On Nov. 5, 1993, Bovine somatotropin (BST) was approved by the U.S. Food and Drug Administration with the brand name ‘Posilac’ (sometribove zinc suspension) after determining that its use would be safe and effective.

BST is an animal drug used to increase milk production in dairy cows. This drug is based on the somatrotropin naturally produced in cattle. Somatotropin is a protein hormone produced in the pituitary gland of animals, including humans, and is essential for normal growth, development, and health maintenance.