Mammary gland involution in cows

Mammary gland involution in cows occurring in the last trimester of pregnancy is an important physiological process for quick fetus growth, the correct course of parturition and post parturient period, adequate fertility and high milk production in subsequent lactation. Secretion volume declines during involution, as does the concentration of most milk-specific components (casein, lactose, fat, citrate, alpha-lactoalbumin, beta-lactoglobulin). Somatic cell count, lactoferrin, hydrolytic enzymes, immunoglobulins, serum, albumins and other serum-derived components increase in concentration. Microscopic examination of mammary tissue indicated a gradual reduction in synthetic and secretory activity of alveolar,epithelium as involution progressed. Light, microscopic, morphologic analysis revealed increases, in stroma and nonactive secretory epithelium, with concomitant decreases in epithelium, lumen, and fully active secretory epithelium during the first, 2 weeks of involution. Electron microscopic analysis of alveolar epithelium,revealed a decreased number of organelles associated with milk synthesis and secretion during this time. Involution is characterized by, de-differentiation and apoptosis of mammary epithelial cells. The involution and evolution of the mammary gland is controlled by prolactin, growth hormone estrogens, progesterone, cortisol and insulin-like growth factor 1 (IGF-1). T1 he plasminogen and plasmin system is involved in the involution. Elevated plasmin activity is primarily responsible for the observed concurrent hydrolysis of milk proteins in mammary secretions. Peptides detected during involution were generated from alpha s-casein, beta-casen, kappa-casen, or lactoferrin. Casein hydrolyzates cause the disruption of tight junction integrity and induce involution. Prolactin and growth hormone play a specific role in mammary gland ipoptosis through insulin-like factor 1.(IGF1) that is modulated by a family of binding proteins (BPs), especially IGFBP-5.