Custom Livestock-- breeding Custom Entities

The title just about explains itself: I've never found a plugin that enabled the creation of Custom Livestock. In an ideal world, I'd be able to have a custom Cow named 'Unicorn', that could be bred with another Unicorn using 2 of a custom item--'UnicornFeed'--to produce a 'Baby Unicorn' which grows up in X amount of time. Ideally, you could customize the results of shearing the entity, or using a bucket on the entity, and so on; maybe just customize the result of any sort of a right-click...

Custom Livestock-- breeding Custom Entities