The researchers from the Johns Hopkins Bloomberg School of Public Health found that the price of the feed offset the extra weight gained by the chickens. Overall, farmers lost about one penny per chicken, but the added labour makes the cost much heavier. Furthermore the results didn't take into account potential changes in veterinary costs from switching to antibiotic-free feed, nor medical and public health costs incurred from treating antibiotic-resistant illnesses.

The study analyzed the marginal profits associated with drug additives in comparison to the costs of utilizing these drugs. The data used in the analysis were compiled by the Perdue Corp., a leading broiler-poultry producer. When the reports findings became evident Perdue discontinued use of antibiotics in its poultry. It is thought that many may now follow suit.

"Although Perdue has discontinued the use of growth-promoting antibiotics, our study remains relevant both in the United States and internationally," said Graham, lead author of the study. "Roughly two-thirds of the 8.7 billion broiler chickens raised in this country are fed antibiotics throughout their life. Internationally, poultry production is growing rapidly, mostly in developing countries where there are limited controls on antibiotic use for animals. Further, the results of our study help dispel the myth that growth-promoting antibiotics are vital to raising poultry."

According to Silbergeld, co-author of the study, the public health community has long since had concerns about the potential misuse of antibiotics in food animal production. "This practice has been associated with the dangerous increases in the number of antibiotic-resistant infections in people worldwide," she said. "Our study considered the economic costs and benefits of antibiotic feed additives, and the results suggest that the industry should rethink its practices from a business perspective."

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