I have spawned horses from eggs in creative mode. The horses are inside a 10 x 12 pen of double-height wood fence rails. The horses are not tied up with rope and they can be wild or tamed. While playing the game, in both creative and survival mode, when I have moved away from the pen about 150 blocks, then return, the horses can and do despawn. If the horses are wearing armor, they do not despawn. This makes breeding horses a bit of a problem (as in nearly impossible). This is happening without my logging out and back in to the game.
Linked issues
Comments

Kumasasa, I am fully aware that untamed horses despawn when the player leaves a chunk in single player, however, tamed horses, if they are wearing armor, have not despawned in my game at any time, and I have had a copy of 13w17a running since it first became available. I did have a tamed horse despawn, however, it was not wearing armor. I have not been able to replicate this behavior since I made the above report. All tamed horses, whether or not they are wearing armor, are not despawning, now, when I leave the chunk that they are in. This is not a duplicate of MC 13716, as MC 13716 reported that all horses were despawning, which was then confirmed as normal at this time, whereas, in my experience, I first had only horses that were not wearing armor despawn, and now only untamed horses are despawning. It appears to me that the bugs are being worked on, and fixes thereof, possibly pushed through the experimental loader, on an ongoing basis, as the dewpawning behavior is changing over time. NOTE TO ANYONE READING THIS: I SAID THAT "IT APPEARS TO ME . . ." This is NOT a statement of fact, as I am not affiliated with anyone who would have any "inside" information on this. [Do I dislike the rumor mill? Why, yes, yes I do.]
my tamed and untamed horse despawm even the tame horse with armor despawn
Same happened to me!!!! But it still had armor and then my armor and saddle and horse all got wasted and it was in survival so it’s not like I can just take another from my inventory. Also same happened to me with parrots and a dog and a cat! Super upset but I’m using a mobile device and I just got this so I’m not quite sure how to report a bug yet
Duplicate of MC-13716