The state milk board is hereby designated as the official rating agency. At least biannually, or as often as necessary, the state milk board shall make an official rating survey to determine if there is appropriate and effective enforcement of the standards and provisions of sections 196.931 through 196.953 and such other surveys as may be necessary to assure enforcement of sections 196.931 through 196.953 throughout the state. Unsatisfactory conditions shall be deemed to exist when a rating below the minimum acceptable rating established by the state milk board is found by the official rating survey. Violation of sections 196.931 through 196.953 shall be deemed to exist when the unsatisfactory conditions causing the rating to fall below the minimum acceptable rating are not corrected within ninety days. The minimum acceptable rating shall be ninety percent for the pasteurized milk supply as determined by rating methods recognized by the United States Public Health Service Food and Drug Administration. The state milk board shall promulgate and adopt a single method of making official rating surveys of all milksheds. Official surveys shall be made by a method substantially equivalent to procedures outlined in United States Governmental Printing Office Publication Number 678, titled “Methods of Making Sanitation Ratings of Milksheds”.