A Shetland pony was bludgeoned to death with a metal pole and its body left on wasteland.
The pony's rear legs had been tied together with rope and the animal was tied to a metal gate off Lyde Road, near Pen Mill Industrial Estate, in Yeovil, Somerset.
Dean Reddin who owned the pony, called Paddy, said he was "disgusted by the attack".
RSPCA inspector John Pollock called it "horrific and cowardly".
Mr Reddin said he kept Paddy in a nearby field.
"Paddy was a rescue horse and when I first got him he was really thin so I fed him up and he would happily graze in a field with my partner's horse Bailey," he said.
"I just can't understand why anyone would want to do something so horrific to a defenceless animal."
Bailey has been moved to a place of safety.
Police are working with the RSPCA to find who is responsible.