Cows naturally produce bovine somatotropin (bST) in their pituitary gland; it directs how energy and nutrients are used for growth in young cattle and for milk production in lactating cows. Dairy farmers may choose to use rbST to help cows produce more milk. In either situation - whether bovine somatotropin (bST) produced by the cow or by recombinant DNA technology (rbST) - no differences can be detected in the animal or the milk produced by that animal.