In the 1920s, a bizarre and deadly mystery was plaguing cattle in the United States and Canada. Cows were bleeding to death from the smallest cuts—or sometimes, for no reason at all! It was as if a curse had fallen upon the herds.

The Truth Turned Out to be Stranger than Fiction 

Researchers discovered that the cows were munching on moldy sweet clover hay. This hay contained a sneaky substance that stopped their blood from clotting. Fast forward to 1940, and chemist Karl Paul Link at the University of Wisconsin managed to isolate the culprit, a compound called dicoumarol.

But the Story Doesn’t End There 

Dicoumarol eventually led to the development of warfarin, named after the Wisconsin Alumni Research Foundation (WARF). Initially, warfarin was used as a rat poison—it was powerful enough to make rodents bleed out, just like those unlucky cows.

Then Came an Unexpected Twist

in 1951, a Navy recruit tried to take his own life by ingesting warfarin. Amazingly, he survived after being treated with vitamin K. This incident got scientists thinking: what if warfarin could be tamed? And they were right—when given in carefully controlled doses, warfarin became a life-saving blood thinner for humans, revolutionizing the way we prevent blood clots.