The horse was found injured in a field near Tibberton, and police want anyone with information to come forward.
A statement by West Mercia Police said: "The mutilation of a dressage horse in a field at Tibberton was reported on Friday, March 15.
"A vet said that the horse could not have injured itself and the animal had to be put down.
Anyone with information is asked to call 101 and refer to incident number 0557s of March 15.
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org