I have a cat that I feed Orijen and she doesn't get hairballs, but soon I'll be taking my sister's cat who gets hairballs unless he's fed a special hairball formula. She's feeding him Wal-Mart brand stuff, though, so I'd like to switch to a high quality food like Orijen, but I don't know if that means he'll start getting hairballs again. Is there a high quality hairball formula? Is it possible to have one that's grain free? Thanks.