Police have launched an investigation after four horses were attacked in their fields in the Bonnybridge area.
One of the animals was so badly injured it had to be destroyed by its owners.
Another three horses, stabled at different locations, also received cuts to their bodies between 30 May and 6 June, Central Scotland Police said.
The force has warned farmers and animal owners in the area to be vigilant. Patrols in the area have also been increased.
Insp Paul Fleming of Denny police station, said: “To get that close to a horse, a great deal of time has to be spent befriending it.
“The person who has done this is obviously comfortable around horses.
“I appeal for anyone with information or who sees anything suspicious to contact us.”
Source: BBC News