A tall, rubbery weed with golden flowers Dalmatian toadflax is encroaching on grasslands in 32 U.S. states. pverdonk/Flickr hide caption

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Beef cattle stand in a barn on the Larson Farms feedlot in Maple Park, Ill. Daniel Acker/Landov hide caption

itoggle caption Daniel Acker/Landov

A pen at a feedlot in central Kansas that houses 30,000 cattle. Feedlots are where cattle are "finished" before slaughter, often with the use of growth-promoting drugs like zilpaterol. Peggy Lowe/Harvest Public Media hide caption

itoggle caption Peggy Lowe/Harvest Public Media

Whenever a steer or cow leaves a farm in Michigan or goes to a slaughterhouse, it passes by a tag reader, and its ID number goes to a central computer that keeps track of every animal's location. Dan Charles/NPR hide caption

itoggle caption Dan Charles/NPR