Factbox: U.S. antibiotic phase-out may have minimal impact on livestock

CHICAGO (Reuters) - The U.S. Food and Drug Administration's planned phase-out over the next three years of some antibiotics used in animal production could have a minimal immediate impact on cattle, pork and chicken production, said economists and traders. FDA on Wednesday outlined a proposal that would help reduce the use of some antibiotics in animal production to counter bacterial resistance to those drugs when they are prescribed for humans. In its statement on Wednesday, the agency did not specify which antibiotics would be targeted. Some of the country's biggest pharmaceutical companies such as Eli Lilly & Co and Zoetis would be affected. * It appears FDA aims to halt or curtail the use of antibiotics for weight gain, Chicago-based Daniels Trading commodities broker Craig Turner told Reuters. * FDA's plan will mean cattle weights could come down over the long term resulting in less supply, which may be bullish for cattle prices in the future, he said. * Since the early 1950s, antibiotics and antimicrobials, which inhibit the spread of micro-organisms or kill them, have been used in feed or drinking water of livestock for food production, which ultimately help promote animal health which could improve weight gain, livestock economists said. * They said some of those antibiotics are also used to treat infections in humans, raising concerns about increased bacteria resistance against a drug. * On April 11, 2012, FDA finalized a guidance document "The Judicious Use of Medically Important Antimicrobial Drugs in Food-Producing Animals", according to a copy obtained by Reuters. It helped act as a blueprint for the document announced on Wednesday. * To minimize cross-over resistance, a majority of antibiotics that are used by the livestock industry are not currently used in human medicine, said Purdue University assistant professor of meat science Jolena Waddell told Reuters. * "The FDA and most agencies also consider ionophores to be antibiotics because they select for good, more productive bacteria in the rumen of cattle, which increases their growth and efficiency. These are widely used and do not coincide with any drugs on the human side, so this should not be affected," she said. * Antibiotics will still be used in prevention and treatment of disease outbreaks, especially in nursery pigs, Waddell said. * "It is like taking your kid to daycare for the first time—they are going to share germs and get sick," Waddell said. Medicated feeds prevent huge production losses and prevent animal suffering at these critical points, but they are expensive and are used judiciously, she added. (Reporting by Theopolis Waters in Chicago; Editing by Bob Burgdorfer)