USDA inspectors require bedding to be present in hog trailers. To cover a standard trailer with 1 inch of bedding 6 bails are required. In warm weather to much bedding can be detrimental to the pigs in transit and it was found that no more than 3 bails is required to keep dead on arrival rates down. In winter it was found that to much bedding would freeze after the first load of pigs and become dangerous to the next loads of pigs causing injury and death rates to increase.