With recent increased attention by the Food and Drug Administration (FDA) over the use of antibiotics in livestock production, industry experts are turning their attention to potential non-farm sources of antibiotic residues. Could distillers’ dried grains with solubles (DDGS), a co-product of ethanol production widely used in livestock feed, contain antibiotic residues even before reaching the farm?
Ethanol producers are currently operating 209 U.S. plants which produced about 39 million metric tons of co-products used in poultry and animal feed in 2011, according to the Renewable Fuels Association. For every bushel of corn used in the manufacturing process, 2.8 gallons of ethanol are produced plus 17 pounds of animal feed ingredients.
Bacterial contamination during the fermentation step of ethanol production can be a challenge and can reduce the yield by 1 percent to 5 percent, according to research estimates. “Bacteria compete with yeast for nutrients and cause incomplete fermentation resulting in reduced ethanol yields.” according to leading DDGS researcher, Dr. Jerry Shurson, University of Minnesota professor of swine nutrition.
Antibiotics, such as virginiamycin and penicillin, are used to manage the problem.
To examine the potential for antibiotic residues resulting from including DDGS in swine diets, Shurson and his coworkers tested 159 DDGS samples collected by independent nutritional consultants. While small amounts of antibiotic are used in ethanol production to maximize output, Shurson says the production process renders the antibiotic biologically inactive. “Based on research information published in the scientific literature, the antibiotics being used in ethanol production appear to be inactivated due to the high temperatures and/or low pH that they are exposed to during ethanol and DDGS production,” Shurson says.
Shurson’s research results show that very small amounts of some antibiotic residues are detectable in distillers' grains, but they generally had no biological activity when extracts were tested with sentinel strains of E. coli and Listeria monocytogenes. “The amounts of antibiotics used in ethanol production are well below the amounts that are approved by FDA for use in swine feeds,” he adds.
The amounts of residues remaining in DDGS are miniscule compared to the amount initially added, according to Shurson “In addition, the miniscule amounts of these antibiotics do not have biological activity. Only 1 in 159 samples extracted showed biological activity for E coli but none for Listeria monocytogenes.”