Never even heard of that. I’d be inclined to call the USDA and see if it’s actually them. And maybe casually mention guard dogs in the conversation so they know they can’t just traipse in.
If it really is them, demand a warrant. Have an attorney’s number handy. Maybe even run the situation past an attorney before the inspectors get there.
It was real. She called the USDA and eventually got the right person. She told them in no uncertain terms that they weren’t welcome on the property and her lawyer would be sending them a letter stating such.
In the pamphlet that arrived with the letter we parsed that they are looking for ‘invasive species’ and ‘important ecological participants’ (ie endangered species).