---
kind: "section"
citation: "21 C.F.R. § 558.635"
title: "21"
number: "558.635"
heading: "Virginiamycin."
url: "https://uscodex.org/cfr/21/558.635"
---

# §558.635. Virginiamycin.

- (a) **Specifications.** Type A medicated articles containing 10, 20, 50, or 227 grams virginiamycin per pound.
- (b) **Sponsors.** See No. 066104 in [§ 510.600(c)](/cfr/21/510.600.md?p=c) of this chapter.
- (c) **Related tolerances.** See [§ 556.750](/cfr/21/556.750.md) of this chapter.
- (d) **Special considerations.**
  - (1) Federal law restricts medicated feed containing this veterinary feed directive (VFD) drug to use by or on the order of a licensed veterinarian. See [§ 558.6](/cfr/21/558.6.md) for additional requirements.
  - (2) The expiration date of VFDs for virginiamycin medicated feeds must not exceed 6 months from the date of issuance. VFDs for virginiamycin shall not be refilled.
  - (3) **Not for use in breeding swine over 120 pounds.**
  - (4) Dilute Type A article with at least 10 pounds of a feed ingredient prior to final mixing in 1 ton of Type C feed.
- (e) **Conditions of use—**
  - (1) **Chickens—**
  - (2) **Swine—**
  - (3) **Cattle—**

## Notes

### Amendments

[81 FR 95022, Dec. 27, 2016, as amended at 82 FR 11512, Feb. 24, 2017; 82 FR 21692, May 10, 2017; 85 FR 18125, Apr. 1, 2020; 87 FR 10972, Feb. 28, 2022; 88 FR 14908, Mar. 10, 2023; 90 FR 40972, Aug. 22, 2025]

### Authority

Authority: 21 U.S.C. 354, 360b, 360ccc, 360ccc-1, 371.

### Source

Source: 40 FR 13959, Mar. 27, 1975, unless otherwise noted.

### Amendments

[81 FR 95022, Dec. 27, 2016, as amended at 82 FR 11512, Feb. 24, 2017; 82 FR 21692, May 10, 2017; 85 FR 18125, Apr. 1, 2020; 87 FR 10972, Feb. 28, 2022; 88 FR 14908, Mar. 10, 2023; 90 FR 40972, Aug. 22, 2025]