Iowa Admin. Code r. 21-61.15
Conveyances for transporting carcasses of animals must be provided with watertight bed or tank not less than 24 inches in depth; all metal or metal-lined and watertight at least 4 inches above the general level of the bottom of box or bed; endgate to be of metal or metal-lined, hinged at the bottom of box or bed and fastened firmly at top when closed; endgate to be provided with an effect on the inside to fit snugly over the end of the bed.
This rule is intended to implement Iowa Code section 167.15.