Tin or aluminum can, rusted? Lots of haying in ditches is done around here, and it's not unusual to find deteriorating pieces of beer cans or tin cans thrown out windows in hay bales or even discarded pieces of farm equipment. They range from still quite hard to flaky and crumbling with rust. Where do you purchase your bedding? If it's from a local farmer or something, it might simply be road trash and debris.