Learning to Love rbST

In the United States, June marked national dairy month. And this one was special: 2023 marks 30 years since the U.S. Food and Drug Administration (FDA) approved recombinant Bovine Somatotropin hormone (rbST).

rbST is a synthetic hormone based on the somatotropin hormone that cattle naturally produce. Both the natural and synthetic versions play a role in how nutrients in the animal's diet are directed toward body functions (for example, they reduce how much dietary nutrients are needed for maintenance needs like respiration making more available for milk production). As such, rbST makes milk production more efficient, reducing the amount of energy, protein, and feed needed to produce a unit of milk by 11.8%, 7.5%, and 8.1%, respectively.

Yet, most milk cartons proudly claim they're rbST-free.

As dairy companies and cooperatives—including Danone, Dairy Farmers of America, and Nestle—set carbon neutrality goals, it’s counterproductive for them to leave carbon-reduction technologies like rbST on the sidelines. All of these companies, and more, market rbST-free milk in essence disavowing its use.

Despite the proven safety of rbST and its effectiveness in reducing the carbon and nitrogen footprint of dairy cows, the industry eliminated rbST use because of consumer pressure. Consumers Union, the public policy arm of Consumer Reports, led consumers to believe that rbST use creates antibiotic resistance, increases growth hormone levels in milk, and leads to spread of mad cow disease.

To be clear: Both the natural and synthetic versions of somatotropin have no biological activity once metabolized in the animal—allowing for milk to immediately enter the supply chain with no threat of the hormone impacting humans. Specifically, somatotropin must be injected to be biologically active. There’s also no evidence that the hormone is linked with the spread of mad cow disease; although some activists groups tried to assert that the increased dietary protein intake cows would need to meet the increased milk production would result in more animal by-products being fed to cattle, thus increasing the incidences of mad cow disease. This is no longer a concern—because it is illegal to feed mammalian by-products to cattle.

What consumers were not told was that using rbST reduces the number of cows and arable land needed to meet milk demand. A researcher modeled the environmental impacts of treating ~15% of the U.S. dairy herd (one million milking cows in 2006) with rbST. The results showed that baseline milk yield could be met with 157,103 fewer cows. Imagine the implications of even greater adoption. Fewer cows equates to less enteric methane—a potent, but short-lived greenhouse gas—and less manure. The researcher’s model also showed that using rbST on 1 million cows reduced methane emissions by 41 million kg per year and could free up as much as 219,000 hectares of cropland previously used for feed for other uses like reforestation.

The case is clear, as one Pennsylvania dairy farmer put it to me: “If you can milk less cows and get the same production—why the hell wouldn’t you?”

Still, there’s concern that rbST adoption could lead to a vicious cycle where farmers don’t decrease their herds, dairy prices fall, demand rises, and production increases—negating the emissions reductions. But such concerns seem misplaced given the pricing controls of the Federal Milk Marketing Orders and milk contracts of buyers like Dairy Farmers of America (DFA). In other words, no dairy farmer has reason to go over their contracted amount by milking more cows. If they did, they know they’d face consequences.

The FDA first approved a bST product in 1993. Thirty years since inception—it’s time to revive the value of this scientific innovation in increasing revenues, reducing methane emissions, and reducing cropland use in dairy production. An analysis of New York dairy farms showed, it made economic sense to adopt rbST especially when coupled with adjusting herd size, but rbST also makes environmental sense. Planetary warming is one of the most pressing issues of the 21st century and the science of the 20th century has a solution.