#### § 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) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)).

(c) *Related tolerances.* See [§ 556.750 of this chapter](/on/2024-09-17/title-21/section-556.750).

(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](/on/2024-09-17/title-21/section-558.6) 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* —

| Virginiamycin grams/ton | Combination in grams/ton | Indications for use | Limitations | Sponsors |
| --- | --- | --- | --- | --- |
| (i) 20 | | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin | Not for use in layers | 066104 |
| (ii) 20 | Amprolium 72.6 to 113.5 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and for the prevention of coccidiosis caused by *Eimeria tenella* | For field conditions where only *E. tenella* is the major problem, feed continuously as the sole ration. Use as the sole source of amprolium. Do not use in feeds containing bentonite. Not for use in laying chickens. Amprolium as provided by No. 016592 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |
| (iii) 20 | Amprolium 113.5 to 227 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and for the prevention of coccidiosis where immunity to coccidiosis is not desired | For most field conditions as they exist under modern management practices, feed 113.5 g/ton amprolium continuously. Where severe coccidiosis conditions exist, feed 227 g/ton. Use as the sole source of amprolium. Do not use in feeds containing bentonite. Not for use in laying chickens. Amprolium as provided by No. 016592 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |
| (iv) 20 | Diclazuril, 0.91 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and for the prevention of coccidiosis caused by *Eimeria tenella, E. necatrix, E. acervulina, E. brunetti, E. mitis* (*mivati),* and *E. maxima.* Because diclazuril is effective against *E. maxima* later in its life cycle, subclinical intestinal lesions may be present for a short time after infection. Diclazuril was shown in studies to reduce lesions scores and improve performance and health of birds challenged with *E. maxima* | Feed continuously as the sole ration. Do not feed to birds producing eggs for human consumption. Diclazuril as provided by No. 058198 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 058198 |
| (v) 20 | Lasalocid 68 to 113 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and for the prevention of coccidiosis caused by *Eimeria tenella, E. necatrix,* *E. acervulina, E. brunetti,* *E. mivati,* and *E. maxima* | Feed continuously as the sole ration. Do not feed to laying chickens. For broiler or fryer chickens only. Lasalocid as provided by No. 054771 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |
| (vi) 20 | Monensin 90 to 110 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and as an aid in the prevention of coccidiosis caused by *Eimeria necatrix, E. tenella,* *E. acervulina, E. brunetti,* *E. maxima,* and *E. mivati* | Feed continuously as the sole ration. Do not feed to laying chickens. See [§ 558.355(d)](/on/2024-09-17/title-21/section-558.355#p-558.355(d)) in this chapter. Monensin as provided by No. 058198 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |
| (vii) 20 | Narasin, 54 to 90 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin and for the prevention of coccidiosis caused by *Eimeria necatrix, E. tenella, E. acervulina, E. brunetti, E. mivati,* and *E. maxima* | Feed as the sole ration for broiler chickens. Do not feed to chickens producing eggs for human consumption. Do not allow adult turkeys, horses, or other equines access to narasin formulations. Ingestion of narasin by these species has been fatal. Naracin as provided by No. 066104 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |
| (viii) 20 | Narasin, 27 to 54 plus nicarbazin, 27 to 54 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin and for the prevention of coccidiosis caused by *Eimeria necatrix, E. tenella, E. acervulina, E. brunetti, E. mivati,* and *E. maxima* | Feed as the sole ration for broiler chickens. Do not feed to chickens producing eggs for human consumption. Nicarbazin medicated broilers may show reduced heat tolerance if exposed to high temperature and high humidity. Provide adequate drinking water and ventilation during these periods. Do not allow adult turkeys, horses, or other equines access to narasin formulations. Ingestion of narasin by these species has been fatal. Naracin as provided by No. 066104 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |
| (ix) 20 | Salinomycin 40 to 60 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and for the prevention of coccidiosis caused by *Eimeria tenella, E. necatrix,* *E. acervulina, E. maxima, E. brunetti,* and *E. mivati* | Feed continuously as the sole ration. Do not feed to chickens over 16 weeks of age. Do not feed to laying chickens. Not approved for use with pellet binders. May be fatal if accidentally fed to adult turkeys or horses. Salinomycin as provided by No. 016592 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | |
| (x) 20 | Semduramicin 22.7 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and for the prevention of coccidiosis caused by *Eimeria acervulina, E. brunetti,* *E. maxima, E mivati/mitis,* *E. necatrix,* and *E. tenella* | Feed continuously as the sole ration. Do not feed to laying hens. Semduramicin as provided by No. 066104 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |
| (xi) 20 | Semduramicin (biomass) 22.7 | Broiler chickens: For prevention of necrotic enteritis caused by *Clostridium perfringens* susceptible to virginiamycin; and for the prevention of coccidiosis caused by *Eimeria acervulina, E. brunetti,* *E. maxima, E mivati/mitis,* *E. necatrix,* and *E. tenella* | Feed continuously as the sole ration. Withdraw 1 day before slaughter. Do not feed to laying hens. Semduramicin as provided by No. 066104 in [§ 510.600(c) of this chapter](/on/2024-09-17/title-21/section-510.600#p-510.600(c)) | 066104 |

(2) *Swine* —

| Virginiamycin grams/ton | Combination in grams/ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- | --- |
| (i) 25 | | Growing-finishing swine: As an aid in control of dysentery in swine up to 120 pounds in animals or on premises with a history of swine dysentery but where symptoms have not yet occurred | | 066104 |
| (ii) 50 or 100 | | Growing-finishing swine: For treatment and control of swine dysentery in swine up to 120 pounds | Feed 100 grams per ton for 2 weeks, 50 grams per ton thereafter | 066104 |
| (iii) 100 | | Growing-finishing swine: For treatment of swine dysentery in nonbreeding swine over 120 pounds | Feed for 2 weeks | 066104 |

(3) *Cattle* —

| Virginiamycin grams/ton | Combination in grams/ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- | --- |
| (i) 13.5 to 16.0 | | Cattle fed in confinement for slaughter: For reduction of incidence of liver abscesses | Feed continuously as the sole ration to provide 85 to 240 milligrams per head per day. Not for use in animals intended for breeding | 066104 |
| (ii) [Reserved] | | | | |

[[81 FR 95022](https://www.federalregister.gov/citation/81-FR-95022), Dec. 27, 2016, as amended at [82 FR 11512](https://www.federalregister.gov/citation/82-FR-11512), Feb. 24, 2017; [82 FR 21692](https://www.federalregister.gov/citation/82-FR-21692), May 10, 2017; [85 FR 18125](https://www.federalregister.gov/citation/85-FR-18125), Apr. 1, 2020; [87 FR 10972](https://www.federalregister.gov/citation/87-FR-10972), Feb. 28, 2022; [88 FR 14908](https://www.federalregister.gov/citation/88-FR-14908), Mar. 10, 2023]