MRLang, for $15 you can also get 40-50lb hog food from most places. In my opinion it is a better chow for mice and rats. One big thing I don't approve of in doggy bag is the use of 'animal' products, and 'animal' bone. It does not specify what sort of animal is in there, or what sort of products are in it, so I steer away. It also feels greasy to me, because they spray the pellets with artificial and natural flavors to make dogs want to eat it (poor dogs!). The hog food doesn't have this, because i guess pigs don't care what their pellets smell like!
It also contains BHA which is a suspected cancer causing agent, and menandione, which has been linked to liver problems.
It's a personal choice, but these are my opinions on the two feeds.
King James, it looks like kent makes a 23% rodent food as well. Makes me wonder... Someone, somewhere out there is clearly having success with high protein, and there is a demand for it. But everyone I've ever spoken to that's put any thought into it, seems clearly opposed to using such a high protein level.