Be careful with cat and dog foods. They are super high in sodium. Not something you want to feed very much or very often. I would go with canned tuna personally.
I have mine on flock raiser all year long, it already has higher protein and they come through molt just fine. I would also be leary of giving them food designed for another species. Nutritional needs vary so much across species. Of course, my chickens are all over my spilled horse grain every morning. That hasn't done them in so far, but it could.