cattle and sheep
Diet & Nutrition

Growth Hormones in Food Animals: What’s the Risk?

Growth hormones are routinely given to cows and sheep being produced for their meat, and are injected into dairy cows. These hormones make their way to our dinner tables, and also contaminate the environment via manure and runoff from feedlots into local streams. Studies have shown that these factors can constitute risks to our health.

Why Are Hormones Given to Food Animals?

Since 1950 the US Food and Drug Administration (FDA) has allowed the use of steroid hormones in cows and sheep being produced for meat. These hormones promote growth and improve feed efficiency, key mineral absorption, and meat quality. Non-steroidal hormones such as rBGH (recombinant bovine growth hormone) are also injected into dairy cows to increase their milk production.

The hormones given to cattle and sheep are either provided via pellets injected into the animals or are mixed into the feed. If pellets are used, they are removed prior to slaughter to prevent unused hormones from finding their way into our meat.

Using the hormones translates to cost savings for the farmer and consumers. For beef, animals experience an 8-25% weight gain and a 10-15% gain in feed efficiency resulting in cost savings of $30 to $80 per cow. The meat that shows up at the grocery store should cost less for consumers, and the meat should be of better quality with an increased lean/fat ratio.

Poultry are not given hormones. So that chicken package you pay a bit more for because it says it is “hormone-free” is simply a marketing ploy. All chickens are produced hormone-free, although they may be given antibiotics, a variety of drugs, and genetically modified feed.

Poultry producers have no desire to use hormones in poultry as it is not cost effective and would require farmers to physically inject tens of thousands of birds several times a day. Poultry is fattened by feed which is typically genetically modified.


Other drugs and antibiotics are also routinely given to poultry, pigs, and cattle to promote better growth with less feed. Ractopamine is one example that is used in pigs. It is not a hormone, but is a drug that promotes growth. Many countries have banned its use.

Growth hormones are not used in “aquaculture” (fish farms) as they are prohibited by the FDA. Additionally hormones have not been shown to improve efficiency, growth or cost savings in farmed fish.

What you need to know about hormones given to cattle and sheep

Three natural steroid hormones and three synthetic hormones are used today in the US by beef cattle producers. The three synthetic hormones are trenbolone, melengestrol, and zeranol. The three steroid hormones are estradiol, testosterone and progesterone.

These hormones are also found naturally in people and all mammals. They are the primary reproductive hormones that play a role in sexual organ development, the onset of puberty, sexual maturation, and sexual behavior.