For the horse scoops (three quart but hold about 2 1/2 quarts) that I use- I would estimate about 10 scoops per 40 lb bag. This is just a guess and may be off.
I put my feed into 5 gallon buckets to keep the mice out. I'm just getting back in, and it's been 2 years since I've had girls. It seems I could get a 50 pound bag of feed into two 5 gallon buckets.