Shortly after installing pre-release, many of my chickens, pigs, and sheep had escaped their enclosures. I made all the fences higher and then bred a bunch of them to see if it worked, but even the baby animals appeared outside the fence after breeding. My cows have iron bars on top of stone instead of wooden fences and do not seem to be affected.

Note: they don't just seem to phase through the fence, they're actually getting through. You can interact with them on the other side.