As far as I know, animals dont chnage their % protein based on the %protein they eat. Meaning. you can feed a ton of protein and it might grow faster thanif it was shorted on protein, but most creatures are preset on how they grow and what they will become. Only a few livestock have pushed the limits with some sucess: hogs and chickens. Others are beef, lamb and rabbit. Again, meaning thru selection certain varieties have excelled ( due to selection) more than other varieties.
Sorry if this is boring. ANimal Science background.
I buy bran from the feed store in 50 lb bags. rebag it and freeze it. Cheapest source of bran.
As for using dogfood, realize what you use is what you get. Dog food is cheap for a reason. It is by products. Usually vegetable protein is the cheapest protein ( compared to meat source) so is widely used. ie talapia .
Higher protein diet might increase the rate of growth but at some point it becomes a waste of money as the protein is used for energy and not making protein on the mealworms. Was going to say " meat " or " muscling" but somehow that just didnt sound right. lol
Unclekb-- yeah, great way to teach. My kids grew up on a breeding far, so knew and saw all manner of "production" activites including looking at "swimmers" under a microscope. I remember he was so little I had to lift him up to look in the scope on a table. lol Never too early to learn the science of stuff.