> and they are absolutely in every way possible better off than a bison wondering the Serengeti

Why is that, though? I would reckon that most animals on the Serengeti (not Bison, mind you) live out their average lifespan. Sure, some percentage of them are eaten or die to drought, but there is a reason that their average lifespan is 15--20 years, or whatever it happens to be. Compare that with the 5--6 year average lifespan of a factory farmed animal. It is hard to give you a more detailed argument without understanding the real reasons behind your value judgement.