#### § 558.665 Zilpaterol.

(a) *Specifications.* Type A medicated articles containing 21.77 grams (g) zilpaterol hydrochloride per pound.

(b) *Approvals.* See No. 000061 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)).

(c) *Tolerances.* See [§ 556.765 of this chapter](/on/2024-09-23/title-21/section-556.765).

(d) *Special considerations.*

(1) Labeling shall bear the following caution statements: “Zilpaterol hydrochloride is not for use in animals intended for breeding. Do not allow horses or other equines access to feed containing zilpaterol. Do not use in veal calves.”

(2) Labeling of Type A medicated articles and Type B medicated feeds used to manufacture complete Type C medicated feeds shall bear the caution statement in [paragraph (d)(3)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)(3)) of this section.

(3) Labeling of complete Type C medicated feeds shall bear the following caution statements: “Not to be fed to cattle in excess of 90 mg zilpaterol/head/day in complete feed. If pen consumption of complete feed exceeds 26.5 lb/head/day (90 percent dry matter basis), zilpaterol should not be fed in complete feed.”

(4) Type B Liquid Feeds can be manufactured containing 68 to 680 g zilpaterol hydrochloride/ton. The liquid Type B feeds must be maintained at a pH of 3.8 to 7.5. For liquid feeds stored in recirculating tank systems: Recirculate immediately prior to use for not less than 10 minutes, moving not less than 1 percent of the tank contents per minute from the bottom of the tank to the top. Recirculate daily as described even when not used. For liquid feeds stored in mechanical, air or other agitation-type tank systems: Agitate immediately prior to use for not less than 10 minutes, creating a turbulence at the bottom of the tank that is visible at the top. Agitate daily as described even when not used.

(e) *Conditions of use in cattle.* It is administered in feed as follows:

| Zilpaterol hydrochloride in grams/ton | Combination in grams/ton | Indications for use | Limitations | Sponsor |
| --- | --- | --- | --- | --- |
| (1) 6.8 | | Cattle fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed | Feed continuously as the sole ration during the last 20 to 40 days on feed to provide 60 to 90 mg zilpaterol hydrochloride per head per day. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section | 000061 |
| (2) 6.8 | Monensin 10 to 40 | Cattle fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed; for prevention and control of coccidiosis due to *Eimeria bovis* and *E. zuernii* | Feed continuously as the sole ration during the last 20 to 40 days on feed to provide 60 to 90 mg zilpaterol hydrochloride per head per day and 0.14 to 0.42 mg monensin per pound of body weight per day depending on the severity of the coccidiosis challenge, up to 480 mg/head/day monensin. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section. See paragraph [§ 558.355(d) of this chapter](/on/2024-09-23/title-21/section-558.355#p-558.355(d)) Monensin as provided by No. 058198 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)) | 000061 058198 |
| (3) 6.8 | Melengestrol acetate to provide 0.25 to 0.5 mg/head/day | Heifers fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed; and for suppression of estrus (heat) | Feed continuously as the sole ration during the last 20 to 40 days on feed to provide 60 to 90 mg zilpaterol hydrochloride per head per day. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section Melengestrol acetate as provided by Nos. 058198 or 054771 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)) | 000061 058198 |
| (4) 6.8 | Monensin 10 to 40 plus melengestrol acetate to provide 0.25 to 0.5 mg/head/day | Heifers fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed; for prevention and control of coccidiosis due to *Eimeria bovis* and *E. zuernii;* and for suppression of estrus (heat) | Feed continuously as the sole ration during the last 20 to 40 days on feed to provide 60 to 90 mg zilpaterol hydrochloride per head per day and 0.14 to 0.42 mg monensin per pound of body weight per day depending on the severity of the coccidiosis challenge, up to 480 mg/head/day monensin. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section. See paragraphs [§§ 558.342(d)](/on/2024-09-23/title-21/section-558.342#p-558.342(d)) and [558.355(d) of this chapter](/on/2024-09-23/title-21/section-558.355#p-558.355(d)) Monensin as provided by No. 058198; melengestrol acetate as provided by Nos. 058198 or 054771 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)) | 000061 058198 |
| (5)-(6) [Reserved] | | | | |
| (7) 6.8 to 24 | | Cattle fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed | Feed continuously during the last 20 to 40 days on feed to provide 60 mg zilpaterol hydrochloride per head per day. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section | 000061 |
| (8) 6.8 to 24 | Monensin 10 to 40 | Cattle fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed; and for prevention and control of coccidiosis due to *Eimeria bovis* and *E. zuernii* | Feed continuously during the last 20 to 40 days on feed to provide 60 mg zilpaterol hydrochloride per head per day and 0.14 to 0.42 mg monensin per pound of body weight per day depending on the severity of the coccidiosis challenge, up to 480 mg/head/day monensin. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section. See paragraph [§ 558.355(d) of this chapter](/on/2024-09-23/title-21/section-558.355#p-558.355(d)) Monensin as provided by No. 058198 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)) | 000061 |
| (9) 6.8 to 24 | Melengestrol acetate to provide 0.25 to 0.5 mg/head/day | Heifers fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed; and for suppression of estrus (heat) | Feed continuously during the last 20 to 40 days on feed to provide 60 mg zilpaterol hydrochloride per head per day. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section. See paragraph [§ 558.342(d) of this part](/on/2024-09-23/title-21/part-558/section-558.342#p-558.342(d)) Melengestrol acetate as provided by No. 054771 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)) | 000061 |
| (10) 6.8 to 24 | Monensin 10 to 40, plus melengestrol acetate to provide 0.25 to 0.5 mg/head/day | Heifers fed in confinement for slaughter: For increased rate of weight gain, improved feed efficiency, and increased carcass leanness in cattle fed in confinement for slaughter during the last 20 to 40 days on feed; for prevention and control of coccidiosis due to *Eimeria bovis* and *E. zuernii;* and for suppression of estrus (heat) | Feed continuously during the last 20 to 40 days on feed to provide 60 mg zilpaterol hydrochloride per head per day and 0.14 to 0.42 mg monensin per pound of body weight per day depending on the severity of the coccidiosis challenge, up to 480 mg/head/day monensin. Withdrawal period: 3 days. See [paragraph (d)](/on/2024-09-23/title-21/section-558.665#p-558.665(d)) of this section. See paragraphs [§§ 558.342(d)](/on/2024-09-23/title-21/section-558.342#p-558.342(d)) and [558.355(d) of this chapter](/on/2024-09-23/title-21/section-558.355#p-558.355(d)) Monensin as provided by No. 058198; melengestrol acetate as provided by No. 054771 in [§ 510.600(c) of this chapter](/on/2024-09-23/title-21/section-510.600#p-510.600(c)) | 000061 |

(f) Zilpaterol may also be used in combination with tylosin as in [§ 558.625](/on/2024-09-23/title-21/section-558.625).

[[71 FR 53006](https://www.federalregister.gov/citation/71-FR-53006), Sept. 8, 2006, as amended at [72 FR 9245](https://www.federalregister.gov/citation/72-FR-9245), Mar. 1, 2007; [72 FR 6019](https://www.federalregister.gov/citation/72-FR-6019), Feb. 1, 2008; [73 FR 14385](https://www.federalregister.gov/citation/73-FR-14385), Mar. 18, 2008; [73 FR 16755](https://www.federalregister.gov/citation/73-FR-16755), Mar. 31, 2008; [73 FR 18959](https://www.federalregister.gov/citation/73-FR-18959), Apr. 8, 2008; [73 FR 19432](https://www.federalregister.gov/citation/73-FR-19432), Apr. 10, 2008; [74 FR 61517](https://www.federalregister.gov/citation/74-FR-61517), Nov. 25, 2009; [75 FR 11451](https://www.federalregister.gov/citation/75-FR-11451), Mar. 11, 2010; [77 FR 31724](https://www.federalregister.gov/citation/77-FR-31724), May 30, 2012; [78 FR 42008](https://www.federalregister.gov/citation/78-FR-42008), July 15, 2013; [78 FR 52852](https://www.federalregister.gov/citation/78-FR-52852), Aug. 27, 2013; [80 FR 13232](https://www.federalregister.gov/citation/80-FR-13232), Mar. 13, 2015; [80 FR 53460](https://www.federalregister.gov/citation/80-FR-53460), Sept. 4, 2015; [81 FR 48703](https://www.federalregister.gov/citation/81-FR-48703), July 26, 2016; [81 FR 95025](https://www.federalregister.gov/citation/81-FR-95025), Dec. 27, 2016]