Using data from poultry giant Perdue, the researcher found that antibiotics slightly accelerated chicken growth, but that the benefit was offset by the cost of purchasing antibiotics, with the total cost rising by about one penny per chicken. The Johns Hopkins study is in line with a 2002 study by researchers at Kansas State University showing that the use of growth-promoting antibiotics provided no economic benefits during the "finishing" stage of pig production, when weaned pigs are grown to market-weight. 

US in line with Europe
Europe has already banned the use of growth promoting antibiotics. In the US, around 70% of all antibiotics used (nearly 25 million pounds annually) are used as feed additives for chicken, pigs, and beef cattle according to estimated by the Union of Concerned Scientists. At the same time, Perdue and three other large poultry producers: Tyson, Gold Kist, and Foster Farms say they no longer use antibiotics to promote growth, although there is no way to verify these claims.
In addition, companies such as McDonald's and Compass Group, one of the largest contract food service companies in North America, have adopted policies that prohibit the purchase of certain meats if the animals were given antibiotics important in human medicine to accelerate their growth.

The study, "Growth Promoting Antibiotics in Food Animal Production: An Economic Analysis," appears in the January-February issue of Public Health Reports. It was written by Jay P. Graham, MBA, MPH, John J. Boland, PhD, and Ellen Silbergeld, PhD, at the Johns Hopkins Bloomberg School of Health.