A horse had to be put down after it was beaten with hammer in a field.
The animal suffered injuries to its face and legs in Stockport, Greater Manchester, shortly after 8pm on Friday December 30.
The attack took place in a field off Brindale Road in Brinnington.
Pc Louise Butterley, from Greater Manchester Police, said: "This was a vicious and despicable act on a defenceless animal.
"How anyone could harm a living thing is beyond belief. The pain the poor horse must have endured is unthinkable and I'm determined to find the person responsible for this sickening offence.
"No-one we have spoken to saw the actual attack take place and I would urge anyone who has any information about it to please contact police."
Information can be passed on by calling 101 and quoting incident number 1947 of 30 December 2016.