Bovine Growth Hormone (BGH) is a naturally occurring hormone secreted by the pituitary glands of cattle. You may also hear BGH referred to as “Bovine Somatotropin,” or BST. This hormone enters the bloodstream and regulates the rate of growth and milk production for the cow. As early as the 1930s, people noted that when BGH levels were increased in cattle by harvesting the hormone from cow cadavers, milk production increased as well, and several firms because interested in using BGH to boost milk production.
In the 1980s, the Monsanto Company figured out how to produce BGH synthetically, by genetically altering bacteria so that they would produce the hormone. This process is known as “recombinant DNA,” reflecting the idea that the DNA of the host bacteria has been altered for a specific end purpose. The result was rBGH, a synthetic form of BGH which was easy to produce on a large scale, and it was approved for use in the United States in the early 1990s.
Cows treated with rBGH do indeed produce more milk, sometimes as much as 25% more, but the hormone is very hard on their bodies. Increased BGH levels lead to calcium deficiency in the bone and a variety of other health problems. Because BGH can be used to force cows to produce milk year-round, whether or not they calve, the hormone also pushes the body to produce abnormally high levels of milk which can lead to early degeneration. Cows treated with BGH typically have short lives, and they are prone to mastitis, an infection of the udder, along with joint pain, and broken bones. The use of BGH is often reserved for the last few milking cycles before slaughter.
Some concerns have been raised about the impact of BGH on human health. Studies conducted on the hormone seem to indicate that it is species-specific, meaning that even if the hormone or its byproducts do end up in milk, this shouldn't affect human consumers. The United States Food and Drug Administration says that rBGH milk is identical to milk produced without the use of the hormone.
However, some people and regulatory agencies disagree. The European Union has banned the use of BGH in its cattle, and some consumers actively seek out milk which has been labeled as rBGH or rBST free. Commercial dairy producers and Monsanto have tried to fight such labels, arguing that they prejudice consumers, and they have been defeated numerous times in court.