Every person or agent or servant thereof engaged in the business of receiving or buying milk or cream on the basis of, or in any way with reference to, the amount of butterfat contained therein, or on the basis of tests made for official inspection or public records as determined by the “Babcock test” shall have the test or tests made only by a licensed tester who shall be responsible for the same and who shall keep a proper and permanent record of all tests made and a copy of such record shall be kept by the owner or manager of the plant.