Livestock producers and their nutritionists have been wondering whether antibiotic residues from the ethanol fermentation process might linger in the distiller's co-products used in livestock diets.

Lora Berg 1, Editor

March 14, 2012

2 Min Read
Co-Product Antibiotic Levels Nearly Nil


A recent University of Minne­sota study indicates distillers’ grains with soluble (DGS) do not contain significant antibiotic residues to be of concern to livestock producers.

Antibiotics are added during ethanol fermentation to control bacterial contamination. Bacteria compete with yeast during the ethanol fermentation process, which can lead to a reduction in ethanol yields and reduced-quality DGS. Virginiamycin and penicillin are designated by the U.S. Food and Drug Administration (FDA) as generally recognized as safe (GRAS) for use in ethanol and DGS production, though they are not the only antibiotics being used.

Livestock producers and their nutritionists have been wondering whether antibiotic residues might linger in the distiller’s co-products used in livestock diets and if they have any biological activity.

Seeking answers, Devan Paulus, a graduate student working with Jerry Shurson, swine nutritionist at the University of Minnesota, collected 20 distiller’s (wet) grains with solubles (DGS) samples and 20 distiller’s dried grains with solubles (DDGS) samples from various ethanol plants throughout the United States. The samples, collected quarterly for a year, were analyzed for virginiamycin, erythromycin, penicillin, tetracycline and tylosin residues. Further testing on E. coli and Listeria monocytogenes sentinel bacteria revealed whether the residues were active.

While all of the 117 samples tested to date contained antibiotic residues, only one sample was found to have an antibiotic residue active enough to inhibit E. coli growth. The residue concentrations in the distillers’ grains are much lower than minimum-approved Food & Drug Administration (FDA) feed levels for finishing swine. “Extremely low concentrations of penicillin (less than 0.2 ppm), erythromycin (less than 1 ppm), tetracycline (less than 0.008 ppm) and tylosin (less than 0.02 ppm) residues were detected in wet and dried distillers’ co-products,” Shurson explains. “Only two of the 117 samples contained low, but detectable, concentrations (0.5 and 0.6 ppm) of virginiamycin residues, but this level is well below the 1 ppm FDA GRAS approval level,” Shurson explains.

“It appears that there is minimal, if any, concern about residues having inhibitory properties when tested with the sentinel bacteria; thus, it is likely that the majority of antibiotic residues in distillers’ grains are inactivated during the ethanol fermentation process and subsequent derivation of distillers’ grains,” he adds. 


Lora Berg is a freelance writer from Lakeville, MN.

About the Author(s)

Lora Berg 1

Editor, National Hog Farmer

Lora is the editor of National Hog Farmer. She joined the National Hog Farmer editorial team in 1993, served as associate editor, managing editor, contributing editor, and digital editor before being named to the editor position in 2013. She has written and produced electronic newsletters for Farm Industry News, Hay & Forage Grower and BEEF magazines. She was also the founding editor of the Nutrient Management e-newsletter.

Lora grew up on a purebred Berkshire operation in southeastern South Dakota and promoted pork both as the state’s Pork Industry Queen and as an intern with the South Dakota Pork Producers Council. Lora earned her bachelor’s and master’s degrees from South Dakota State University in agricultural journalism and mass communications. She has served as communications specialist for the National Live Stock and Meat Board and as director of communications for the University of Minnesota College of Agricultural, Food and Environmental Sciences. During her career, Lora earned the Story of the Year award from the American Agricultural Editors’ Association and bronze award at the national level in the American Society of Business Publication Editors’ competition. She is passionate about providing information to support National Hog Farmer's pork producer readers through 29 electronic newsletter issues per month, the monthly magazine and website.

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