As a (probably controversial) counterpoint, I'm not so sure that life in a state of nature is much better than life on a factory farm. The math of making it in the natural world is brutal: a stable population size means that, on average, only two of the offspring that an animal produces will ever become reproductive adults. You know that cute string of ducklings following their mother around? Statisticaly speaking, almost every one of them will be mauled, starved, or frozen to death.

That being said, I still believe that we have some kind of a moral obligation to provide the animals in our care with a decent quality of life.