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21 CFR § 558.55 - Amprolium. 

---
identifier: "/us/cfr/t21/s558.55"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "21 CFR § 558.55 - Amprolium."
title_number: 21
title_name: "Food and Drugs"
section_number: "558.55"
section_name: "Amprolium."
chapter_name: "FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "E"
subchapter_name: "ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS"
part_number: "558"
part_name: "NEW ANIMAL DRUGS FOR USE IN ANIMAL FEEDS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "21 U.S.C. 354, 360b, 360ccc, 360ccc-1, 371."
regulatory_source: "40 FR 13959, Mar. 27, 1975, unless otherwise noted."
cfr_part: "558"
---

# 558.55 Amprolium.

(a) *Specifications.* Type A medicated article containing 25 percent amprolium.

(b) *Sponsor.* No. 016592 in § 510.600(c) of this chapter.

(c) *Related tolerances.* See § 556.50 of this chapter.

(d) *Special considerations.* Do not use in Type B or Type C medicated feeds containing bentonite.

(e) *Conditions of use*—(1) *Cattle.* It is used as follows:

| Amprolium in grams per ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- |
| (i) 113.5 to 11, 350; to provide 5 milligrams per kilogram of body weight per day | Calves: As an aid in the prevention of coccidiosis caused by  and | Top-dress on or mix in the daily ration. Feed for 21 days when experience indicates that coccidiosis is likely to be a hazard, as the sole source of amprolium. Withdraw 24 hours before slaughter. A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal | 016592 |
| (ii) 113.5 to 11, 350; to provide 10 milligrams per kilogram of body weight per day | Calves: As an aid in the treatment of coccidiosis caused by  and | Top-dress on or mix in the daily ration. Feed for 5 days as the sole source of amprolium. Withdraw 24 hours before slaughter. A withdrawal period has not been established for this product in preruminating calves. Do not use in calves to be processed for veal | 016592 |

(2) *Chickens.* It is used as follows:

| Amprolium in grams per ton | Combination in grams per ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- | --- |
| (i) 36.3 to 113.5 |  | Replacement chickens: For development of active immunity to coccidiosis | Feed continuously until onset of production as follows: | 016592 |

| Growing conditions | Up to 5 weeks of age | From 5 to 8 weeks of age | Over 8 weeks of age |
| --- | --- | --- | --- |
| Severe exposure to coccidiosis | 113.5 | 72.6-113.5 | 36.3-113.5 |
|  | (0.0125%) | (0.008%-0.0125%) | (0.004%-0.0125%) |
| Moderate exposure to coccidiosis | 72.6-113.5 | 54.5-113.5 | 36.3-113.5 |
|  | (0.008%-0.0125%) | (0.006%-0.0125%) | (0.004%-0.0125%) |
| Slight exposure to coccidiosis | 36.3-113.5 | 36.3-113.5 | 36.3-113.5 |
|  | (0.004%-0.0125%) | (0.004%-0.0125%) | (0.004%-0.0125%) |

| Amprolium in grams per ton | Combination in grams per ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- | --- |
| (ii) 36.3 to 113.5 | Bacitracin methylenedisalicylate 4 to 50 | Replacement chickens: For development of active immunity to coccidiosis; and for increased rate of weight gain and improved feed efficiency | Feed according to subtable in item (i). Bacitracin methylenedisalicylate as provided by No. 054771 in § 510.600(c) of this chapter | 054771 |
| (iii) 72.6 to 113.5 |  | Broiler chickens: For prevention of coccidiosis caused by  only | Feed continuously as the sole ration; as sole source of amprolium | 016592 |
| (iv) 72.6 to 113.5 | Bambermycins 1 to 2 | Broiler chickens: For prevention of coccidiosis caused by  only; and for increased rate of weight gain and improved feed efficiency | Feed continuously as the sole ration; as sole source of amprolium. Bambermycins as provided by No. 016592 in § 510.600(c) of this chapter | 016592 |
| (v) 113.5 |  | 1. Laying chickens: For prevention of coccidiosis | Feed continuously as the sole ration; as the sole source of amprolium | 016592 |
|  |  | 2. Laying chickens: For treatment of coccidiosis in moderate outbreaks | Feed for 2 weeks |  |
| (vi) 113.5 to 227 |  | 1. Replacement chickens: For prevention of coccidiosis where immunity to coccidiosis is not desired | Feed continuously from day-old until onset of production; as the sole source of amprolium | 016592 |
|  |  | 2. Broiler chickens: For prevention of coccidiosis where immunity to coccidiosis is not desired | Feed continuously as the sole ration; as sole source of amprolium |  |
| (vii) 113.5 to 227 | Bambermycins 1 to 2 | Broiler chickens: For prevention of coccidiosis where immunity to coccidiosis is not desired; and for increased rate of weight gain and improved feed efficiency | Feed continuously as the sole ration; as sole source of amprolium. Bambermycins as provided by No. 016592 in § 510.600(c) of this chapter | 016592 |
| (viii) 227 |  | Laying chickens: For treatment of coccidiosis in severe outbreaks. | Feed for 2 weeks | 016592 |

(3) *Turkeys.* It is used as follows:

| Amprolium in grams per ton | Combination in grams per ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- | --- |
| (i) 113.5 | Bambermycins 1 to 4 | Growing turkeys: For prevention of coccidiosis; and for increased rate of weight gain and improved feed efficiency | Feed continuously as the sole source of amprolium; bambermycins as provided by No. 016592 in § 510.600(c) of this chapter | 016592 |
| (ii) 113.5 to 227 |  | Turkeys: For prevention of coccidiosis | Feed continuously as the sole ration; as sole source of amprolium | 016592 |

(4) *Pheasants.* It is used as follows:

| Amprolium in grams per ton | Combination in grams per ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- | --- |
| (i) 159 |  | Growing pheasants: For the prevention of coccidiosis caused by  and | Feed continuously as sole ration. Use as sole source of amprolium | 016592 |
| (ii) [Reserved] |  |  |  |  |

(5) *Permitted combinations.* Amprolium may also be used in combination with:

(i) Virginiamycin as in § 558.635.

(ii) [Reserved]

[41 FR 10985, Mar. 15, 1976]

For  citations affecting § 558.55, see the List of CFR Sections Affected, which appears in the Finding Aids section of the printed volume and at