Obviously those with a large number of pigs to feed are likely to buy their feed in bulk. Either blown into a building or some type of hopper. This allows them to considerably reduce their feed costs.
For those with a couple of pigs, the necessary storage requirements mean they can’t take advantage of buying feed in any great quantity. However, some feed merchants charge more per bag for buying one or two bags, than if you buy say four or six. It is worth asking if your feed merchant does this. Another option might be to ask for a half or tonne rate, and then see if you can buy up front but only collect weekly what you can manage. This take advantage of any discount but means you don’t have to worry about transport or storage of more feed than you can handle.
You can buy metal feed bins to store your feed in or dustbins are useful. Leaving bags where rodents can take advantage is not only a health risk to you and your pigs but wasteful.
Unwanted pests particularly rats but also birds soon know when a free meal is available and when you feed in hoppers ad lib it is a nuisance you will have to deal with. Be careful when using poison especially packets as rats like to drag potential feed back to their nest and can spill poison. Blocks nailed onto pieces of wood, which you can put where other animals can’t reach them or into bait stations are better.
Why not consider a couple of cats? You could give a couple of feral cats a new home and let them deal with pest control for you.