Treasure chest contents - new content in old world after upgrade?

Question

So, yesterday I've installed Minecraft 1.6 "Horse Update". I tamed my first horse and now I'd like to obtain a horse armor. I've read Horse Armor is spawned only in treasure chests.

Around my home there's a bunch of dungeons I still need to explore, and they surely contain some treasure chests. I've got most of the surface above them explored though.

I'm fairly sure I can't expect the armor to appear in chests I have looted already. Now what about the rest? Did the chests under the chunks I have explored spawn already, with predetermined (pre-update) content? If I go exploring some new chunks, will their chests spawn the armor, or will they contain the old loot as pre-determined by the world seed when generating the world on startup?

Answer 1

Chests will have been spawned with the loot already generated inside them when the chunk was generated, so any chunks that already exist will be unable to contain new items. But, new chunks will be generated according to the rules of the new version of Minecraft, so horse-related items will be able to spawn inside chests. Head out in a direction you haven't gone far before, and go exploring!

Answer 2

Only chests in newly generated chunks can contain horse armour. The seed is not associated with the version of Minecraft initially used to generate the map.