Antibiotic Residues in Distillers' Grain?
Distillers' grains continue to be the subject of controversy. Maybe, as a beef cattle nutritionist once said, it's because distillers' grains are almost too good to be true. Indeed, its nutritive value has turned a once burdensome "byproduct" that ethanol processors sometimes gave away into a marketable "coproduct" used increasingly in a variety of livestock diets. But there have been questions raised, quelled and resurrected about how feeding distillers' grains might affect animal health and both the eating quality and safety of beef. For the most part, distillers' grains have been a good, safe feed ingredient for cattle producers having access to the product and the ability to incorporate its use, particularly in finishing rations.
But now distillers' grains are under scrutiny for containing antibiotic residues. In 2008, the Food and Drug Administration (FDA) requested samples of the coproduct from 60 U.S. ethanol processors. Reportedly, analyses revealed residues from antibiotics including virginiamycin, erythromycin and tylosin. This has raised concern that trace residues in distillers' grains fed to cattle might contribute to the development of strains of antibiotic-resistant bacteria, and that similar antibiotics used to treat bacterial infections in humans might eventually become less effective.
Antibiotics in ethanol production
Along with raising corn and running a commercial Angus cow herd, Duane Kristensen is manager of Chief Ethanol Fuels Inc., in Hastings, Neb., and he currently presides over the Association of Nebraska Ethanol Producers. Kristensen says one of the challenges of commercial ethanol production is a pesky bacterium that can interfere with yeast action during the process of fermenting corn. Consequently, many ethanol producers use antimicrobial products to combat bacteria, and some of those products contain one or more antibiotics.
Kristensen believes continuous-flow plants, like Chief Ethanol Fuels, may have fewer problems with bacterial contamination than do batch facilities. He says Chief Ethanol has used antimicrobials containing antibiotics but it is not a routine practice.
"Not all ethanol distillers use antibiotics routinely, although that seems to be the generalized perception," Kristensen states. "We have used them here, under extreme circumstances, to clear up a bacterial problem. And we have used other kinds of antimicrobials, so bacteria can't adapt to one kind and become resistant."
Some other products that contain no antibiotics rely on chlorine dioxide and hydrogen peroxide — a technology used for water purification. Another type of product utilizes the antimicrobial properties of an enzyme extracted from hops, the same hops used in the brewing of beer.
But the use of antibiotics and the detection of residues in distillers' grains doesn't mean that ethanol processors are breaking any rules or regulations. Actually, not many rules apply. The FDA has rendered an opinion on the use of one antibiotic for use in ethanol production. And that was a letter of "no objection" regarding the use of a product called Lactrol®, which contains virginiamycin.
Tom Slunecka, a representative for Lactrol manufacturer Phibro Animal Health, says the product was submitted to FDA for review. He says antimicrobial products are important to ethanol production, allowing the industry to gain an extra 1.5 billion gallons of ethanol from the corn feedstock currently used. Put another way, the judicious use of antimicrobials eliminates the need for an additional 3.2 million acres to produce an extra 500 million bushels of corn.
"Ethanol producers also use other products, which contain different antibiotics, but that doesn't mean they are doing anything wrong. There are no 'unapproved' antibiotics for ethanol production," Slunecka states. "But the manufacturers of other products probably will have to go through the same process our company did, and seek an FDA review."
Perception vs. science
According to Laura Alvey, spokesperson for FDA's Center for Veterinary Medicine (CVM) the letter of "no objection" was issued to allow the use of virginiamycin when the antibiotic is added during the fermentation phase of ethanol production, at the rate of two to six parts per million (ppm), and when resulting coproduct (distillers' grains) has a residue level of 0.2 to 0.5 ppm, with the maximum value dependent upon the inclusion rate of coproduct in a livestock ration.
However, Alvey says the letter was based on a safety assessment that "assumed a 20% maximum inclusion rate of distillers' dried grains with solubles in an animal's diet," on a dry-matter (DM) basis. Increasingly, feedyards are using higher inclusion rates. A rate of 40% is common, and some are higher. Because of its limited data regarding the extent and levels of antibiotics in ethanol coproducts used for animal feed ingredients, and because of the marked increase in ration inclusion rates, FDA/CVM decided to conduct a survey of distillers' grains produced by U.S. facilities and foreign facilities marketing their products in the U.S.
"Although our method was able to detect virginiamycin, erythromycin and tylosin at residue levels, we have not conducted a health risk assessment and cannot comment on the potential for any adverse health risks to humans and food animals," says Alvey, adding that no estimated time frame for publishing survey results has been set.
FDA/CVM did launch an outreach program, urging antimicrobial product suppliers to submit a Food Additive Petition from which a regulation could be published with regard to the specific products and the antibiotics they contain.
Steve Ensley, a toxicologist at Iowa State University College of Veterinary Medicine, says the outcome of the antibiotic residue issue depends on the stance FDA eventually takes. He doubts the residue levels create any animal health or food safety consequences. Rather, the issue is likely to be whether residues are perceived to promote antibiotic-resistant bacteria and pose a risk to human health. And perception often trumps science.
"We can only speculate where the FDA may go with this, and whether there will be any future regulatory action," Ensley states. "My advice to cattle producers is to stay tuned for further developments."
According to Laura Alvey, FDA recommends cattle producers talk to their suppliers, know how they are producing their distillers' grains and determine which suppliers are right for them.