|Akers, Michael - VPI&SU|
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, M.R. 2003. Galactopoiesis/effect of hormones and growth factors. In: Roginski, H., Fuquay, J.W., Fox, P.F., editors. Encyclopedia of Dairy Science. London: Academic Press. p. 1452-1458. Technical Abstract: The term galactopoiesis was originally coined to describe the enhancement of an established lactation. In this sense, only exogenous ST and thyroid hormone are demonstrated galactopoietic agents in dairy animals, suggesting these hormones are endogenously rate limiting. However, galactopoiesis is used more inclusively to describe the maintenance of lactation. Many hormones and factors are involved in maintaining milk production in dairy animals and these are described in this review. Galactopoietic hormones, growth factors, and regular milk removal are essential for regulation and maintenance of lactation. The pituitary and its hormones are essential integrators of endocrine regulation of milk secretion, but milk production of hypophysectomized goats can be fully restored to prehypophysectomy levels by the combined administration of prolactin (PRL), somatotropin (ST), glucocorticoids and triiodothyronine. Although there clearly are species differences, PRL, ST, glucocorticoids and thyroid hormones are typically required for full maintenance of lactation. Still, additional hormones and growth factors (both humoral and local, identified and unidentified) are probably important for the normal physiological maintenance of lactation. In addition to factors that actively support synthesis of milk components, frequent emptying of the gland is critical. Physiological support for both milk synthesis and removal is necessary. Other factors that can affect the maintenance of lactation are those that enhance the maintenance of the secretory cell population by decreasing cell loss or by increasing cell proliferation. These factors do not impact the secretory capacity of existing cells but impact the secretory capacity of the mammary gland, the shape, and length of the lactation curve.