Police in West Cornwall, England, say those responsible for releasing stock from pastures and sabotaging water troughs will face criminal damage charges if caught.
There have been a spate of such incidents across the grazed moorland, which have seen horses and cattle escape on to roads, Devon and Cornwall Police said.
The incidents have been ongoing since 2008, but they are getting more common.
One farm has been hit more than 15 times since September.
Sergeant Cara Trott said: “Police are investigating these incidents and anyone caught will be prosecuted for criminal damage.
“Whatever the motive, these incidents are criminal and are also extremely dangerous. Cattle and ponies getting onto the winding roads where people are not expecting them could result in someone getting killed.
“I would urge anyone carrying out these offences to stop before someone is seriously injured.
“We will do everything we can to find out who is responsible so that these farming families can live without the fear of continually being victimised.”