farted! Let’s get out of here.

So what does all this mean for your horse? Well, several things.

  • Your horse probably doesn’t need vitamins. The bacteria in the horse’s gut mean that your horse gets most all of the vitamins that he’ll ever need. In fact, it’s almost impossible to make a horse vitamin deficient, with the exception of vitamin E. And, if your horse eats most anything green, or gets some sort of a fortified grain (most are), you probably won’t have to worry about that, either.
  • Gas, a by-product of fermentation, has to leave the system somewhere. In cows, where fermentation goes on before the stomach, it comes out the mouth. Cows burp a lot. In horses, it comes out the back. Horses fart a lot. With rhinos, I can only imagine.
  • Since horses ferment in the colon, and horses have a long colon, there’s potential for trouble. If stuff isn’t passing through the gut, gas can build up. In addition, since the colon is so long, it can twist and turn on itself, especially if it’s full of gas or feed. And that causes colic, which is the number one medical problem of the horse.

So next time you (or a small child) find yourself giggling uncontrollably at your horse playfully bucking and farting around the ring or pasture, at least you know why it’s happening. In fact, people have been laughing at farting horses for a long time.

The Japanese scroll entitled He-Gassen (Fart Battle) dates from the Edo period, making it somewhere between 200 and 400 years old.
The Japanese scroll entitled He-Gassen (Fart Battle) dates from the Edo period, making it somewhere between 200 and 400 years old.

And a little knowledge CERTAINLY doesn’t make it any less funny.


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About the Author

Dr. David Ramey is a 1983 graduate of the Colorado State University School of Veterinary Medicine. In addition to being a full-time equine veterinary practitioner in Encino, California, Dr. Ramey is also an internationally recognized author, lecturer and blogger. Dr. Ramey is a vocal advocate for the application of science to medicine, and—as such—for the welfare of the horse.

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