Bovine somatotropin

Bovine somatotropin, also called bovine growth hormone or BST, is a peptide hormone produced naturally by the pituitary gland of cattle; a synthetic version, rBST, is injected into dairy cows to raise milk production by roughly 10 percent. The United States Food and Drug Administration approved rBST in 1993, but it remains controversial over animal welfare concerns and has been banned in the European Union since 1990 and is also prohibited in Canada, Japan, Australia, New Zealand and Argentina; the Codex Alimentarius has not approved it as safe. The FDA has stated that no significant difference has been shown between milk from rBST-treated and untreated cows, and it has discouraged marketing milk as bST-free to avoid misleading consumers.