Most feed stores that do not have very many in the area that want a certain type feed, do not keep it in stock because they have to order a minimum amount.... or in the case of a mill than makes their own, have to make a minimum amount. If it is not sold in a reasonable amount of time, it can get "old" or even stale and musty. Our mill will make a 1 ton of some of the feeds, but then I get it delivered in bulk and have to have a 2 ton minimum for delivery. So I can get 1 ton of poultry and 1 ton of cattle feed. I also get a small discount if I give them at least 48 hour notice or get a minimum of 4 ton.... I will get the early order discount if I call ahead and tell them......Whenever you are headed this way the next time, I need 2 ton of such and such.... Sometimes it is 3-5 days.... but they give me a break since they can put in on a truck that is already coming this way. Most of the delivery trucks have 4-6 separate "bins" and they hold at least 2 ton.
But in the case of having it on the "floor" at the store....if there isn't enough call for it, it will get stale or even musty. So if you can get a place to order it for you, and take a minimum amount, and are a regular customer, they will be more likely to keep some in stock. Many places have to get at least a ton.... a pallet will hold up to 50 - 50 lb bags..... and many places that get it shipped in will have to get a minimum of a pallet. If they make their own, most "mixes/formulas" are based on a ton because many of the vitamins/minerals etc are added in small amounts......like 4 lbs per ton, 1/2 lb per ton, etc. It is often very difficult to break it down in less than a ton mix. If they carry the mix in 50 lb bags on the "floor" they are making up 1-2 tons at a time so that it is fresh for the customer.
Years ago, I was raising guinea pigs and had TSC order GP pellets in 50 lb bags. GP's do not make Vit C in their system and it has to be ingested from their food.... like humans. They did not carry it, so I asked and had to take 4 bags at a time, and then they found that there were a couple other people who would buy it. TSC is better about being able to order "partial pallets"... but it depends on the store manager too.