These terms all refer to killing animals. Some have implications about the nature or purpose of the procedure:

• euthanase: to subject to euthanasia – literally ‘a good death’; often used to emphasise that the animal was killed humanely
• slaughter: often used to mean killing of an animal to produce meat for human or animal consumption.

Cull and sacrifice are best avoided because they are euphemisms. Of the other terms, the one chosen should be used consistently throughout a document to avoid confusion.