Herbs are often used to offset odors, but even those involved with animal manure? USDA scientists are working on a method to reduce odor and pathogens in livestock 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 aroma 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 have 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 and pathogens like Coliform bacteria and E. 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 when thymol was used in swine facilities. In buildings with deep- or shallow-pit systems, the enclosed systems could retain thymol, thereby 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 laboratory, but when subjected to feedlot studies, thymol outperformed it. The researchers speculate that dry weather conditions during the test period may have influenced those results. They plan to conduct more tests this spring, when conditions will more closely resemble the slurries in which they initially tested the compounds.