Well, you knew the answer when you said "it depends!" It depends.
It depends on how many goats are eating from that bucket, too. It depends on how many bugs the hens are getting in their diet. It depends on whether there is snow on the ground and it is their only protein or if they just got a big batch of scraps from making catfood. It depends on how hot or cold the weather is. I am always making adjustments.
I feed the poultry by scattering the grain twice a day and watching them to see when they are full, making sure the stragglers have a chance to eat. I don't leave food out unless we will be away at feed time, then I dump too much grain on the floor of the coop where the goats can't get it.
I feed sprouted oats/barley in the morning and whole corn (not soaked or sprouted) in the afternoon. No reason for that order other than convenience. I am here every morning but often in winter I don't get home from work before dark, and dry corn is easier for someone else to feed for me, or for me to leave on the coop floor.
I just know that I need to start a new bucket by the time the sprouted pail is at a certain depth. Sometimes I miscalculate or simply forget and I end up feeding soaked but not sprouted grain for a feeding or two, or even dry, unsoaked grain. No big deal. They will make up for it in the next feeding by eating more of the grain when it reaches its peak of protein.
I also don't worry if the sprouts get a bit too long, but that rarely happens. I've only lost a bucket to slime on very rare occasions, maybe once a year? I no longer let them get so long that they matte or get entangled.
I'd say I usually start around 3 to 3.5 gallons of grain every.....um......er......3-5 days? For 30 birds including two turkeys and a guinea and one or two goats. It is going up right now because I just started feeding five of my big goats grain once a day and will work them up to twice a day because they are all losing condition due to my last batch of hay, at least until the pasture really comes in. I normally only grain on the milking stand, for the most part, and temporarily to make up for certain batches of hay. It looks great but they are suddenly looking quite thin after a couple of weeks on it. C'mon, pasture! Grow!