Potion effects becoming permanent when mobs are bred

Baby mobs should permanently have the status effects that their parents had when the baby was conceived. This could be stackable, but only to a limited extent. This would add great new use for splash potions on single-player worlds, and create an exciting new reason for players to interact with the mobs of the world. I think this already exists as a bug for horses, unless it has been patched or implemented as a feature since I last checked.