HMMMM!
Naturally, there's "no way" that "manure" is being present in the same places as "hanging meat", and, of course, the "surface exposure" of meat is quite limited, compared with the meat muscle mass...(ie if you dug out a "cube" or "scoop" from within a loin or ham or shoulder, its plainly impossible for this to have been in contact with any form of anilmal excrement!) ("inside slices of pork roast, for instance!)
So if you can "rationalise" to that point, "wash" the "outside pieces" of your pork thoroughly before freezing and you are past the point of your objection....
You might also consider that the USA has no "quota" system...whoever produces the most, the cheapest, "wins", down there, so there's no "proof" that the pork you buy at your local A+P or Wynn Dixie or whatever is coming from the neighbourhood "stinky" plant...
The North American "appetite" for pork "ribs" is almost limitless, and yet the Danes consider this part of the pork carcass to be "inedible" (dunno why, but lets encourage them!) and therefor, the Chef that gave me a few classes advised that a "lot" of what we got was "frozen Danish ribs"...notice any "aftertaste" there? (of course, you cannot...the ribs are beneath the skin, as are the chops, loin roasts etc)
If you did, again, its in your "head"...or there'd be a simply MASSIVE die-off of people from e-coli bacteria in place and process...
Have you considered this, or "re-locating" your residence to get around this "problem"?
Lifter