Police investigating a series of attacks on animals think they could be linked to pagan rituals.
The horses all needed treatment by a vet
West Yorkshire Police were called in after a sheep was slaughtered and four horses slashed at farms and stables near Leeds.
The sheep's throat was cut and the horses suffered serious wounds which needed veterinary treatment.
Sergeant Simon Harrison, who is leading the investigation, said: "I do have to keep an open mind, but until I get evidence to the contrary it remains a possibility that they are linked to pagan rituals."
In the first incident, a horse grazing at stables near Wetherby was found on 16 June with a deep wound to its shoulder.
The same weekend, another horse suffered a similar attack at a farm between Collingham and Harewood.
On the following weekend, at the time of the summer solstice, the ewe had its throat cut in the same area and two horses were slashed at stables near Bramham.
The attacks in West Yorkshire come in the wake of similar incidents in South Yorkshire and Derbyshire.
South Yorkshire Police launched an undercover operation in the Fox House area of Sheffield to coincide with the summer solstice.
A police spokeswoman said: "Incidents include physical, and in some cases sexual attacks on horses and are accompanied by what officers believe to be cult practices such as stone circles."
No one has so far been arrested as a result of what South Yorkshire Police are calling Operation Equine.