galactopoiesis
Lactation initiation is a continuous process post-parturition, persisting until peak yield and lactation establishment. Galactopoiesis denotes the maintenance of lactation or milk secretion.
Key factors responsible for lactation maintenance include milk synthesis and secretion, milk removal, and adequate release and action of galactopoietic hormones. Milk synthesis and secretion are closely interlinked, with impaired synthesis if milk isn’t removed from the udder during milking. Growth hormone, prolactin, thyroid hormone, insulin, and adrenal corticoids play vital roles in milk secretion, albeit with species-specific differences. Galactopoiesis terminology often indicates lactation enhancement in dairy animals due to galactopoietic hormones. Evaluating substances or hormones as galactopoi- etic agents involves two methods:1. Suppression of plasma hormone concentration to observe effects on milk production and composition. A decline in milk yield indicates the hormone’s necessity for lactation maintenance, with effects varying by species, lactation stage, and parity.
2. Exogenous hormone administration during lactation to enhance milk production, indicating the hormone’s role as a rate-limiting factor in milk secretion. From different studies, even some non- hormonal preparations and herbal products like shatavari, guduchi, protected choline chloride, protected amino acids, or prill fat augment milk production in cows and buffaloes, acting as galac- tagogue substances.
The mammary gland comprises numerous epithelial cells and alveoli in varying functional states during lactation stages. Dynamic changes occur in mammary glands during lactation, extensively studied in goats. Milk yield typically increases after parturition, peaking around 45 days in cows and buffaloes. Persistence varies among individuals, with some reaching peak yield early and others later.
Factors influencing milk yield include nutrient availability, metabolic state, management, and environment, particularly pronounced during lactation phases. Late pregnancy’s programmed cell death, apoptosis, leads to decreased milk secretion. Augmenting milk production involves maintaining alveolar cell number, synthetic activity per mammary cell, milk ejection reflex efficacy, using galactagogues substances, and balancing cow feeding based on milk yield. Galactopoietic hormones effectively influence milk yield when milk ejection is complete and frequent milk removal occurs. Inefficient removal despite adequate hormonal status leads to discontinued milk synthesis. Maintenance of lactation necessitates both milk secretion and removal. Qualitative changes in milk yield, mammary secretory cell count, and milk yield per epithelial cell are extensively studied in goats. Mammary DNA increases during early lactation in goats due to continued lactogenic enzyme activity and increased secretory cell differentiation. In dairy cattle, mammary DNA increases during early lactation, but precise postpartum mammary growth timing and extent remain undefined. Mammary cell count changes and milk yield per cell are regulated by galactopoietic hormones and local mammary factors.22.13.1 Hormonal Regulation of Galactopoiesis
Hormones released from various sources regulate the maintenance of lactation in both ruminants and non-ruminants.
• Adrenal gland (glucocroticoids and mineralocorticoids)
• Ovary (estrogen)
• Oxytocin (essential for let down of milk)
• Pituitary gland (prolactin, GH, ACTH, TSH)
• Thyroid gland (I, & T) - Mammary glands local growth factors
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