The results of a study on antibiotic residues in distillers grains has been published in the Journal of Animal Science. It concluded that 12.6 percent of the distillers grains samples contained low antibiotic concentrations that were biologically inactive and only one sample inhibited growth of E. Coli. “The inhibition in only one distillers grains (DG) sample by sentinel bacteria suggests that antibiotic residues in DG were inactivated during the production process or are present in sublethal concentrations,” the manuscript’s abstract said.

The study was completed in 2012 and was featured in an August 2012 Ethanol Producer Magazine story called “Testing for Traces.”  It was conducted by six researchers from the University of Minnesota Department of Animal Sciences, the U of M Extension Service and the Department of Food Science and Nutrition and one person from SGS North America Inc. Funding for the study was provided by the Minnesota Corn Research and Promotion Council.

In all, 159 samples were collected, including 80 samples of dry distillers grains and 79 samples of wet distillers grains. The majority of the antibiotic residues were found in the dry distillers grains, with 21.3 percent of the samples containing antibiotic residues. On a dry matter basis, 3.8 percent of the wet distillers grains samples contained antibiotic residues.

Researchers pointed out that the samples with antibiotic residues contained low concentrations that were “well below dietary concentrations of current FDA-approved antibiotic for finishing livestock and poultry feeds.” The lack of bacterial inhibition in the samples was due to antibiotic inactivation, researchers said. Conditions of ethanol production, including low pH values of distillers grains and high temperatures reached during fermentation, distillation and distillers grains drying, may have contributed to the inactivation.