Milk Hygiene VM 361 Lecture Notes PDF

Milk Hygiene VM 361 Sunday, Tuesday 12:30-13:30 Dr. Abdalmajeed Alajlouni  Milk - Complex of organic and inorganic compounds where fat is present as emulsion, lactose and minerals as true solution, where as protein is present as colloid. - Normal secretion of...

Milk Hygiene VM 361 Sunday, Tuesday 12:30-13:30 Dr. Abdalmajeed Alajlouni  Milk - Complex of organic and inorganic compounds where fat is present as emulsion, lactose and minerals as true solution, where as protein is present as colloid. - Normal secretion of a normal mammary gland. - Hippocrates: “milk is the most nearly perfect food.” Milk is a rich source of nutrients – Almost nutrient perfect food. It provides protein of an excellent quality all essential amino acids twelve water soluble and four fat soluble vitamins lactose as energy source Increases the absorption of Ca  Milk Hygiene – All conditions and measures necessary to ensure safety and suitability of milk at all stages of the food chain. Milk safety – It is the assurance that Milk will not cause harm to the consumer. Milk Suitability – It is the assurance that Milk is acceptable for human consumption according to its intended use. Food chain (From Farm to Fork) – Steps that start at primary production and end at consumer table. Milk is synthesized in the mammary gland. – originated from secretary tissue of mammary gland and collected in series of ducts Lobe (cluster of alveoli) – Smallest production unit. – Spherical in shape.  The lobes constitute a quarter Four quarters comprise the udder of a cow. Separated by connective tissues and muscles. Mammary glands are supplied with a rich bed of blood vessels and nerves. Growth and Development of Mammary Glands structural and functional development of the mammary gland (lactogenesis) occurs in multiple cycles. cycles of development, functional differentiation, and regression. Hormonal and growth factor stimulation of mammary development during gestation facilitates the generation of abundant glandular alveoli. differentiation of epithelial cells of these alveoli leads to the onset of milk synthesis and secretion in conjunction with parturition  How Milk Is Made (biosynthesis of milk) Two important processes account for the secretion or making of milk (galactopoiesis) by mammary glands: 1- filtration of certain milk constituents from the blood stream 2- synthesis of other milk components by cellular metabolism within the alveoli Protein Milk proteins result from both filtration and synthesis casein, lactalbumin, and lactoglobulin found in milk are not present in blood (why)? occurs within the secretory epithelium in the alveoli Hormones essential for protein production are prolactin, insulin, and cortisol (hydrocortisone). Immunoglobulins and serum albumin identical in blood and milk Calves must receive colostrum soon after birth why?? Milk proteins synthesized in the rough endoplasmic reticulum processed through the Golgi complex, packaged into secretory vesicles, secreted from the apical surface by exocytosis. Biosynthesi of milk s  Lactose Glucose is a normal blood component two active glucose transport systems in mammary gland tissues Two molecules of glucose enter the secretory cell lactose synthetase for lactose synthesis. Lactose concentration in large part determines the volume of milk secreted ?? Hypoglycemic occur in high-producing cows in early lactation ?? Lactose may be derived also from short-chain fatty acids 20-30 %.  Fat More than half of bovine milkfat is synthesized in the mammary gland Triacylglycerol synthesized in the rough endoplasmic reticulum by acyltransferases. aggregate forming microlipid droplets released into the cytoplasm of the cell coated with proteins and polar lipids fuse forming larger droplets as they are transported to the apex of the cell A budding process results in expulsion of droplets from the cell. coated with more proteins and with phospholipids, forming an outer membrane (fat globule membrane)  In ruminants, acetate is the principal precursor Cows fed high-grain/low-forage rations commonly secrete low fat milk ?? Cows secrete milk low in fat during hot weather ??  Minerals minerals of milk are derived from the blood through filtration milk contains at least 10 times more calcium and phosphorus than blood decrease in lactose content there is a compensatory rise in the concentrations of sodium and potassium salts Salty milk in mastitis ?? Vitamins Vitamins filter directly from blood into milk B vitamins synthesized by ruminal microorganisms are rather constant in milk fat-soluble vitamins, especially vitamins A and D, are dependent upon quantities in the ration and body stores. Water Water is filtered from blood, depend on other contents of milk soilds. How Milk Is Discharged (Excreted) Is synthesis of milk during the interval between milking. Cells filling with milk then rupture and pour their contents into the lumen of an alveolus. mammary glands become engorged with milk, much as a sponge fills with water slowly flows out through ducts and gradually fills the entire duct system and the gland and teat cisterns. Cistern and duct system lined by elastic tissue elements, which permit great enlargement and expansion during the interval between milking.. Milk in all parts of the udder  Milking lead milk secretion Secretion progresses gradual rise in intra-mammary pressure leading: - increasing pressure of milk on blood capillaries reduces blood flow through the udder. - difficult for secreting cells to rupture and discharge their contents of milk into the lumina - fat accumulates within secreting cells, leading low fat milk slow milk secretion and discharge and may reabsorption. Milk secretion each hour following milking is approximately 90 to 95% of that of the preceding hour. In high-producing cows, milk secretion will essentially stop within 18 to 24 hours post-milking unless milk is withdrawn. why the last milk evacuated at milking time is higher in fat ?? Milk Letdown Removal of the milk by active participation of the neuroendocrine system. Involuntary reflex stimulated by: - mouth of a hungry calf - washing the mammary glands - hand milking - high internal udder pressure  Nervous system message to her brain oxytocin to be released from the posterior pituitary gland increase in intramammary pressure Increase in blood flow to the udder Vasopressin is released from the posterior pituitary Myoepithelial cells that surround the alveoli to contract squeezing the alveoli, causing milk letdown In cows teat storage capacity of 40 to 50 mL and each gland cistern storage capacity of 400 to 500 mL.