Sec. 666.100 Alternate Feeding of 
Different Medicated Feeds 
 
Compliance Policy Guide 
 
Guidance for FDA Staff 
 
This version of the Compliance Policy Guide replaces the version made available July 1981.  
The document has been revised to current CPG formatting standards, to update contact 
information, and to clarify existing language. 
 
Additional copies are available from: 
Policy and Regulations Staff (HFV-6) 
Center for Veterinary Medicine 
Food and Drug Administration 
7500 Standish Place 
Rockville, MD 20855 
https://www.fda.gov/ICECI/ComplianceManuals/CompliancePolicyGuidanceManual/default.htm 
 
 
Submit either electronic or written comments on this compliance policy guide (CPG) at any time.  
Submit electronic comments to https://www.regulations.gov.  Submit written comments to the 
Dockets Management Staff (HFA-305), Food and Drug Administration, 5630 Fishers Lane, Rm. 
1061, Rockville, MD 20852.  All comments should be identified with docket number FDA-2018-
N-3338. 
 
For further information regarding this document, contact AskCVM@fda.hhs.gov. 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Office of Regulatory Affairs 
and 
Center for Veterinary Medicine 
 
March 2019    Contains Nonbinding Recommendations 
Sec. 666.100 Alternate Feeding of Different Medicated Feeds 
 
Compliance Policy Guide 
 
Guidance for FDA Staff 
 
This compliance policy guide represents the current thinking of the Food and Drug Administration (FDA) 
on this topic.  It does not establish any rights for any person and is not binding on FDA or the public.  
You can use an alternative approach if the approach satisfies the requirements of the applicable statutes 
and regulations.  To discuss an alternative approach, contact the FDA office responsible for this 
compliance policy guide as listed on the title page. 
 
I.  Introduction 
 
The purpose of this compliance policy guide (CPG) is to provide guidance for FDA staff on the 
practice of alternate feeding of different medicated feeds.  In this document the term alternate 
feeding includes any separate feeding of different medicated feeds to the same animals in the 
same day as well as concurrent feeding of different medicated feeds. 
 
In general, FDAs guidance documents, including this CPG, do not establish legally enforceable 
responsibilities.  Instead, they describe the Agencys current thinking on various topics and 
should be viewed only as recommendations, unless specific regulatory or statutory requirements 
are cited.  The use of the word should in Agency guidances means that something is suggested or 
recommended, but not required. 
 
II.  Background 
 
Feedlots and other animal producers sometimes consider adopting the practice of alternately 
feeding different medicated feeds, both containing drugs which, if combined in a single feed, 
would require an approved new animal drug application.  One example of such an alternate 
feeding practice is feeding one medicated feed in the morning and another medicated feed in the 
afternoon of the same day, which is often referred to as AM-PM feeding.  Another example of 
an alternate feeding practice includes concurrent feeding of different medicated feeds during the 
same feeding.  These practices bring into question drug safety and effectiveness. 
 
III.  Policy 
 
The FDA does not accept the practice of alternate feeding of different medicated feeds.  This 
practice could result in above tolerance tissue residues, and if so, is a violation of section 
501(a)(6) of the Federal Food, Drug, and Cosmetic Act (FD&C Act).  Alternate feeding of 
different medicated feeds would expose the animals to unapproved drug combinations by 
enabling separately approved and fed drugs to get mixed in the animals digestive tracts.  Such 
practice also would violate 21 CFR 514.4(c), which requires substantial evidence for 
combination new animal drugs.  If an animal producer holding an approved medicated feed mill 
license practices alternate feeding, a violation of section 512(m)(4) of the FD&C Act occurs and 
2  Contains Nonbinding Recommendations 
subjects the approved medicated feed mill license to consideration of revocation proceedings if 
voluntary correction cannot be obtained. 
 
The FDA would not consider the one-time switch necessary to take the animals from one 
medicated feed to another as alternate feeding, even if the previous medicated feed was fed, for 
example, in the morning, and the subsequent medicated feed was fed in the afternoon of the same 
day. 
 
Also, the FDA would not consider feeding performed according to a regulation as alternate 
feeding.  For example, due to the manner in which melengestrol acetate was approved (see 21 
CFR 558.342), feeding the entire approved daily amount of the drug melengestrol acetate in one 
feeding, but not in other feedings that day, would not be considered alternate feeding. 
 
 
Issued:  7/1/81 
Revised:  3/19 
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