Cow dung plus antibiotics equals ultimate ozone killer

25 May 2016

Scientists analysing the dung of cattle treated with antibiotics (someone has to do it) have come across the startling reality that it doubles the methane output of typical cow dung, making it an awful lot worse for the environment.

For decades now, antibiotics have been regularly fed to farming livestock to help them fight off diseases typically found when keeping animals in confined spaces for long periods of time, particularly in China, where this practice has led to widespread criticism of the practice ushering us into a post-antibiotic age.

Now, a new study published in Proceedings of the Royal Society B looking into the ramifications of this practice has analysed tons of cow dung and, it’s safe to say, the results are not pretty.

During lab tests, the team determined that dung laced with antibiotics would create twice as much methane than typical cow dung, which is already one of the greatest contributors to damage to the environment, aside from our industrial world.

The team analysed 10 cows’ dung in total, giving half of them a three-day course of a common broad-spectrum antibiotic called tetracycline, with the other five given none.

Also makes the cows’ belches more harmful

They then piled the two groups’ dung into two buckets to measure and compare flows of gases like carbon dioxide, methane and nitrous oxide and found the antibiotic dung had increased methane emissions of 1.8-fold.

“Antibiotics are extensively used in agriculture to promote growth and to treat or prevent livestock disease, yet they may have major consequences for human and environmental health,” said the study’s authors.

“We provide the first demonstration that antibiotics can increase dung emissions of methane.”

The likely answer as to why this is happening, the team said, is that the antibiotics are changing the microbial activity in the cow’s gut, with suggestions it could also contribute to increased methane emissions from cow belches, which is known to contribute more of the noxious gas than dung.

Now, the team said, it plans to go and conduct further studies to better quantify the contribution of agricultural antibiotic use to climate change.

Sorry-looking cow image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic