(a) The Secretary may refuse to register any commercial feed not in compliance with the provisions of this subtitle. He may cancel the registration of any commercial feed subsequently found not to be in compliance with any provision of this subtitle. However, no registration may be refused or canceled until the applicant or registrant has been given opportunity to be heard before the Secretary and to amend his application or the Secretary may allow the feed to be processed so that it complies with the requirements of this subtitle.

(b) The Secretary may permit a change in the guarantee of either chemical or ingredient composition of a registered commercial feed, if there is satisfactory evidence that the change would not result in a lowering of the feeding value of the product for the purpose for which it is designed.