Farmers in Liechtenstein can no longer feed cannabis to their herds under new rules in the small Alpine state.
The hemp tree is part of the cannabis species
Traces of the drug found in hashish have been filtering through to the milk of dairy cows fed with the hemp plant.
The levels breach the maximum limit set by the new rules - which say animal feed must be free of any element that could have an ill effect on humans.
The rules to be introduced in March are to bring Liechtenstein in line with standards in neighbouring Switzerland.
Hemp will also be banned from the diets of meat herds, although reports say there is no clear evidence that THC - the active substance found in hashish - can filter through into meat.
The hemp tree is part of the cannabis species, which includes marijuana plants.