This project has moved to Planet Minecraft.
Happy Animals encourages better treatment of farm animals by rewarding players with more drops the happier an animal is, and less drops the sadder an animal is. Cramming animals together into small pens will result in very sad animals, but giving them lots of space to move around in with blocks and plants they like will make them happy. There is a guide book that is given to the player once they tame an animal, or breed two animals, for the first time (or the next time after this data pack is installed) which explains how to care for the needs of each type of animal. This guide can also be created by renaming a book "Husbandry" in an anvil.
With this data pack installed, every breedable animal that has drops has a mood of either happy, content, or sad. Content animals drop the same amount of items as if this data pack wasn't installed. Sad animals drop less than the normal amount of loot, are lethargic, and disinterested in breeding. Happy animals drop up to twice the normal amount of loot. Happy animals display sparkle particles every so often. Content animals don't display any particles. Sad animals display thundercloud particles every so often. Animal mood naturally gravitates towards contentment when within their normal habitat.
With this data pack installed animals that don't already have a healing item can be healed by feeding them their breeding item(s).
This data pack is not compatible with any data pack that changes the loot tables of breedable animals.
More information about data packs and how to use them can be found on the official Minecraft Wiki.