Microbes in Manure Can Minimize Potential Pharmaceutical Pollution

Bacteria are usually viewed as “the enemy” and targeted with potent antibiotics to curb their ability to cause infection. But according to Agricultural Research Service (ARS) scientists, microbes--including several types of bacteria--can be a farmer’s ally when it comes to reducing the risk that antibiotic-containing manure may pose to the environment.

Livestock and poultry producers rely on antibiotics to treat a host of diseases and infections. In fact, more than 21 million pounds of antibiotics were administered to U.S. farm animals and pets in 2004. Such treatments help promote animals’ health and well-being, in addition to ensuring a safe food supply for consumers.

The trouble is, when animals excrete in their waste antibiotics and other pharmaceuticals that their bodies don’t use, the compounds may linger in the environment. This so-called pharmaceutical pollution can encourage bacteria to mutate and form strains that are resistant to current antibiotics.

Scott Yates, a soil scientist with ARS’ George E. Brown, Jr. Salinity Laboratory in Riverside, Calif., wanted to find out what happens to antibiotic-laced manure once it’s mixed with soil, as typically happens when livestock manure is spread onto farm fields as a fertilizer.

Yates and colleague Qiquan Wang studied one commonly administered veterinary antibiotic, sulfadimethoxine, which is used to combat a number of diseases in livestock and pets.

They developed a mathematical model which revealed that thriving manure microbes play an important role in determining how quickly sulfadimethoxine degrades. Some microbes in manure can digest and inactivate the excreted antibiotic.

According to Yates and Wang, farmers should try to create a hospitable environment for these tiny helpers. They should store waste from treated animals in a warm, moist place for as long as possible before spreading it onto fields. This gives the beneficial soil microbes an opportunity to act on an antibiotic, before it has the chance to leach into soils and waterways.

ARS is the U.S. Department of Agriculture’s chief scientific research agency.