(1)    The Babcock or ether extraction tests shall be used to determine the milk fat content of milk or cream purchased by or sold to dairy plants, but the department may issue rules permitting the use of other methods or devices for testing and determining such milk fat content.

   (2)   Each sample used for testing shall be representative of the milk or cream from which taken. Composite samples shall consist of representative samples taken during a period not exceeding 16 consecutive days. The unused portion of tested samples shall be retained not less than 5 days after testing to enable retesting by the department.

   (3)   All purchasers of milk or cream from the producer, when using such milk fat tests to determine the value of any milk or cream received or bought by such purchaser, shall, when paying for such milk or cream, include an itemized statement to each patron showing the daily number of pounds of milk delivered, the total amount of butterfat content or test, transportation costs, and other charges and deductions for the period of time for which payment is made; except that the daily weights need not be shown on such statement if weight slips are furnished daily to producers.

   (4)   Whenever milk is sold under an agreement, express or implied, that the value of the milk shall be determined by its proportion of butter fat, the price to be paid shall be based on a 3.5 percent butter fat standard.

   (5)   To insure the accuracy of the milk fat tests prescribed herein the department shall issue rules governing the collection and care of samples, the conduct of tests and the keeping of test records.