Stating to feed game bird feed and nothing else is interesting, but not necessarily helpful to those of us that don't have that option. Where I live there are no game bird feeds available and the costs of shipping is so unbelievably high it's just not feasible. Right now we're feeding a mixture of laying mash and poultry premix, mixed to a protein percentage of 26 - 28%. Our birds also get meal worms, fresh greens, cuttlebones, and all the grit they need from their sand baths. We are looking into different types of natural feed stuffs for all our animals, things we can grow ourselves or trade what we grow with someone else to get what we need. Hopefully you will find this information helpful
Meal worms are very high in fat and should be fed as treats, cat food (even the organic kind) has many ingredients that are not suitable for birds.
But, there are many ways to get added protein, vitamins, and minerals in their diets that cost little to nothing.
Duckweed is one option - it is high in protein, has many vitamins and minerals, and is completely suitable for a bird diet. Not sure about where you are, but around here it grows everywhere. Every year we scoop a bunch of it off of the nearby sloughs and put it in our koi pond. It purifies the water for the fish, gives them needed shade, and they like to eat it as well. It grows very quickly and we just scoop handfuls off to feed the birds. Easily dried for winter use as well.
Zucchini - 28% protein and is a good source of vitamin C, vitamin A, folic acid, niacin, and fiber. It's also fairly easy to get free every year as there is always someone looking to get rid of their extra ones. Not sure why people grow so many if they don't eat them, anyways we shred them skin and all and feed fresh or dry for winter. Can also be frozen but not sure what that does to the vitamin/mineral content.
Dandelion greens are another option - Only has around 15% protein but very high in vitamins and minerals.
Chives - 27% protein and high in vitamin C (Our chickens, turkeys, and guinea fowl help themselves to the chives in our garden, the quail have shown no interest in it. I do not know, however, if they are suitable to be included in a diet for quail or not)
Comfrey (dried) - has 25 - 30% protein, also rich in vitamins and minerals, particularly calcium, potassium, phosphorus and iron, as well as magnesium, sulphur, copper, zinc, selenium and germanium
These are just of few of the ones I can think of, do a search and you can find many more, but make sure they are suitable for birds before adding them to their diet.
PLEASE NOTE: The above is strictly for informational purposes and as examples only. PLEASE thoroughly investigate any and all feed ingredients before deciding whether or not YOU choose to feed them to your birds.