Lactogenesis (Milk Secretion)

• Concentration of estrogen and progesterone secreted by ovaries and placenta during pregnancy increases.
• It leads to development of mammary gland and prolactin level decreases.
• After parturition,prolactin increases and progesterone level decreases.
• Initiation of lactation then takes place later.

Note: For every liter of milk secreted, 500 liter of blood is required.

Galactopoiesis (Maintenance of Lactation)

• After parturition, there is rapid increase in milk yield in cow upto 2-6 weeks.
• Milking/suckling stimulus and intra mammary pressure induce it.
• Milking releases hormones required for lactation.
• If milking is stopped, synthesis stops and the secretory cells of the udder are rapidly lost.
• Milking causes release of prolactin from anterior pituitary which helps to maintain lactation which further releases ACTH and oxytocin.
• Somatotropin ejection cause a marked increase inn milk production of lactating cows.
• Iodocaesin artificially induce milk production.
• Thyroxin contains less iodine and are given orally to ruminants for increasing milk production.
• Feeding high calorie diet to cow before first calf reduce the milk yield and causes deposition of high fat inn udder.
• Under feeding cause delayed sexual maturation.

Milk Ejection (Milk Letdown)

• Letdown of milk is controlled by neuro hormonal action when udder influences the hormone.
• Suckling causes sensory impulses to rise in nerve ending of teat.
• Hypothalamus is stimulated and release the oxytocin.
• Blood reaches udder where oxytocin cause contraction of myoepithelial cells.
• Contraction of alveoli forces milk to collecting ducts.
• Milk is then removed by milking or suckling within 7-15 minutes.