New Animal Drugs for Use in Animal Feeds
The FDA regulation governing new animal drugs used in animal feeds — the interface the medicated-feed CGMP rules (Parts 225/226) assume. It houses the Veterinary Feed Directive framework (§558.6), under which medically important antimicrobials in feed may be used only under a veterinarian's written VFD order, plus the conditions of approval for each drug permitted in feed, listed drug by drug.
What this does not cover
stated in the document's own scope- Governs the use of new animal drugs in feeds; the manufacturing controls for the feeds themselves are Parts 225/226, and feed-mill licensing is Part 515.
- The VFD framework covers drugs designated as VFD drugs — centrally, medically important antimicrobials in feed; it is not a general prescription regime for all feed additives.
- A US regulation: EU medicated feed runs under Regulations (EU) 2019/4 and 2019/6, a separate system with its own prescription rules.
Always verify against the current published text before relying on it for a submission or inspection.
Overview
21 CFR Part 558, "New Animal Drugs for Use in Animal Feeds", governs the drug side of medicated feed: which new animal drugs may be used in feeds, under what codified conditions, and — through §558.6 — the Veterinary Feed Directive framework that places medically important antimicrobials in feed under veterinary oversight. A VFD drug may be used only pursuant to a written directive from a licensed veterinarian operating within a veterinarian-client-patient relationship; the veterinarian, the distributor, and the client each keep the order for two years, and distributors file notifications and acknowledgments that let FDA trace the chain. The bulk of the part is the drug-by-drug listing of approved conditions of use — species, indications, use levels, and limitations — that a feed formulation must match.
Scope & applicability
Feed mills, distributors, veterinarians, and animal producers using new animal drugs in feed for the US market. Manufacturing controls for the feeds themselves are in Parts 225 (medicated feeds) and 226 (Type A medicated articles); licensing of feed mills sits in Part 515.
Legal basis & how it acquires force
A regulation under the new-animal-drug provisions of the FD&C Act (section 512 and, for VFD drugs, section 504). The Veterinary Feed Directive final rule of 2015 rebuilt §558.6, and from January 2017 medically important antimicrobials in feed transitioned from over-the-counter to VFD status under FDA's judicious-use policy (Guidance for Industry #213). A feed bearing a new animal drug outside its codified conditions, or a VFD drug used without a lawful directive, renders the feed adulterated.
Document structure
| Part | Covers |
|---|---|
| Subpart A — General provisions | Definitions, medicated-feed applications, and the requirement to use drugs per their codified conditions |
| §558.6 — Veterinary Feed Directive drugs | The VFD order requirements, the veterinarian-client-patient relationship, record retention, and distributor notification and acknowledgment duties |
| Subpart B — Specific new animal drugs approved for use in feed | The drug-by-drug conditions of approval: species, indications, use levels, combinations, and limitations |
| Interfaces with Parts 225, 226, and 515 | Manufacturing CGMP for medicated feeds and Type A articles, and medicated feed mill licensing |
Key requirements
- Use of VFD drugs in feed only under a lawful Veterinary Feed Directive issued by a licensed veterinarian (§558.6)
- VFD orders within the veterinarian-client-patient relationship, with copies retained by veterinarian, distributor, and client for two years
- Distributor notification and acknowledgment duties for VFD feeds
- Use of each drug only per its codified conditions of approval (species, indication, level, limitations)
Implementation tips
- Treat VFD records as GxP records: the two-year retention, order completeness, and distributor acknowledgment chain are what FDA reviews at feed-mill and distributor inspections
Revision notes
The Veterinary Feed Directive final rule of 2015 rebuilt §558.6; from January 2017, medically important antimicrobials used in feed transitioned from over-the-counter to VFD status under FDA's judicious-use initiative.
Where this control fails
live FDA enforcementLive FDA recalls SPEQ maps to this standard’s topics — a SPEQ interpretation, not an FDA classification.
International alignment
Part 558 is the regulatory hinge between animal-drug law and feed manufacturing: Parts 225 and 226 supply the CGMP for medicated feeds and Type A medicated articles, Part 515 licenses feed mills, and Part 558 dictates which drugs those systems may run and under whose authority. Internationally, the EU reached a parallel position through Regulation (EU) 2019/6 and the medicated-feed regulation (EU) 2019/4, which likewise subject antimicrobial feed medication to veterinary prescription.
21 CFR Part 558: frequently asked questions
Quick answers to common questions about 21 CFR Part 558.
What is a Veterinary Feed Directive?
A written order from a licensed veterinarian, issued within a veterinarian-client-patient relationship, authorising the use of a VFD drug in animal feed under the conditions of its approval. The client, the veterinarian, and the feed distributor each retain the order for two years, and the feed may only be manufactured and fed per the directive.
Why did antimicrobials in feed move to VFD status?
Under FDA's judicious-use initiative, medically important antimicrobials lost over-the-counter status in feed from January 2017: production uses (growth promotion) were withdrawn, and remaining therapeutic uses came under veterinary oversight through the VFD framework of §558.6.
How does Part 558 relate to Parts 225 and 226?
Part 558 says which drugs may go into feed and on whose authority; Part 225 sets the CGMP for manufacturing the medicated feeds; Part 226 sets the CGMP for the concentrated Type A medicated articles the mills dilute. A compliant medicated-feed operation needs all three, plus a Part 515 mill licence where required.
This standard in practice
Recall domain is a SPEQ mapping of this standard’s topics, not an FDA classification.