A new study has suggested that the recently announced plan by US fastfood giant McDonald's to encourage meat producers to curb the use of antibiotics could cause a US$700m economic backlash in the pork industry.

The study, carried out at Iowa State University, estimates that cost increases and production declines from a ban on antibiotics in meat production could force some producers out of business, reported the Associated Press.

McDonald's announced in June that it would direct some meat suppliers to stop using antibiotic growth promoters and encourage others to cut back, in response to warnings that widespread use of antibiotics on US farms could decrease their effectiveness in human medicine.

The policy will prohibit McDonald's direct suppliers, which mainly supply chicken, from using 24 growth promoters that are closely related to antibiotics used in human medicine. It will be effective worldwide by the end of 2004 and will require suppliers to keep records and agree to regular audits

"I think they [McDonald's] feel that consumers are concerned or will be concerned," Helen Jensen, an ISU professor of economics and co-author of the study, was quoted by AP as saying. "They have sufficient force in the market to force suppliers to change."