The European Union banned the use of antibiotics to boost animals' growth in 2006. At first, the ban had little effect on the amount of drugs given to pigs. Carsten Rehder/Corbis hide caption

itoggle caption Carsten Rehder/Corbis

Piglets in a pen on a hog farm in Frankenstein, Mo. Jeff Roberson/AP hide caption

itoggle caption Jeff Roberson/AP

Craig Rowles tends to his pigs in a barn near Carroll, Iowa. Dan Charles/NPR hide caption

itoggle caption Dan Charles/NPR