How well do pen fed bucks do when they are released out in a pasture?
Depends on what the breeder is doing to them in the pens. If they are injecting them with hormones etc they won't ever be what they are in the pen.
If not, and the pics listed don't look like that
, you will see a small drop the first year and an increase after that.
Caveat: some of those 2 year olds you won't see any drop at all in. In fact you'll see and increase. They grow a LOT between 2 and 3 and they'll be fine and make you happy on year four.