By Grant Jacobs 09/02/2019 2

You may have heard or read media outlets talking of cow farts.[1] This tweet from  University of California at Davis animal biotechnology/genomics scientist, Alison Van Eenennaam might help –

I’m sure I’ve been guilty of lazily using it.

Eructation is a very polite and fancy way of saying burp. As the dictionary puts it, “a belch”. (Yes, I check these things too!) It can also be called ructus or eruptus. I like eruptus. It resonates with the action so well.

But back on track. Methane emissions from bovines.

As Alison explains, bacteria in cattle break down cellulose in their rumens. Ruminants like cattle have four stomach compartments. A cow or cattle beast’s first stomach is called the rumen. The other parts are the reticulum, omasum and the abomasum.

Plants have a lot of cellulose. Mammals have very limited ability to break down cellulose on their own. Humans can’t digest cellulose,[2] for example. Grazing animals like cows, sheep and horses[3] have symbiotic bacteria to help them out.

You’d think that big, complex animals would have all the enzymes they need, but actually invisible-to-the-eye bacteria often do better than us. (It’s also one reason biosynthesis focuses on getting microbes to breakdown or create the things we can’t easily even in the lab.[4])

Symbiosis is where two different species live together in a way that both benefits. The bacteria in the cow’s rumen breaks down the cellulose that the cow can then eat. The cow gives the bacteria a place to live with plenty of food. They both help each other live.

Breaking down cellulose releases methane. The methane goes out the cow’s mouth. (I imagine this is particularly when they regurgitate the partly digested cud to their mouths to chew on it further.)

So. Not cow farts.

Methane and climate change[5]

Methane is a greenhouse gas – it contributes to global warming. It’s one of New Zealand’s larger contributions for greenhouse gases. Greenhouse gases are a major target in efforts to try restrain climate change. (Let’s face it, it’s already happening.)

There is research tackling bovine methane emissions from several different approaches, such as animal feeds, new breeds of cows/cattle, a vaccine, diet additives.

Other articles on Code for life

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Beatrice Tinsley, Cosmologist


I’ve mixed ‘cow’ and ‘cattle’ deliberately.

  1. New Zealand media seem to be doing better at this than they originally did. (I’m sure the Science Media Centre—who runs the forum that hosts this blog—had a hand in this.)
  2. This is part of what dieticians call ‘fibre’. It’s useful in a different way though, helping everything move through your gut well. Sufficient fibre in your diet may mitigate colon cancer to some extent.
  3. Horses are not ruminants. Horses are hindgut fermenters, with fermentation occurring in the large intestine and cecum. Like cows and sheep symbiotic bacteria break the cellulose down. Rodents, rabbits and koalas are also hindgut fermenters.
  4. There a lots of other reason, some are that you can grow them in vats, maintain ideal growth conditions, purify the products easily, and so on. You can think of the cow’s rumen as a biological vat, in some ways. Some animals and plants are used in biosynthesis too. The Ebola drug, Zmapp, is made in tobacco plants for example. A story for another day, perhaps.
  5. Climate change itself isn’t a topic I cover. Look to Hot Topic and elsewhere for more on that.

About the featured image

Cow (Swiss Braunvieh breed), below Fuorcla Sesvenna in the Engadin, Switzerland.

Image credit: Daniel Schwen. Source: Wikipedia, CC-ASA 3.0 unported.

2 Responses to “Not cow farts”

  • I’ve been advocating for more interest & R&D in NZ for biochar animal feed supplements to reduce methane. It has proven effective in published research. I’ve been harping about this for a few years from a v.small platform (AllBlackEarth – a current home for biochar related interest in NZ). You can find my harping by searching the website or related FB page.

    We hope to be preaching from higher ground soon with the formation of Biochar Network NZ (BNNZ) which had it IGM on 14Feb. (details at the website). Please do check out the science independently… try a search on ‘biochar’ & a keyword (animal feed, methane, …)

    • Just to be clear for readers re Trevor’s comment:

      There are quite a few different ways you might tackle reducing bovine methane emissions, diet additives being only one. I listed some briefly in the final sentence of the body text, “such as animal feeds, new breeds of cows/cattle, a vaccine, diet additives.”

      To state the obvious (!), my article is about the more basic issue of people calling these ‘cow farts’, not the different ways people might reduce the methane levels. That’s a much larger thing to take up, outside of my interest, and would take substantial time as I’d have to compare the different approaches, etc. I’m unlike to cover this.

      I’d encourage anyone interested in how it might be tackled to look wider than any one approach, and compare them. You’ll also need to consider the full greenhouse gas ‘costs’ of making and distributing the approaches, not just during the application itself, and to look critically at the evidence base for each. (You’ll may find that most are rather tentative.)