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CHAPTER 39:THE MAMMARY GLAND (Colostrum (Passive immunity; high conc. of…
CHAPTER 39:THE MAMMARY GLAND
Control of Mammogenesis
Initial development by mammary mesenchyme
Puberty
Ducts: estrogen, GH & adrenal steroids
Alveoli: progesterone & prolactin
Colostrum
Prepartum milk secretion
Passive immunity; high conc. of Ig
produced by plasma cells from exposure to microorganism
Ig can be absorbed by neonatal gut only at first 24-36 hours of life
High in lipids (vit A), proteins (casein, albumin), low in carbohydrate (lactose)
lactose production is inhibited by progesterone
Lactogenesis
Prolactin
released w the manipulation of teats & vasoactive intestinal peptide
Fats are dispersed in droplet form
constriction of cell membrane, droplets often contain cell cytoplasm
Milk protein & lactose release from alveolar cells by exocytosis
milk protein → ER then to GA
lactose → Golgi apparatus
GH
Milk Removal
Oxytocin cause muscle contraction of myoepithelial cells
oxytocin stimulated by
tactile stimulation of suckling
manual stimulation of washing bfr milking
Ferguson reflex → stimulation of cervix
auditory, visual, olfactory stimuli
any sensory stimulus cow associates w milking
milk letdown → increased pressure within mammary gland bcs of contraction of myoepithelial cells
prolactin is ONLY stimulated by tactile stimulation of suckling
First Nursing
Carbohydrate stores:
-Good in singles/twins
-Low in litters
singles/twins can stand longer interval to first suckling: 1-2 hours w/o adverse effect
Litters tend to be immature at birth and susceptible to hypoglycemia
Composition of milk
Energy source: fats
monoglycerides, diglycerides, triglycerides, free fatty acids, phospholipids, steroids
Carbobhdrate: lactose
glucose & galactose
Protein: casein
casein may curd, other milk protein (albumin, globulin) remain in fluid [whey]
Lactation Cycle
Dairy cattle: peak at 1 month
dry-up at day 305 to prepare mammary gland for next lactation
Involution: stop milking → back pressure of milk within alveoli → inihibit secretion of milk by alveolar epithelial cells → regression of alveoli & small ducts
Can be induced by estrogen & progesterone, enhanced by GH & increase photoperiod exposure
Colostral milk
stringy & yellow
Disease associated
Mastitis (dairy cattle, dogs)
inflammation of gland
formation of CT limit proliferation of duct & alveoli
treatment often combine inflammatory & antibacterial agent
Passive transfer of RBC agglutinating antibodies to fetus through milk
common in horse
fetal RBC enter maternal system → antibody against fetal RBC
Hypocalcaemia: transient drain of calcium
increase mov. of Ca from blood to milk
lose ability to maintain normal muscle activity
inhibition of normal parathyroid gland development
systemic administration of Ca
Neoplasia (intact dogs, cats)
tumour
exposure to estrogen & progesterone