A processed pet food shall be deemed to be misbranded:
(a) If it purports to be or is represented for special dietary uses, unless its label bears information concerning its vitamin, mineral, and other dietary properties as the department determines to be, and by regulations prescribes as, necessary in order fully to inform purchasers as to its value for those uses.
(b) If it bears or contains any artificial flavoring, artificial coloring, or chemical preservative, unless it bears labeling stating that fact. To the extent that compliance with the requirements of this paragraph is impracticable, exemptions shall be established by regulations promulgated by the department.