I have recently been feeding my birds dry instant oatmeal with yogurt( I use Bulgarian yogurt) I'm sure you can use already cooked oatmeal too! Please post your recipes, of heathy or spoiled flock treats!
Definitely BOSS, they all go nuts for that...but it's expensive. My favorite healthy thing to give them is fermented feed. I use soy free Scratch and Peck feed, Bragg's Apple Cider Vinegar, and a little juice from my homemade sauerkraut. I add those things, water to cover, let it sit for 3 days and feed them!
Don't cover anything fermenting tightly. If it is a jar, it could explode.
The protein will be the same, what is there may be more bioavailable. Ferment doesn't create protein.
8% is about right for scratch, possibly as high as 10 depending on what seeds are in it.