I'm playing on a vanilla survival server, and made myself an underground pig farm. I finally found carrots, and tried to breed my pair of pigs, but the babies seem to disappear after a while. I've made five or six piglets from the same parent pair. I was near one of the piglets at one point, and while I didn't see it actually take damage, I did spot pork on the ground after, which makes me think that they die when they grow up? I am unsure if this a is a bug... or is there some rule about how tall the enclosure for pigs must be? It's 1 block high in some spaces, and 2-3 blocks in others.
My adult pair seems to have survived just fine thus far.
Thanks for all the advice! I made the area much deeper, and it seems to have helped. Thanks for all the advice! I'd thought that adult pigs were only one block high, and thus that the 1-block wouldn't hurt.
I am pretty sure no one is killing the piglets - I have been the only one on when it's been happening, and it's a bit more of a friendly server than anything (my friends and I).