Because i feed with lots of other things i made a simple mix, but if i would do today i would add the garlic, that i dorgot
1 beef hearth (clean it from fat as much as possible, you just want the meat)
1 carrot (boiled) (it enhances colour and gives some more vitamins and minerals)
gely (i used the powder) enough to make it more consistent
If you have, add some vitamins and other things you might want, like shrimps, some white fishs, and garlic, very very important.
But as you see you dont need a big and dificult recipe, because it will be just a part of the diet. The industrial food give them what they need, this is just to boost their developement.