My youngest, now 2.5 years old received a Highland cow family (Schleich -- awesome animal toys) for Christmas, as his uncle has the real deal on his farm. He's playing with them on the couch right now, and they're having quite the conversation (note: "na" is Boy#3's word for breasts/nursing):
Mommy Cow: "You Daddy cow? You haf penis?"
Daddy Cow: "I haf penis. You Mommy cow? You haf na?"
Baby Cow (in a squeaky voice): "I da baby cow! I haf penis! I drink na!"
I suggested the Mommy cow could nurse some of his other animals, too, but Boy#3 got really upset. He has now moved onto potty training his cow family.
Good luck with that one, Kid! ;)