Pigs at a farm in Beijing peer out at visitors. Half of all the pigs in the world live in China. Ng Han Guan/AP hide caption toggle caption Ng Han Guan/AP The Salt Pig Manure Reveals More Reason To Worry About Antibiotics February 11, 2013 Manure from pig farms doesn't just contain residues of antibiotics used in livestock. It also carries high concentrations of antibiotic-resistant bacteria, a new study of Chinese pig farms finds. And researchers say "it's a global problem."