What is rbST and How Does rbST Work?

Recombinant bovine somatotropin (rbST) works the same way as, and is a synthetic version of the protein, bovine somatotropin (bST), resulting in the production of just over one gallon more milk per cow per day.1

So, what is bST?

Bovine somatotropin, also referred to as bST or bGH or bovine growth hormone, is a naturally occurring protein hormone found in all dairy cattle. It is produced by the pituitary gland. The primary function of somatotropin is the coordination of nutrient use in the body to assure nutrients are used where they are most needed. In healthy lactating cows, it directs nutrients to the udder for milk production and in the young growing animal it makes nutrients available for growth. Somatotropin serves the same function in all mammals, including humans. Each mammalian species makes their own version of it.

How does rbST work?

When a dairy cow gives birth to her calf, she gradually produces more milk each day until she reaches her peak milk production level at about 60 days, at which time her milk production declines over time. rbST supplementation is initiated between day 57 and 70 of the lactation cycle. rbST supplementation helps cows prolong an improved level of milk production.

One cow produces enough milk in one day to provide milk for 125 kid’s school lunches. That same cow supplemented with rbST provides enough milk for about 145 children’s lunches.

History of rbST

rbST has been studied since the 1930s. The timeline below highlights key milestones in the research that’s been conducted on the use, efficiency and safety of rbST.

1930s: Russian scientists discover that when pituitary extracts of bST are injected into lactating dairy cows, milk production is increased.

1940s: English scientists try using pituitary extracts containing bST to increase milk per cow to address milk shortages during WWII. However, the attempt was abandoned due to insufficient supply of the extract.

1950s: Scientists at Harvard University gave children pituitary extract of bST in the hope of treating hypopituitary dwarfism. Conclusion: bST has no effect on humans.

1970s: Recombinant DNA technology is developed, leading to volume production of purified bST.

1982: Study of recombinantly produced bST is studied for its effects on milk production in lactating cows.

1982: Recombinantly produced human insulin (Humulin®) is introduced; it has the same activity as natural human insulin and is made by a process similar to that of rbST.

1984: The U.S. FDA determines that milk and meat from bST-supplemented cows are safe for human consumption.

1987: Recombinantly produced human growth hormone (human somatotropin or Humatrope®) is introduced to treat dwarfism in somatotropin-deficient children; it is made using a process similar to that of rbST. 2, 3

1990: rbST is approved for use in dairy cattle in Brazil and Mexico.4

1992: Studies find that rbST is environmentally sound.5

1993: The U.S. FDA approves rbST for use in U.S. dairy cattle.6

2008: Cornell University research documents that through the use of rbST to increase milk productivity, it reduces the carbon footprint of milk production which helps improve agricultural sustainability.7, 8

The Posilac product label (pdf)Link opens in a new window contains complete use information, including cautions and warnings. Always read, understand, and follow the label and use directions.

To increase production of marketable milk in healthy lactating dairy cows, supplement lactating dairy cows every 14 days beginning at 57–70 days in milk until the end of lactation.

1 Elanco data on file. Reference #1763. 10 Pound Executive Summary.

2 Humatrope® (somatotropin of recombinant DNA origin, Lilly).

3 Humulin® (human insulin of recombinant DNA origin, Lilly).

4 Avant for AFACT. Focus Groups Conducted to Understand Criteria for Dairy Food Purchases. December 6, 2007.

5 Johnson DE, Ward GM, Torrent J (1992) The environmental impact of bovine somatotropin use in dairy cattle. J Environ Qual 21:157–162.

6 Freedom of information summary: Posilac. 1993. Last accessed on March 1, 2009.

7 Capper JL et al. The environmental impact of recombinant bovine somatotropin (rbST) use in dairy production. Proc Natl Acad Sci USA. 2008 Jul 15;105(28):9668–73

8 Friedlander, B. Press Release: Carbon hoofprint: Cows supplemented with rbST reduce agriculture’s environmental impact. July 2008.

Recent Research

An independent assessment on rbST titled “Recombinant Bovine Somatotropin (rbST): A Safety Assessment,” was released in July 2009.