StodOne
Proso millet is sort of the standard "white" millet. It's fine for finches, but not by itself - its low in either A or B vitamins, I forget which. I'm leaning towards B vitamins being the lacking component in millet.
My guys are pretty picky eaters when it comes to seed. Most of the extra stuff you find in the finch mixes (and not in the budgie/parakeet mixes) they absolutely refuse to eat. This includes pellets, pieces of dried fruit, rape seed (tiny little round black seeds) and flax seed.
Flax seed, it turns out, has something bad in it anyway so I've given up on it. They utterly refuse to eat it.
After several months of observation and reading and figuring out what is locally available to me, I've settled on the following regime:
Budgie mix. I had been mixing it with finch mix 2:1 (budgie to finch) but I've decided there's really nothing in the finch mix they will eat or that they NEED to eat, so I'm going straight budgie mix for their staple seed from now on.
Budgie mix consists of 3 or more different types of millet, canary reedgrass seed, and oat groats. My guys eat all these seeds without problem. While not perfectly balanced, its pretty good as-is and I make up shortfalls by being sure I'm using a good vitamin in the water and plenty of mineral/calcium sources.
In addition to the budgie mix, I have the following in the cage at all times:
sunflower chips - They eat regularly.
Chia seed - They eat regularly but lightly.
nyjer seed - this, in particular, they rejected for months but have recently taken to eating it in small amounts.
I rotate through the following - 2 of these will be in the cage at any given time:
flaked red wheat
oat bran
wheat bran
whole oats (in the hull)
canary reedgrass seed
hulled hemp seed
cracked wheat
sesame seed
Oat and wheat bran, it turns out, have something bad in them as well, so I only give them a little bit when sesame seed is on the rotation. I mix some bran in with the sesame seed. Then it sort of self-limits their exposure so they don't get too much of it at any given time.
I also got pearl barley and buckwheat groats but the pieces are too big and I need to find my spare grinder so I can grind them a bit smaller.
I have society finches and they are opportunistic breeders - I believe Zebra finches are also opportunistic breeders, eg they are not deeply affected by day length to trigger breeding, but are very affected by availability of resources, eg - FOOD.
Society finches is what I've been reading about lately, but if Zebra finches are ALSO opportunistic breeders - and I'm pretty sure they are, I swear they're the rabbits of the avian world - a lot of this probably also applies.
So if you don't want them to breed, put them on an austerity diet. EG just give them greens, fruits, and the staple seed which is budgie mix for me, and some egg food from time to time, and all the minerals especially calcium in cuttlebone, mineral blocks, something like the ABBA mineral mix, crushed sterilized egg shells, oyster shell.
However apparently (if what I've been reading recently is correct) they won't go into a full molt until after a breeding "season". So postponing breeding indefinitely, if its even possible, is probably not ideal. They need to shed feathers to get rid of damaged feathers.
I did notice a significant decrease in breeding behavior when I started covering the cage at night, but that may have been coincidence. Perhaps they were already done with their evil breeding tricks by then, LOL! So - daylight length may still have SOME effect on even opportunistic breeders. Or - maybe not. I've not come across anything definitive on that score yet.
For now they seem to be doing ok on the budgie mix plus supplementary seed listed above. Plus greens and egg food on occasion.
If you start with a good budgie mix, you're most of the way there already. Proso millet as a seed supplement or in the budgie mix is fine, but not as their main staple seed.