My stored maize and grain have a musty smell but no visible mould, is it still safe?

A musty or stale smell is an early warning, even when you cannot see mould yet, because the smell often comes from mould growth and grain heating that has started in the damp centre or bottom of the heap before it is visible. It usually means the grain went in too moist, picked up moisture from a damp floor or leak, or was sealed while warm. Take it seriously, because mould growth on grain like maize can lead to toxins such as aflatoxin, and musty grain can lose grade or be rejected and is not good to feed heavily to animals. First, open and inspect the lot, especially the bottom, centre and any spot near damp walls or a leaking roof, and look for caking, discolouration, warmth or webbing. Aerate and sun dry the grain to safe moisture, then cool it before resealing, and fix the moisture source. Keep clearly mouldy, caked or discoloured grain separate; do not mix it into good stock to hide it, as testing will catch it and downgrade the whole lot. If the smell is faint and from a small surface area caught early, drying and aerating may recover most of it; if it is strong and widespread, get it checked before eating or selling. Verify safe moisture and any testing access with your KVK.