Bovine somatotropin
- RBST redirects here. For information on the computational algorithm, see RBST (algorithm).
Bovine somatotropin (bST), or bovine growth hormone (BGH), is a protein hormone that occurs naturally in the pituitary gland of cattle. It is a factor controlling the amount of milk produced by a dairy cow. Bovine somatotropin is naturally in the milk extracted from a cow.
Physiology
Because of protein homology, bovine growth hormone (GH) cross-reacts with the receptors of prolactin and placental lactogen — two hormones that stimulate mammary tissue to produce more milk.
Somatotropin and somatropin both refer to growth hormone (GH), a protein hormone produced by the mammalian pituitary. The genes for GH, the amino acid sequence of the peptides, the receptor genes, and the receptor structures are recognizably homologous, though cross-species differences are significant enough to prevent most cross-species effects (i.e. bST does not "work" in humans).
Although bST, insulin-like growth factor 1 (IGF1), and other cow hormones can be measured in cow milk, it is thought that the amounts are too small and digestion too complete for them to have any effect in humans.
Synthetic bST
Monsanto developed a synthetic version of bST, known as recombinant bovine somatotropin (rbST), which goes by the brand name Posilac®. Injected into dairy cattle, the product can increase milk production by anywhere from an average of 10% up to 40%. In November 1993, the product was approved for use in the U.S. by the FDA, and its use began in February 1994. The product is now sold in all 50 states. According to Monsanto, approximately one third of dairy cattle in the U.S. are injected with Posilac; approximately 13,000 dairy producers use the product. It is now the top selling dairy cattle pharmaceutical product in the U.S. The FDA does not require special labels for products produced from cows given rbST.
However, use of the synthetic supplement has been controversial. Many people claim not enough research has been done into human health effects; some fear increased risk of cancers, diabetes, and hypertension in consumers of products from rbST injected cows. Other fears include health problems for the injected cattle, and an economic concern for small farmers due to the increased supply of milk.
According to Monsanto, milk and meat from cattle supplemented with rbST are safe. Monsanto also states that the only difference between milk from supplemented cattle and unsupplemented cattle is the amount of IGF1 — and that there is not even a difference in the concentration of bST.
In 1998, a Canadian committee found that while there were no significant risks to human health, there are increased risks to animal safety due to injections of rbST. According to their report, use of rbST increased the risk of mastitis by up to 25%, of infertility by 18%, and of lameness by up to 50%. Humans who have too much growth hormone develop a disease called acromegaly, and some speculate that it is no more healthy for cows to have too much growth than it is for humans. Many animal rights activists oppose any farming practice that seems to "industrialize" food production from animals in an artificial way.
Milk production in North America, Europe, and Australia is already plentiful and milk is relatively inexpensive, so those opposing the use of the drug have expressed concerns that using the drug to increase milk production (hence depressing prices) primarily benefits large scale producers, and will narrow the margins that small dairy farms receive for their products. Whether this is problematic or not is an economic debate.
Politics
- In the United States, the use of rbST is permitted.
- In Canada, the use of rbST has not been approved.
- The European Union declared the use of rbST as safe in 1990, but in 1993, a moratorium was placed on its sale.