How I got my pigs and cows all the way down to my WIP mine/farm/Thaumcrap/etc. level at my survival house on the Myranium Mindcrack server. Yeah, it's a little drab down there right now. I promise I'll give them some grass and do a nice mural for them on the walls.
Are there more efficient ways to get pigs and cows underground? Sure. Are there more fun ways to do it? HELL no.