The three enemies: damp, rodents and time
Stored chicken feed fails in three ways, and each one makes hens ill or leaves them eating dust. Damp feed grows moulds, some of which produce toxins that damage hens' livers and laying long before the feed looks dramatically bad. Rodents and wild birds do double damage — eating the feed and contaminating what they leave with droppings and urine. And even perfectly dry feed quietly loses its vitamin strength with age and heat, so a bag stored since spring is a poorer ration by autumn however good it looks. A storage system has to defeat all three at once.
Bins, lids and where the feed store lives
The workhorse solution is a galvanised metal bin with a tight, heavy lid for each feed type — metal because rats chew through plastic eventually, tight because mice need a gap of only a few millimetres, heavy because a bin raided by a determined badger or knocked by a goat teaches the lesson expensively. Raise bins off the floor on blocks or a pallet so damp and condensation cannot creep up from concrete, and site the store under cover where rain cannot drive in and summer sun cannot bake it. Decant each new bag into its bin on arrival rather than storing in the bag, and keep different feeds in different bins so layer pellets never get scooped from the chick-crumb bin. Sweep the store weekly; spilled feed on the floor is an open invitation that undoes the bins' good work.
Rotation: oldest first, every time
Feed should flow through the store like a queue: the bin is filled, emptied right down, and only then refilled, so no ancient layer of pellets lives at the bottom forever. If you run two bins of the same feed, finish one completely before starting the other. Note the delivery order on the bin lid with chalk or a tag — memory is a poor stock-keeper across a busy season — and buy in quantities your flock will finish while the feed is still fresh rather than stockpiling a bargain the hens will still be eating months later. When a new delivery arrives smelling musty or with a torn, damp-stained bag, reject or quarantine it at the door instead of binning it over good feed.
Knowing when feed has to be thrown away
Some judgement calls are not calls at all: feed that smells musty or sour, pellets clumped or caked by moisture, anything with visible mould, webbing from stored-product moths, or feed that has been flooded or leaked on gets thrown out entirely — the loss is a bag of feed, not a flock of hens. Droppings in an open bin mean the uncovered top layer goes too. If hens suddenly leave feed they normally eat, treat the feed as a suspect before treating the hens as ill. Write the bin order and the throw-away rules down in the feed store itself, so whoever opens a bin works from the note in front of them, not from a guess. With KinsLe Family Sharing, a relative you pick can open a hen's profile directly.