Of course, the slaughterhouse you mentioned is illegal. You said the police in your county were working with them. I think it's just an individual who is in cahoots with them. I'm afraid the heads of the public security bureau have all benefited from them. This will be difficult. You can report their illegal behavior to the administrative department at the next higher level of your local public security bureau. At the same time, in the face of criminals, you should refuse to be afraid of them, so that they can still kill people. If there is any conflict, it should be reported in time. If not, you can ask local media reporters for help in obtaining evidence or really ask the municipal legal column group for help.
I am an animal husbandry worker, and I really hate their behavior. These are just my buddy's personal thoughts.
You can also consult with a law firm.