The Rat Upgrade: Animal Breeder will allow a rat holding food to breed animals. The rat's command needs to set to "Harvest" in the Rat Menu to breed animals. Rats will pickup food items from chests or like storage that it is bound to using a Cheese Staff. Like all Rat Upgrades, it can be applied to a rat by placing it in the upgrade slot in the Rat Menu.
Crafting[]

Crafting Recipe for Rat Upgrade: Animal Breeder
Behavior[]
Rats with the Rat Upgrade: Animal Breeder will attempt to feed the closest animal with the corresponding food not in breeding mode. If there are no animals available to feed because of breed mode, the rat will wait till one animal is no longer in breed mode.
Other mod interaction notes:
Animania - Rats will feed the closet animal from this mod, however it will not put the animal into breed mode. In consequence, rats will still attempt to feed the same closest animal with food until supply runs out. It is not recommended to use this upgrade to breed animals in the Animania mod.