Minecraft wiki entry for Development_versions, associated text: For all horses, HasReproduced, Type and Saddle tags are removed.
ChestedHorse and Items tags now apply only to mule and donkey.
SkeletonTrap and SkeletonTrapTime tags now apply only to skeleton_horse.
Elder tag is removed from guardian and elder_guardian.
ZombieType, and IsVillager tag is removed from all zombie types.
ConversionTime and Profession tags now apply only to zombie_villager.
SkeletonType tag is removed from all skeleton types.
Pumpkin byte tag is added to snowman.