How did bovine somatotropin increase milk production in dairy cows?

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A step-by-step diagram shows donor DNA and vector DNA cut with restriction enzymes to create overhangs, mixed and sealed with ligase to form recombinant DNA, which is introduced into bacterial cells. The recombinant DNA replicates as the cells divide, producing clones. — biotechnology Steps involved in the engineering of a recombinant DNA molecule.

Bovine somatotropin (BST), also known as bovine growth hormone, is a naturally occurring protein produced in the pituitary gland of cattle. In the context of biotechnology, scientists developed a genetically engineered version known as recombinant bovine somatotropin (rbST) or recombinant bovine growth hormone (rBGH).1

When administered to dairy cows, rbST functions by stimulating the production of insulin-like growth factor 1 (IGF-1) in the liver. This process effectively redirects the cow's metabolic energy toward the mammary glands, thereby increasing the volume of milk produced. While this biotechnology was approved by the FDA in 1993 to enhance agricultural efficiency, its use has been a subject of debate due to concerns regarding animal welfare, specifically an increased risk of mastitis in treated cattle and the subsequent necessity for antibiotic use.1