With the storage on a farm you are right to be concerned about mice. We personally would not keep anything that will help them build nests/keep them warm. Paper and therefore the kitchen towel is classical 'go to' for mice. Not meaning to sound a smart arse but whenever we leave it for more than a few weeks we have a simple system of decanting everything into 'really useful boxes' marked up with what goes where. Mice also pee a lot to mark their territory. Blimey sounds a bit OTT but it works for us, we use it as a normal procedure.