The cheapest kind (or what you already feed your dog)! Let me go back to my post: I "dumb down" the protein content with other non-dog food items. I currently use something called "high performance" dog food from HEB in my chow, which is the prominent non-Walmart version of a grocer in San Antonio.
I guess your response begs the question, "Why are you concerned with certain brands of dog food?" What are you worried about your roaches eating? Let me know!