1 / 20

Lactation Physiology (part 2)

فیزیولوژی تولید و ترشح شیر. Lactation Physiology (part 2). By: A. Riasi (PhD in Animal Nutrition & Physiology). Physiology of mammary gland during the dry period. During dry period the gland has three distinct functional states: The period of active involution

nellie
Download Presentation

Lactation Physiology (part 2)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. فیزیولوژی تولید و ترشح شیر Lactation Physiology(part 2) By: A. Riasi (PhD in Animal Nutrition & Physiology)

  2. Physiology of mammary gland during the dry period • During dry period the gland has three distinct functional states: • The period of active involution • The period of steady state involution • The period of lactogenesis and colostrogenesis: • Regeneration and differentiation of secretory epithelial cells • Selective transport and accumulation of immunoglobulin • The onset of copious secretion

  3. Physiology of mammary gland during the dry period • The mammary gland undergoing transition at two stages: • At the beginning of the dry period • At the end of the dry period

  4. Physiology of mammary gland during the dry period • Reducing the length of the dry period of dairy cows may affect: • Postpartum health • Reproduction performance • Milk production

  5. Physiology of mammary gland during the dry period • Intra-alveolar pressure triggers the events of active involution: • The appearance of lysosomes in the secretory epithelial cells. • Macrophages enter the mammary tissue and secretion. • The rate of synthesis of major milk constituents decrease: • Fat • Casein • Lactose * • Citrate * • β-lactoglobulin • α-lactalbumin

  6. Physiology of mammary gland during the dry period • By 7 days involution, the concentration of serum proteins in mammary secretion is significantly elevated. • The permeability barriers are not totally destroyed and the mammary gland maintains a degree of control.

  7. Physiology of mammary gland during the dry period • The concentration of the iron biding protein lactoferrin (Lf) dramatically increase. • The major site of synthesis of the Lf found in bovine mammary secretions is thought to be the secretory epithelial cell. • Lf is a major protein in the secretion of the non-lactating mammary gland. • Lactoferrin is bacteriostatic by virtue of its ability to bind iron with great affinity.

  8. Development of the Mammary Gland (Mammogenesis) • Mammary gland has allometric and isometric growth • The development of mammary growth has five phases: • Fetal phase • Prepubertal phase • Postpubertal phase • Pregnancy • Lactation

  9. Development of the Mammary Gland (Mammogenesis)

  10. Development of the Mammary Gland (Mammogenesis)

  11. Development of the Mammary Gland (Mammogenesis) • Prepubertal mammary growth begins as isometric growth, and before puberty becomes allometric. • A large portion of mammary growth before puberty is an increase in: • Connective tissue • Ductal growth • Growth of the fat pad

  12. Development of the Mammary Gland (Mammogenesis) • Feed restricted heifers can have up to 30 percent larger mammary glands at puberty. • Studies have also shown that feeding high energy diets during the prepubertal period suppresses serum bovine somatotropin (bST) levels.

  13. Development of the Mammary Gland (Mammogenesis) • Through the first several estrous cycles after puberty, rapid mammary growth continues. • Most of the growth is lost through regression during the luteal phase of each estrous cycle. • Nutrition plays an important, though controversial, role in postpubertal mammary development.

  14. Development of the Mammary Gland (Mammogenesis) • Mammary growth is a continuous, exponential process from conception to parturition • The greatest increase occurs in mass of parenchymal tissue in late pregnancy. • The increasing udder size during the fifth and sixth months of pregnancy is due to: • The elongation of mammary ducts • The formation of alveoli • The reduction of identifiable fat cells in the fat pad

  15. Development of the Mammary Gland (Mammogenesis) • Mammary growth continues in early lactation. • Persistency of lactation (maintaining peak milk yield) depends on the continual survival of those milk-secreting cells. • In rats, increases in total mammary DNA was seen from parturition until weaning.

  16. Hormonal control of mammogenesis • The ovarian steroids are important for mammogenesis. • Ovarioectomy affect the parenchyma tissue of mammary gland. • The ovarian activity appears to mediate the actions of GH.  • Effect of Prl and PL on mammogenesis in some species

  17. Hormonal control of mammogenesis • Mammogenesis depends not only on hormonal concentration but also on: • Receptor availability within the mammary tissue • The presence of transport proteins and intracellular lipids that are capable of making steroids unavailable to the tissues.

  18. Hormonal control of mammogenesis • Several other hormones play a permissive and supportive role in mammary growth: • Placental lactogens • Adrenal gland hormones • Thyroid hormones • Relaxin • Parathyroid hormone • Effect of parathyroid hormone-related protein (PTHrP)

  19. Hormonal control of mammogenesis • Other factors that may affect mammogensis: • Insulin-like growth factors (IGF) • Epidermal cell factors (ECF) • Transforming growth factors (TGF) • Fibroblast growth factors (FGFs)

More Related