I certainly take my pigs out to enjoy the grass when the weather is nice, but they stay inside when I can't supervise them (I've seen cases of hawks taking pigs, raccoons and coyotes breaking into hutches, even people stealing them or doing cruel things!).
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry