IDIOT animal rights activists KILLED four cows and left 40 others critically ill after releasing them into a feeding pen where the beasts "ate themselves to death".

Suspects are believed to have trespassed onto an organic farm in Germany on Saturday night and released dozens of dairy cows and calves.

The cows then headed straight to the feeding pen where they ate up to 10kg of concentrated feed with catastrophic results.

They are normally fed a maximum of 2kg a day.

Anja Schiemann, the farm's managing director, told the Berliner Zeitung: "Too much concentrate feed causes the digestive system in the rumen to be severely disturbed.

"The damage to the liver is just too much."

The Liebenwalder Agrar farm is set to suffer financially from the incident, and it is not yet known if the sick cows will make a full recovery.

Police are investigating, and the farm has offered a £890 reward for information.