Hi.. protein levels much higher than 20% cause them to become scabby. The diets that they use in the laboratories which are ideal are 18% protein for breeding. Stick with the high quality dog foods that are 20% protein or lower if possible. I've used a recipe similar to Becky's for a long time and it works wonderfully.

I use lab style cages which have a food hopper built into the wire lid so that the food does not touch the bedding.