When any motor truck, truck tractor, or trailer is operated upon the public highways of this state carrying a load in excess of the maximum prescribed under the provisions of section 39-12-03, 39-12-05, and 39-12-05.3 or other maximum weight limitations prescribed by law, the load must be reduced or shifted to within such maximum limitations before being permitted to operate on any public highway of this state; provided, however, that any such vehicle carrying a load of livestock is exempt from the limitations prescribed in section 39-12-05.3, relating to the carrying capacity of any wheel, tire, axle, or group of axles when excessive weight is caused by a shifting of the weight of the livestock. All material unloaded as required by this section must be cared for by the owner or operator of such vehicle at the risk of such owner or operator.