Having visited the snack vendors in Cool Ranch and MooShu, I'm a little disappointed to find that they sell the same rank 1 and 2 snacks as are available in Bestia. Shouldn't the higher level worlds have access to higher level snacks?
I'm guessing that they want you to use your Companions go Pet Wranglin', do Pet pvp in the Petathalon in Circus Maximus, and find the drops from Bosses and other opponents. If all you had to do was buy the correct the snacks for pet training, that would be too easy.