Animal & Veterinary

Steroid Hormone Implants Used for Growth in Food-Producing Animals

Since the 1950s, the Food and Drug Administration (FDA) has approved a number of steroid hormone drugs for use in beef cattle and sheep, including natural estrogen, progesterone, testosterone, and their synthetic versions. These drugs increase the animals’ growth rate, the efficiency by which they convert the feed they eat into meat, and the leanness of their meat. The FDA approves these drugs only after extensive studies have shown that the food from the treated animals is safe for people to eat, and that the drugs do not harm the treated animal or the environment. The drugs also have to work as intended.

These steroid hormone drugs are formulated as pellets that are placed under the skin on the back side of the animal’s ear. The pellets dissolve slowly under the skin and do not require removal. The ears of the treated animals are discarded at slaughter and not used for human food. Using scientific data, FDA establishes the acceptable safe limits for hormones in meat. A safe level for human consumption is a level of drug in the meat that would be expected to have no effect in humans based on extensive scientific study and review.

All approved implant products have a zero day withdrawal. This means that the meat from the animal is safe for humans to eat at any time after the animal is treated.

Naturally-Occurring Hormones

Some of the approved drugs are naturally produced throughout life in people and animals, such as estradiol (estrogen), progesterone, and testosterone. These natural hormones are necessary for normal development, growth, and reproduction. People are not at risk from eating food from animals treated with these drugs because the amount of additional hormone following drug treatment is very small compared with the amount of natural hormones that are normally found in the meat of untreated animals and that are naturally produced in the human body.

Synthetic Hormones

Some of the approved drugs are synthetic versions of the natural hormones, such as trenbolone acetate and zeranol. Just like the natural hormone implants, before FDA approved these drugs, FDA required extensive toxicological testing in animals to determine safe levels in the animal products that we eat (edible tissue). Furthermore, FDA required that the manufacturers demonstrate that the amount of hormone left in each edible tissue after treatment is below the appropriate safe level. As described above, a safe level is a level which would be expected to have no effect in humans.

No steroid hormones are approved for growth purposes in dairy cattle, veal calves, pigs, or poultry. All of the steroid hormone growth-promoting drugs are available for over-the-counter purchase in the U.S. and are generally given by the livestock producer at specific stages of the animals’ growth.

Additional Information

Information about approved hormonal implant products can be found in the Code of Federal Regulations (CFR), Title 21, Parts 522 and 556. Copies of the CFR may be found at your local public or university library and are for sale from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. In addition, the Code of Federal Regulations may be found on the Internet: http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=%2Findex.tpl.

Page Last Updated: 07/28/2014
Note: If you need help accessing information in different file formats, see Instructions for Downloading Viewers and Players.