I would probably try to go wider instead of up, because some pigs don't use ramps. We recommend a 2.5 as a bare minimum for 3 males, and try to talk people into a 2x6 whenever possible.
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