Physiology of colostrum production.

Area of Science:

• Endocrinology
• Animal Reproduction
• Lactation Physiology

Background:

• Mammary gland development, colostrum secretion, and lactogenesis in cows and sows are regulated by endocrine equilibrium during gestation and lactation.
• Hormonal sequences, including ovarian, fetoplacental, pituitary, and adrenal hormones, are essential for mammary gland development.
• Specific milk product synthesis, like caseins and lactose, remains low during pregnancy and increases sharply post-calving/farrowing.

Purpose of the Study:

• To elucidate the hormonal regulation of mammary gland development and function in cows and sows.
• To understand the hormonal milieu surrounding parturition and its role in colostrum secretion and IgG1 uptake.
• To investigate the effects of specific hormone administrations on mammary gland development and function in non-pregnant animals.

Main Methods:

• Observation of hormonal level variations during gestation, parturition, and lactation.
• Administration of ovarian steroids (estrogens, progesterone) and other hormones (corticoids, prolactin) to non-pregnant, dried cows.
• Induction of calving using dexamethasone and/or estradiol benzoate to study colostrum secretion.
• Analysis of mammary gland structure, hormone receptor appearance, and protein uptake.

Main Results:

• Hormonal sequences involving estrogens, progesterone, prolactin, and corticoids drive mammary gland development to near completion by parturition.
• Colostrum secretion coincides with a sharp drop in progesterone and a rise in estrogens, followed by increased prolactin and corticoids.
• Estrogens are crucial for epithelial cell proliferation and IgG1 receptor appearance, while their withdrawal, along with prolactin and corticoids, initiates colostrum secretion and milk production post-parturition.

Conclusions:

• Precise endocrine regulation governs mammary gland development, colostrum production, and the initiation of lactation in cows and sows.
• The hormonal environment around parturition, characterized by decreasing progesterone and increasing estrogens, prolactin, and corticoids, is critical for successful transition to lactation and immune transfer via colostrum.
• Hormonal manipulation can induce mammary gland development and colostrum secretion, offering insights into the physiological mechanisms involved.