Respawnable Animals changes the spawning mechanics for all animals to be similar to those of most mobs such as monsters.
All animals are now able to Despawn and Respawn as they please. They will no longer only be spawned once upon world creation. This once again enables plenty of mechanics from the Beta and Alpha days of Minecraft, most notably passive mob farms.
In vanilla Minecraft all mobs with the persistence property will not despawn. To prevent a few game mechanics from breaking, animals now automatically gain Persistence when ridden by the player, named with a name tag, bred or born as a result of breeding, and when tamed by the player. All mobs can additionally become persistent when spawned from a spawn egg or the
/summon command, although this specific behavior is disabled by default.
In case the changes to animal spawning mechanics break the behavior of another mod, a Blacklist for individual animals can be found in the config file.
The behavior of Respawnable Animals is controllable on a per world basis via the use of a custom
persistentAnimals game rule. When the game rule is set to
false this mod will take effect, which is the case for every world created with Respawnable Animals installed.
To prevent animals from vanishing out of farms in precious old worlds, the game rule will automatically be set to
true for those. Enabling Respawnable Animals retroactively simply requires updating said game rule by executing
/gamerule persistentAnimals false. In a survival world with cheats disabled the command can be run by temporarily hosting a lan session from the pause menu with cheats enabled.
Respawnable Animals runs purely on the server-side. It even works when using a vanilla client to connect to a Forge server having this mod installed.
Developing Respawnable Animals was helped and inspired by: