[Code of Federal Regulations] [Title 21, Volume 6] [Revised as of January 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 21CFR522.840] [Page 237] TITLE 21--FOOD AND DRUGS CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) PART 522--IMPLANTATION OR INJECTABLE DOSAGE FORM NEW ANIMAL DRUGS--Table of Contents Sec. 522.840 Estradiol. (a) Specifications. Each silicone rubber implant contains 25.7 or 43.9 milligrams of estradiol. (b) Sponsor. See No. 021641 in Sec. 510.600(c) of this chapter. (c) Conditions of use. It is used for implantation in steers and heifers as follows: (1) Amount. Insert one 25.7-milligram implant every 200 days; insert one 43.9-milligram implant every 400 days. (2) Indications for use. For increased rate of weight gain in suckling and pastured growing steers; for improved feed efficiency and increased rate of weight gain in confined steers and heifers. (3) Limitations. For subcutaneous ear implantation in steers and heifers only. A second implant may be used if desired. No additional effectiveness may be expected from reimplanting in less than 200 days for the 25.7-milligram implant or 400 days for the 43.9 milligram implant. Increased sexual activity (bulling, riding, and excitability) has been reported in implanted animals. [51 FR 22276, June 19, 1986, as amended at 57 FR 41861, Sept. 14, 1992; 66 FR 56035, Nov. 6, 2001]