A new study has linked increases in greenhouse-gas emissions with livestock given antibiotics. The paper, published in Proceedings of the Royal Society B, purports that when cattle are administered tetracycline, their dung produces more methane than that of cattle not given the antibiotic.
“This is the first report that we’re aware of that shows antibiotics having this increased effect on methane release,” Tobin Hammer, the study’s co-author from the University of Colorado, told the ABC.
“We think it’s because of microbial competition going on inside the cattle’s intestines where the balance is altered by antibiotics.”
Hammer explained that, should their hypothesis be right, it could have dire consequences for the environment. Particularly if the antibiotic also modifies direct gaseous emissions, which account for the majority of cattle methane production.
“If this effect also occurs for belching, I think that would be maybe cause for concern,” he said.
The methane produced by cattle is formed by the activity of archaea gut microbes; ingestion of tetracycline increases their prevalence.
Hammer and his team measured the amount of methane, carbon dioxide and nitrous oxide produced in the dung of cattle that had been fed tetracycline and compared it with regular cattle dung.
The scientists found a vast increase in archaea, and therefore methane, in the former. They also found a large difference in the microbiota.
“The relative abundance of archaea that produce methane increased with antibiotic treatment, and that presumably is why we saw a strong increase in methane emissions,” said Hammer.