Beef is very difficult to digest, I'll get that off right now. It takes a bit for beef to go bad, just a testament of how difficult it is to break it down, so would be a bad choice to feed to a problem feeder and could make matters worse.
Chicken is a better alternative, and since corns do eat fowl out in the wild once in a while, they may take to it better than they take to mice. However, Salmonella could be a problem, since a weak snake won't have the ability to control salmonella population in the gut, and it may end up being a bacterial bloom.
Although a little difficult to obtain, fresh mouse placentas have worked wonderfully for me to get a problem eater to eat (tons of vitamins and easy to digest, what more could you ask for?). Getting one is the tricky part, you need a mouse that's in labor, and you need to wait for it, but multiple placentas should come out during the entirety of the mouse's labor (just don't bug her too much or she'll stress and die on you). Just go in with a pair of tongs or chopsticks and nab one before she eats it.
Another thing that's worked are mouse livers. Mice have biggish livers, just make an incision in the stomach, and you'll see the big maroon thing, cut it out neat as you can and in one piece. Has a very similar effect to the placentas and more food. This needs to be fresh from a fresh killed mouse, as old livers tend to have a bit of decay and lack the slippery smoothness and the smell required for a good feeding response.
-Lemur 6
I was thinking that it might help out problem feeders to start eating and what not.
