I've used dog food, mostly by itself, for over 5 years now with no problems with production. You have to read the labels. I use one that has an 18% protien level and lower in fat. I've found that the cheapest dog food you can find (something you probably wouldn't want to feed to an actual dog) works best for rats. I use 'sprout' brand dog food that I get at Mills Fleet Farm. I've heard that the doggy bag brand that you can find at Tractor Supply also works well.