The anticoagulant was discovered when farmers in poverty-stricken 1920s America were forced to feed cattle damp or mouldy hay and noticed seemingly healthy animals dying from internal bleeding.
It turned out that a mould in the hay contained an anticoagulant called dicoumarol.
In 1940, scientists at the University of Wisconsin-Madison isolated the compound, paving the way for mass manufacture of warfarin.
Although it’s widely used in humans, it also gained notoriety as a deadly rat poison. - Daily Mail