This would be great, and would force property owners to tweak their animal mix.
For instance, after populating the streets nearby with MANY chickens, I finally set the chickens in my backyard free.
So I could have less depressed butterflies.
~CTP
I think the problem is that there's no input to chickens. Pigs need to be fed, and butterflies need to be re-hatched periodically. Chickens just generate grain out of nothingness, so a grain collector would be an excuse for utterly free grain. As it is, I can drink 2 gurly drinks and squeeze 1000 grain in almost no time.