21 C.F.R. § 510.7
(a) A new animal drug intended for use in the manufacture of animal feed shall be deemed to be unsafe unless at the time of its removal from the establishment of a manufacturer, packer, or distributor of such drug, such manufacturer, packer, or distributor has an unrevoked written statement from the consignee of such drug, or a notice from the Secretary, to the effect that with respect to the use of such drug in animal feed the consignee:
(b) The requirements of paragraph (a) of this section do not apply:
[40 FR 13807, Mar. 27, 1975, as amended at 64 FR 63203, Nov. 19, 1999]