I'm playing on a multiplayer server on snapshot 15w32a, and my animals
(including sheep, chicken, and sitting tamed wolves) are despawning whenever I leave them at home.

I have not experienced this problem in any of the previous snapshots for 1.9, and I know that animals do not despawn in any versions after 1.8. Especially not tamed wolves.

It seems very unlikely that the animals were killed or wandered away, so i'm pretty certain that this is a bug.

I replicated that problem soon after it happened the first time.
With no other players nearby, my sitting tamed wolves disappeared, as did all my fenced in livestock, after i wandered several chunks away. This occurred both times and there were no other players nearby nor any other signs of player tampering.