U.S. Department of Agriculture investigates citrus peels as antimicrobial substitute

Washington — More than a decade of research by the United States Department of Agriculture's (USDA) Agricultural Research Service (ARS) indicates that citrus peels, specifically a compound called d-limonen, may be a viable substitute for antimicrobials in livestock.

The studies, dating back to 1999, have shown that citrus oils can kill Staphylococcus aureus, Pseudomonas, Salmonella and Escherichia coli. In fact, researchers have demonstrated that a small amount of orange peel and pulp added to a mixture of laboratory ruminal fluid fermentations reduced E. coli O157:H7 and S. Typhimurium populations, and the same products fed to weaned swine reduced intestinal populations of diarrhea-causing E. coli.

While citrus byproducts may be economical to obtain, shipping them long distances is not, USDA says. So the research team developed processed orange peel pellets. When fed to a sheep for eight days, USDA says the research team noted a 10-fold reduction in Salmonella and E. coli O157:H7 in the animal's intestinal contents.

Additional field trials are now being planned to test citrus byproducts at ARS, the University of Arkansas and the University of Florida, says USDA.

The research team includes ARS microbiologist Todd R. Callaway; animal scientist Tom S. Edrington with the Food and Feed Safety Research Unit in College Station, Texas; ARS animal scientist and research leader Jeffrey Carroll with the Livestock Issues Research Unit in Lubbock, Texas; and John Arthington, director and professor at the Range Cattle Research and Education Center at the University of Florida in Ona, Fla.