Well, of course any feed store or vet will maybe recommend Purina. My cats eat Purina wet food, darn. Have tried others. I buy the best dry food, not Purina.Look at the Kent Feeds website; their dealers carry Blue Seal feeds, which include some that don't have GMOs.
I personally have never had a problem with Purina; it was one of the brands recommended by the avian specialist veterinarian.
Our local feed store put on a free clinic for people who want to raise chickens. Found out it was Purina that was putting on the seminar. So, the only thing we got out of it was video's from Purina.
We left and bought non GMO from our local poultry farm.