The credit for the discovery that antibiotics in stable form added to feedstuffs (in amounts so small that they resemble vitamins) have growth-promoting properties, goes to Lederle Laboratories, a subsidiary of the American Cyanamid Company. This was in 1948 and was revealed during studies with residues following the manufacture of aureomycin. It was found that these were a rich source of vitamin B12 which had been discovered to have growth-promoting properties when added to all-vegetable diets. But the aureomycin residues contained a further stimulus to growth which was later found to be related to the antibiotic itself.