An Agricultural Research Service (ARS) pilot study found that composting beef cattle manure can reduce antibiotic concentrations in the manure by more than 99%. Osman Arikan, a visiting scientist from Istanbul Technical University, and ARS microbiologists Patricia Millner and Walter Mulbry, Beltsville, MD, evaluated varying levels of manure management, including plain manure piles and manure piles with straw added. They found adding straw to manure piles tends to result in higher temperatures that speed up the process of degrading both antibiotics and pathogens.

Previous scientific studies have shown between 20 to 75% of antibiotics administered to animals can be excreted via urine and feces. The amount of antibiotic excreted varies depending on the antibiotic and type of animal. Arikan, Millner and Mulbry researched the effectiveness of a series of minimal–management options for on-farm composting to reduce concentrations of oxytetracycline and chlorotetracycline.

When manure-only piles were incubated at ambient temperatures over a 28-day period, concentrations of oxytetracycline and chlorotetracycline decreased by 75% and 90% respectively. By comparison, manure piles that had been amended with straw tended to experience a 91% decrease in oxytetracycline and 99% reduction in chlorotetracycline concentrations over the 28-day incubation period. The researchers say although manure piles amended with straw attained higher temperatures and more rapid decreases in antibiotic concentrations, there is currently no compelling justification for producers to expend additional resources needed to achieve the more rapid rates of antibiotic removal. They also stress it is important to manage manure piles carefully and consistently to make sure all parts of the pile are treated in order to reduce pathogens. Learn more about the project online.