Two sheep were seriously injured during a dog attack in Crick on Saturday, with one of the animals having both of its ears bitten off.
The attack occurred sometime between 6.15pm and 6.45pm on October 25.
Another sheep was also seriously injured in the attack, which is believed to have been carried out by two lurcher-type dogs.
It is believed that two men took the dogs into the field and officers investigating the attack are keen to trace them.
It is an offence for a dog to worry livestock and both the owner of a dog and the person in charge of it if they are not the owner, can be prosecuted.
Anyone with any information about this incident, or who has been a victim of livestock worrying, can call Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555111.