Antibiotic-fed cows, burping and farting may lead to climate change; Tetracycline releases potent greenhouse gas methane

A new study, published in Proceedings of the Royal Society B, has revealed that feeding cows with antibiotics may increase greenhouse gas emissions from cow dung, burps and farts. Cows feeding on antibiotic tetracycline produce more methane, a potent greenhouse gas, than any other animals not fed with the antibiotic.

Study co-author Tobin Hammer, from the University of Colorado, explained that if the study’s hypothesis is correct, then the antibiotic tetracycline will have the same effect from the animals as well on direct gaseous emissions. The animals will produce methane that will in turn contribute to climate change.

The study is first of its kind that shows antibiotics have an increased effect on methane release. Hammer believes that antibiotic tetracycline alters the microbial competition inside a cow’s intestine and also hampers the balance. He added that if the same effect occurs for belching, that would be a cause of concern.

Livestock is a known source of methane, which is a more potent greenhouse gas than carbon dioxide. Hammer and his colleagues in Finland analysed dung of cows fed with antibiotic tetracycline and compared to dung of cows not fed with any antibiotic. They measured the amount of carbon dioxide, nitrous oxide and methane emitted by the cow dung.

Activity of gut microbes in cow intestines produces methane. The gut microbes are known as archaea. They thrive in air-free conditions. The scientists believe that tetracycline alters the balance of the gut microbes towards the methane-producing types. The study showed drastic changes in the microbiota of the dung and an increase in methane emissions in dung of cows fed with the antibiotic. Tetracycline may also increase methane content of cow farts and burps.

As dung beetles break down cow pats, recycle nutrients and reduce methane emission by reducing anaerobic archaea and oxygenating the dung, the scientists also studied the impact of the antibiotic on dung beetles. Interestingly, the dung beetles also had a changed microbiota. Although the beetles reduce methane emissions, it was not enough to offset the increase in emissions as a result of feeding antibiotics.