I usually switch around with treats to keep things interesting. Sometimes I use Zukes, sometimes Bil-jac, sometimes homemade, sometimes just cheese or turkey hotdogs. Although, with a highly food motivated sheltie, I'm not sure how necessary that is. I am a little worried about Purina owning Zukes, but I probably won't stop buying it until I find or hear about a big change in ingredients or manufacturing. Fortunately, there are quite a few options for me since my dog isn't food sensitive or picky.
I'm very grateful this forum keeps me informed!
Also, my recent Zukes purchases I haven't really paid attention to the bags for any differences. I'll try to remember to check when I get home.