Why Do They Do That? – Hormones

We recently had a Facebook post go viral! Well, not viral by standard definitions, but pretty good for us! At last count it was up to more than 17,000 engagements and more than 226,000 people reached. It was one of a regular series we post once a week hash-tagged #FridayFarmFact. It featured turkeys and as we were going into the Thanksgiving season it peaked a lot of interest. Here it is:

It could be that it went viral because it is such an interesting picture. Who doesn’t love seeing a bunch of turkeys just hanging out doing turkey stuff?

Or it could be that it went viral because there is still a lot of confusion about hormone use in production agriculture. Let’s assume it is the latter and let’s try to clear some things up. Do farmers use hormones when raising animals? And if so, why do they do that?

There are three things that often get lumped together in conversation but are actually very different and are often confused – hormones, antibiotics, and vaccines. We’ve discussed antibiotics and vaccines before. As a refresher, antibiotics are typically used to treat bacterial infections AFTER an animal like a pig or a human have gotten sick. Vaccines use a dead or modified virus to stimulate the body’s natural defenses against infection without causing the illness itself BEFORE getting sick. Hormones on the other hand are chemical messengers in the body. They are produced naturally in the endocrine gland and travel through the bloodstream. They control most major bodily functions – everything from hunger to reproduction to temperament. 

Hormones are produced naturally in all animals. Just like hormones regulate your bodily functions, they regulate bodily functions in animals such as livestock. So the meat, eggs, and milk that we get from livestock will have naturally occurring hormones in them. Any food label that reads “hormone-free” is simply not true. But some labels read “No Added Hormones.” For beef cattle and dairy cattle, farmers have found many positive benefits in including hormones in their management plan. Depending on the hormone, they can be given to the animals as a feed additive, a topical solution, or most commonly as an injected implant that releases the hormone slowly over time. The hormones – sometimes called steroids – are usually synthetic versions of naturally occurring hormones like estrogen, testosterone, and progesterone.

In beef cattle, the hormones help the animals grow more efficiently. This means they grow quicker using less feed. Not only is this cheaper for the farmer (they don’t spend as much on feed costs) but it can also be better for the environment. A recent study suggests that using hormones can reduce greenhouse gas emissions by ~5% by reducing the cattle’s environmental footprint. Dairy cattle may also be given bST or Bovine Somatotropin which is a growth hormone that increases milk production. The synthetic version of this naturally occurring hormone is called rbST. SciMoms does a great job of explaining that both the meat from beef cattle and the milk from dairy cattle is safe to consume even with these added hormones. 

Most people concerned about added hormones in food are concerned about human health consequences. Concerns often cite studies of children exhibiting signs of puberty at an earlier age. But in looking at the data, this trend began before the use of hormones in agriculture. So while there is a correlation, it doesn’t appear that early puberty is caused by hormones. Correlation does not equal causation. Because rbST is a protein hormone it is destroyed in human digestion and doesn’t make it into the human blood stream. Other concerns are over animal welfare issues where some dairy cows developed mastitis. But through improved genetics over the years, farmers have selected for cows that do not get mastitis as easily. The benefits of using hormones in beef and dairy cattle seem to far outweigh the risks.

As the #FridayFarmFact says, poultry (chickens, turkey, ducks, etc.) are raised without any added hormones. Regulations in the 1950s banned the use of added hormones in poultry. Chickens (and turkeys and ducks) are bigger today than they were 50 years ago because of genetics and breeding programs – not because of growth hormones. 


Increase in the size of broiler chickens from 1957-2005 due to breeding. Figure from Poult Sci. 2014;93(12):2970-2982. doi:10.3382/ps.2014-04291

Different breeds of chickens are selected for their  characteristics as good egg layers or good meat producers (broilers). Leghorns and Rhode Island Reds are usually raised for their eggs while Cornish Crosses and Delaware Broilers are usually raised for their meat. Some hormones have been tested on poultry but so far they don’t have a significant enough effect. They do have an effect on growth rate and food conversion efficiency so it is possible that we could see some changes in the law in the future. But for now, there are no added hormones in poultry. 

Neither are there added hormones in pork. Pigs have also gotten bigger, but that is because of better nutrition, good genetics programs, and good management programs – not from hormones. There could be some confusion because some hormones can be used in swine breeding programs to help manage estrous cycles, milk let down, and farrowing. But hormones cannot be used in pigs that will be harvested for meat. 

Hormones are not the simplest subject to understand because there are a lot of different hormones that all have different functions. Maybe the most important thing to understand is that beef cattle and dairy cattle production have federal regulations that allow for the use of hormones and poultry and pork production have different federal regulations that don’t allow for the use of hormones. In both instances though farmers are trying to find economically sound ways to improve their operations (while ensuring animals stay healthy) and federal regulators are trying to ensure that the food system stays safe. Based on what we know from research you can have confidence in the food that is being produced by farmers and that makes it to your table. Whether it is a whole turkey, a roast beef, or a big ham that sits on your holiday table this season, enjoy!

-Will

Other references:

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