With scientists taking a hard look at the numerous effects of global warming and the drivers behind it, a new study reveals a new potential threat to Earth's climate: the dung of cattle that consume antibiotics.
In the study, the team conducted laboratory experiments that discovered that the dung pats from animals that consume a common antibiotic release more than double the amount of methane, a potent greenhouse gas, compared to cows that were not treated with antibiotics.
Treating animals with antibiotics has already led to drug resistance in humans, and the new data highlights yet another danger of the practice.
"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," the authors wrote. "We provide the first demonstration that antibiotics can increase dung emissions of methane."
The team collected dung from 10 cows - five that were treated with a three-day course of the common antibiotic tetracycline, and five that were not treated with any antibiotics. After breaking down the dung into smaller pats, the team placed the pieces in open buckets in the field along with empty buckets and measured and compared the release of gases such as methane, nitrous oxide and carbon dioxide.
The results revealed that antibiotic treatment "consistently increased methane emissions" by nearly 1.8-fold.
Agriculture is responsible for approximately one-fifth of global greenhouse gas emissions, and methane in particular is 20 more efficient at trapping solar heat - which contributes to climate warming - in comparison to other greenhouse gases.
Why exactly do antibiotics increase greenhouse gas emissions? The University of Colorado at Boulder team believes that they likely alter microbial activity within the gut of the livestock, which could also increase methane emissions through belching.
Antibiotic treatment in farm animals is already under scrutiny in many countries - including the U.S. - due to its contribution to drug resistance in humans, which increases the dangers of diseases that would otherwise be easily treatable.
Further research will need to be conducted to determine the exact relationship between antibiotic treatment in livestock and global warming.
The findings were published in the May 25 issue of the Proceedings of the Royal Society B: Biological Sciences.
