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MILK COMPOSITION

MILK COMPOSITION. Leo Timms Iowa State University. MILK COMPOSITION. Components are similar across species: - Water - Lactose (CHO) - Proteins - Lipids(fats) - Minerals - Vitamins Component % differ w/in & across species! Milk is greater than the sum of it’s parts!

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MILK COMPOSITION

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  1. MILK COMPOSITION Leo Timms Iowa State University

  2. MILK COMPOSITION • Components are similar across species: - Water - Lactose (CHO) - Proteins - Lipids(fats) - Minerals - Vitamins • Component % differ w/in & across species! • Milk is greater than the sum of it’s parts! • Emulsion of fat globules and a suspension of casein micelles (casein, Ca, P), all suspended in an aqueous phase which contains lactose, whey proteins, minerals, and salts.

  3. MILK COMPOSITION Lactose, whey, minerals, salts H20

  4. A. Fully differentiated alveolar epithelial cells characterized by presence of numerous vacuoles (V), rounded basally positioned nuclei (N), abundant cytoplasm, and frequent occurrence of large apically located lipid droplets (F); alveolar lumen is L. B. Intermediately differentiated alveolar epithelial cells showing fewer cellular vacuoles, more irregularly shaped nuclei, and greater nuclear to cytoplasmic ratio. C. Undifferentiated alveolar epithelial cells displaying relative absence of cellular vacuoles, highly irregularly shaped nuclei, a mixture of large and small lipid droplets, and very large nuclear to cytoplasmic ratio, (X4,000).

  5. ALVEOLUS

  6. ALVEOLUS

  7. ALVEOLUS

  8. MILK COMPOSITION Apical membrane Basement membrane

  9. MILK COMPOSITION RatCow Nucleus 22 22 RER 15 16 Golgi 21 19 Mito. 7 6 Lipid 1.5 5 Other 33.5 32

  10. MILK COMPOSITION

  11. SECRETION ROUTES Water urea glucose ions Membrane route

  12. SECRETION ROUTES Lactose casein whey prot. Citrate Ca Golgi route

  13. SECRETION ROUTES Fats hormones drugs Milkfat route

  14. SECRETION ROUTES Transcytosis

  15. SECRETION ROUTES Not common unless cells disrupted: mastitis! Paracellular: between cells Tight junction

  16. SECRETION ROUTES Membrane recycling pH: 6.2-6.9 Freeze pt.? < 32F (0C)

  17. MILK COMPOSITION

  18. MILK COMPOSITION WATER • Highest component except some marine • mammals! • Decreased viscosity so milk can be easily • removed from the gland by the neonate • Major source of water for neonates!!! • No resorbtion in ducts

  19. MILK COMPOSITION CARBOHYDRATES • LACTOSE • - primary milk CHO in most species • - unique to milk • - major osmole in milk • - least variable component? • - greatly impacted by mastitis • <1% - >7%: species differences

  20. MILK COMPOSITION CARBOHYDRATES* • mg / 100ml • LACTOSE 5000 (5%) • Glucose 14 • Galactose 12 • N- acetyl glucosamine 11 • Oligosaccharides

  21. LACTOSE • GLUCOSE is absolutely essential!!! • Can’t be replaced by any other sugar! • Lactose: uses 65-80% of total body • glucose in high producing animals • Correlation between milk production • and mammary glucose uptake = .93! WHERE DOES THE GLUCOSE COME FROM? * non ruminants - sugars, digestion of starch

  22. LACTOSE

  23. LACTOSE

  24. LACTOSE LIVER (glycogen storage) • Ruminant blood glucose levels 50% of monogas. • 45 - 60% of blood glucose from propionate • glucogenic amino acids, some lower GIT digestion

  25. (Locks glucose in cell) NADPH, RIBOSE (fat synth., DNA/RNA) ATP: not in ruminants GLYCEROL milkfat

  26. LACTOSE • Disaccharide • Glucose and galactose • UTP + Glucose UDP- glucose + P-P • UDP - glucose UDP galactose • (epimerase) • UDP - galactose + glucose lactose + UDP

  27. LACTOSE

  28. LACTOSE • Major enzyme complex: lactose synthase • Comprised of two enzymes • Galactosyl transferase • (widely present in many cells) • (transfers sugar moeities) • alpha lactalbumin • (specific to the mammary gland!!!) • gene expression increases w/lactogenesis • must continually be made: secreted in milk

  29. LACTOSE Draws in water

  30. LACTOSE • Milk is always isosmotic with blood!! • Lactose is major osmole but can change!

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