Managing cattle manure can prevent antibiotic-resistant bacteria from contaminating crops, new study finds

Unmanaged cow manure can cause antibiotic-resistant bacteria
to proliferate. (Adobe Stock photo)

Manure and antibiotic management on cattle ranches can help prevent the growth of more antibiotic-resistant bacteria, a new study finds.

Researchers have uncovered substantial evidence that unmanaged livestock manure poses a global health risk by transmitting antibiotic-resistant genes (ARGs) when spread in fields or used to water crops.

When antibiotics are used to treat livestock, resistant bacteria and their resistance genes "can build up in cattle guts, which is then excreted into manure," reports Pragathi Ravi for Offrange. Antibiotic-resistant bacteria and their genes "reduce the effectiveness of critical medicines on humans." 

Giving farm animals antibiotics only when they are ill -- not as a way to promote growth -- is one way to prevent antibiotic-resistant bacteria and genes from multiplying, according to the World Health Organization. 

One problem with antibiotic-resistant bacteria or genes is that once they have sickened a human, there is no viable treatment. Ravi adds, "In 2021, a study published in The Lancet estimated that 4.71 million deaths were associated with antimicrobial resistance between 1990 and 2021."

Humans can become ill from contact with untreated manure or from ingesting food fertilized or watered with unprocessed manure that contains bacteria. Ravi explains, "Salmonella can grow inside a tomato, which means washing it externally is not going to help when the tomato is consumed raw."

Study researcher and professor Xun Qian told Ravi: "Livestock manure carries antibiotic resistance genes that can defeat every major class of antibiotics used in human medicine — including those considered ‘last resort.'" 

Implementing programs that support proper manure composting before it is applied to farmland can help prevent ARGs from spreading.