U.S. Code of Federal Regulations
Regulations most recently checked for updates: Aug 28, 2025
(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.
(c) Related tolerances. See § 556.750 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 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 | Not for use in layers | 066104 | |
| (ii) 20 | Amprolium 72.6 to 113.5 | Broiler chickens: For prevention of necrotic enteritis caused by | For field conditions where only | 066104 |
| (iii) 20 | Amprolium 113.5 to 227 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | 066104 |
| (iv) 20 | Diclazuril, 0.91 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | 058198 |
| (v) 20 | Lasalocid 68 to 113 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | 066104 |
| (vi) 20 | Monensin 90 to 110 | Broiler chickens: For prevention of necrotic enteritis caused by | Feed continuously as the sole ration. Do not feed to laying chickens. See § 558.355(d) in this chapter. Monensin as provided by No. 058198 in § 510.600(c) of this chapter | 066104 |
| (vii) 20 | Narasin, 54 to 90 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | 066104 |
| (viii) 20 | Narasin, 27 to 54 plus nicarbazin, 27 to 54 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | 066104 |
| (ix) 20 | Salinomycin 40 to 60 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | |
| (x) 20 | Semduramicin 22.7 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | 066104 |
| (xi) 20 | Semduramicin (biomass) 22.7 | Broiler chickens: For prevention of necrotic enteritis caused by | 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 | 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) 13.5 to 16.0 | Monensin, 5 to 40 | Growing beef steers and heifers fed in confinement for slaughter: For improved feed efficiency and reduction of incidence of liver abscesses | Feed at every feeding to provide 50 to 480 mg monensin/head/day and 85 to 240 mg virginiamycin/head/day. No additional improvement in feed efficiency has been shown from feeding monensin at levels greater than 30 g/ton (360 mg monensin/head/day). A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal. See § 558.355(d) | 066104 |
| (iii) 13.5 to 16.0 | Monensin, 10 to 40 | Growing beef steers and heifers fed in confinement for slaughter: For the prevention and control of coccidiosis caused by | Feed at every feeding to provide 0.14 to 0.42 mg monensin/lb body weight per day, depending on the severity of coccidiosis challenge, up to a maximum of 480 mg monensin/head/day and 85 to 240 mg virginiamycin/head/day. A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal. See § 558.355(d) | 066104 |
| (iv) 13.5 to 16.0 | Monensin, 5 to 40; and lubabegron, 1.25 to 4.54 | Growing beef steers and heifers fed in confinement for slaughter during the last 14 to 91 days on feed: For reduction of ammonia gas emissions per pound of live weight and hot carcass weight, improved feed efficiency, and reduction of incidence of liver abscesses | Feed at every feeding as sole ration to provide 13 to 90 mg lubabegron/head/day, 50 to 480 mg monensin/head/day and 85 to 240 mg virginiamycin/head/day during the last 14 to 91 days on feed. No additional improvement in feed efficiency has been shown from feeding monensin at levels greater than 30 g/ton (360 mg monensin/head/day). A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal. See § 558.355(d) | 066104 |
| (v) 13.5 to 16.0 | Monensin, 10 to 40; and lubabegron, 1.25 to 4.54 | Growing beef steers and heifers fed in confinement for slaughter during the last 14 to 91 days on feed: For reduction of ammonia gas emissions per pound of live weight and hot carcass weight, the prevention and control of coccidiosis caused by | Feed at every feeding as sole ration to provide 13 to 90 mg lubabegron/head/day, 0.14 to 0.42 mg monensin/lb body weight per day, depending on the severity of coccidiosis challenge, up to a maximum of 480 mg monensin/head/day and 85 to 240 mg virginiamycin/head/day during the last 14 to 91 days on feed. A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal. See § 558.355(d) | 066104 |
| (vi) 13.5 to 16.0 | Monensin, 10 to 40; and ractopamine hydrochloride, 8.2 to 24.6 | Growing beef steers and heifers fed in confinement for slaughter during the last 28 to 42 days on feed: For increased rate of weight gain, improved feed efficiency, the prevention and control of coccidiosis caused by | Feed at every feeding as a sole ration to provide 70 to 430 mg ractopamine hydrochloride/head/day, 0.14 to 0.42 mg monensin/lb of body weight per day, depending upon severity of coccidiosis challenge, up to a maximum of 480 mg monensin/head/day and 85 to 240 mg virginiamycin/head/day during the last 28 to 42 days on feed. A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal. See § 558.355(d) | 066104 |
| (vii) 13.5 to 6.0 | Monensin, 10 to 40; and ractopamine hydrochloride, 9.8 to 24.6 | Growing beef steers and heifers fed in confinement for slaughter during the last 28 to 42 days on feed: For increased rate of weight gain, improved feed efficiency, increased carcass leanness, the prevention and control of coccidiosis caused by | Feed at every feeding as a sole ration to provide 90 to 430 mg ractopamine hydrochloride/head/day, 0.14 to 0.42 mg monensin/lb of body weight per day, depending upon severity of coccidiosis challenge, up to a maximum of 480 mg monensin/head/day and 85 to 240 mg virginiamycin/head/day during the last 28 to 42 days on feed. A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal. See § 558.355(d) | 066104 |
| (viii) 13.5 to 16.0 | Monensin, 10 to 40; and ractopamine hydrochloride, not to exceed 800 | Growing beef steers and heifers fed in confinement for slaughter during the last 28 to 42 days on feed: For increased rate of weight gain and improved feed efficiency, the prevention and control of coccidiosis caused by | Feed a minimum of 1.0 lb per head per day of this Type C top-dress medicated feed to provide 70 to 400 mg/head/day ractopamine hydrochloride during the last 28 to 42 days on feed. Must be top dressed onto or mixed at feeding with a Type C medicated feed containing 10 to 40 g/ton monensin and 13.5 to 16 g/ton virginiamycin (90% dry matter basis), to provide 0.14 to 0.42 mg monensin/lb of body weight per day, depending upon severity of coccidiosis challenge, up to a maximum of 480 mg monensin/head/day and 85 to 240 mg virginiamycin/head/day. See § 558.355(d) | 066104 |
