I have three stables set up in my world with horses for me and my friends who join me from time to time. Immediately after the update, we lost no fewer than four horses to despawning. They were tame, named, saddled, and a couple of them were even armored. They were in corrals with other horses, and just simply vanished without a trace. Unfortunately, I didn't have a written list at the time so I can't say for certain how many were lost.

However, I can say for certain that three horses were lost by me while I was testing them on a redstone hurdle contraption designed to test their speed. It's nothing elaborate, simply a track with pistons, redstone torches, pressure plates and lines of redstone, which I found on YouTube by OMGCraft and modified. The game crashed three times, and each time I lost the horse I was riding and its saddle.

I was in multiplayer at the time, hosting two friends in my world. One of them was also out riding on the occasion of two of the crashes, and lost both horses and their saddles without a trace.

I have stopped using the track while in multiplayer. Using it while I'm playing alone hasn't been a problem. I've tested no fewer than two dozen horses on it while playing alone with no problems whatsoever.