This morning, just before leaving for work (5:00 am) my suspicion is confirmed. The bottom corner of the grain bag in the garage has not been kicked loose and open, it has been chewed. We have had little field mice or whatever in the garage before, but this is the first time since I have had a grain bag in the garage. Frantic 10 mins shovelling the grain into Tupperware-type containers and the like and even a brush up of the loose grain. Quick eye-ball check on the grain as it gets transferred, via a JD Sports mug, for rodent droppings. Of all the additives to beer over the last n thousand years, perhaps mouse s**t is the least appreciated.