Might be worth getting the pig poo tested as well as the soil ... to see how much of the copper is coming out in the poo, and how much is actually being absorbed by the pigs ?
And the forage too .. how much is being absorbed by the grass etc.
I wouldn't risk it myself, and I have (copper insensitive) black sheep, only cos it sounds too complicated to work out without some professional help.

You need to know the levels of the other minerals in your environment too as they work together, some will prevent other minerals being absorbed and some will aid others. Like I said, way too complicated for lil' ol' me.
