rBST, or recombinant bovine somatotropin, is a synthetic form of bovine somatotropin (BST), a growth hormone, used to increase milk yield in dairy cows.
Milk from rBST treated cows may have higher levels of BST and insulin-like growth factor 1 (IGF1) than traditional milk. BST is found in milk from rBST and non-rBST treated cows, as it is a naturally occurring hormone; BST is degraded by the human digestive system. IGF1 is a growth factor that is not destroyed by pasteurization and may be absorbed in the digestive tract. rBST treated cows also typically require more antibiotics than their untreated counterparts.
rBST use labeling is not mandatory in America, where the hormone is regulated but not prohibited. It is prohibited in Canada due to concerns for animal health.
Milk, yogurt, other dairy products
Bovine somatotropin, BGH, bST, recombinant bovine growth hormone, rBGH