USDA scientists are working on a method to reduce odor and pathogens in manure by using thymol, an herb derivative.

Thymol is the active component in thyme oil, which can be extracted from a variety of plants, such as thyme and oregano. Because of its pleasant odor and natural antiseptic properties, thymol appears in a variety of products, including mouthwash and throat lozenges. However, USDA Agricultural Research Service microbiologists Elaine Berry, Vince Varel and Jim Wells discovered that its qualities also can benefit livestock operations.

When applied to feedlot soil in slow-release granules, thymol reduced concentrations of odor-causing volatile fatty acids (VFAs) and pathogens like coliform bacteria and Escherichia coli. Berry, Varel and Wells work in the ARS Nutrition Research Unit, part of the agency’s Roman L. Hruska U.S. Meat Animal Research Centerin Clay Center, Neb.

The researchers observed even more prolonged effects in swine facilities, which might be due to the pits some swine operators use to collect and store manure. The enclosed systems could retain more thymol than the cattle feedlots, increasing its effectiveness.

The scientists also tested less-expensive compounds in the lab, including terpineol, linalool, plinol and geraniol. Most promoted reduction of VFAs and pathogens like E. coli and Salmonella. Linalool was nearly as effective as thymol in the lab, but when subjected to field studies in the feedlot, thymol outperformed it. This may have been due to dry weather conditions during the test period, the researchers speculate. They plan to conduct more tests in the spring, when feedlot conditions will more closely resemble the slurries in which they initially tested the compounds.

USDA Agricultural Research Service