Submitted to: Encyclopedia of Dairy Science
Publication Type: Review Article
Publication Acceptance Date: October 3, 2001
Publication Date: January 1, 2003
Citation: Capuco, A.V., Akers, R. 2003. Galactopoiesis/effects of bst treatment. In: Roginski, H., Fuquay, J.W., Fox, P.F., editors. Encyclopedia of Dairy Science. London: Academic Press. p. 1458-1464.
In the 1930''s, injection of crude extracts from bovine anterior pituitary was shown to increase milk yield of dairy goats and cows. The component of these extracts that was responsible for increased milk production was later identified as somatotropin (growth hormone). Initial advances toward understanding the physiological effects of somatotropin were achieved using gpituitary-derived somatotropin, culminating in the concept that somatotropin orchestrates coordinated metabolic responses of tissues throughout the body to regulate nutrient partitioning and enhance milk production. This concept is known as "homeorhetic" control. With the production of recombinant bovine somatotropin (bST), it became feasible to utilize the hormone for increasing lactational performance of dairy cows. Subsequent research and commercial use expanded our knowledge of the physiological effects of bST and demonstrated its efficacy and safety as a stimulant of milk production. Indeed, somatotropin appears to be the primary galactopoietic hormone in mammals, except for rodents where prolactin appears to be dominant hormone. BST signaling pathways include direct signaling by bST and indirect signaling by insulin-like growth factors. Homeorhetic control is exerted in large part by altering the response to homeostatic signals. While bST exerts homeorhetic regulation, homeostatic regulatory processes that ensure animal well-being are still operative, and other homeorhetic mechanisms such as those to support body growth and those to support fetal development during pregnancy are still operative. Thus, bST exerts an overarching control, but not an overriding control, on processes that support milk production