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Chapter 4

Chapter 4. Physiology of Milk Synthesis. FABP. MFGM. ACC. Milk Fat Synthesis. Circulation. Synthesis. Translocation. Secretion. UFA. TAG. LPL. NEFA. TAG. SFA. (C. -. C. ). 16. 18. +. synthesis. Glycerol. Glycerol. Glycerol. -. P. Glucose. Glucose. Acetate. de novo.

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Chapter 4

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  1. Chapter 4 Physiology of Milk Synthesis

  2. FABP MFGM ACC Milk Fat Synthesis Circulation Synthesis Translocation Secretion UFA TAG LPL NEFA TAG SFA (C - C ) 16 18 + synthesis Glycerol Glycerol Glycerol - P Glucose Glucose Acetate de novo FA synthesis (C - C ) 4 16 ßHBA FAS membrane ER membrane Luminal membrane Basal

  3. Epithelial Cell Lumen of alveolus Fat Droplet Fat Droplet migrating Golgi Body Lysosome Nucleus Mitochondria Mitochondria E.R. Blood Vessel

  4. Epithelial Cell Lumen of alveolus Fat Droplet Fat Droplet migrating Golgi Body Lysosome Nucleus Mitochondria Mitochondria E.R. Blood Vessel

  5. Epithelial Cell Lumen of alveolus Fat Droplet Cell pinches off Fat Droplet migrating Golgi Body Lysosome Nucleus Mitochondria Mitochondria E.R. Blood Vessel

  6. Epithelial Cell Lumen of alveolus Fat Droplet Cell pinches off Fat Droplet migrating Golgi Body Lysosome Nucleus Mitochondria Mitochondria E.R. Blood Vessel

  7. Major Fatty Acids (wt%) of Bovine Milk

  8. Major Fatty Acids (wt%) of Bovine Milk

  9. Major Fatty Acids (wt%) of Bovine Milk

  10. Changes in rumen conditions that lead to milk fat depression linoleic linoleic acid acid ( ( - - 9, 9, - - 12 C 12 C ) ) cis cis cis cis 18:2 18:2 conjugated conjugated linoleic linoleic acid acid conjugated linoleic acid - - 10, 10, - - 12 C18:2 trans trans cis cis ( ( - - 9, 9, - - 11 C18:2) cis cis trans trans vaccenic acid (trans-11 C18:1) - - 10 C 10 C trans trans 18:1 18:1 stearic acid (C18:0 )

  11. Milk Fat Concentration • Most variable component of milk • Increased during periods of energy deficit • Decreased when fed diets containing unsaturated fatty acids (most grains) and low effective fiber (change rumen conditions) • Milk fat depression (<2.8% fat) • Fatty acid changes also occur

  12. Milk Protein Concentration • Not too variable • Changes related to dietary energy intake, not dietary protein • little effect of dietary fat on milk protein concentration unless perturb normal rumen function • fermentable carbohydrate intake is the key! • Maximize VFA and microbial protein production

  13. Udder Pressure & Secretion Rate 1.5 1.0 Secretion Rate (kg/hr) (____) 0.5 0

  14. Secretion Rate • Influence of udder pressure • Milking intervals • 12 hour vs. other • 2X vs. 3X • young vs. old cows

  15. Yield and Milking Frequency(Erdman & Varner, 1995 JDS) Item Milk yield Fat% Protein % # studies 40 18 4 2X 42.9 3.65 3.10 3X 50.6 3.51 3.05 # studies 4 3 3 2X 54.6 4.71 3.49 4X 64.5 4.53 3.44

  16. Milk Let Down • Refractory period to oxytocin? • Adrenaline interferes

  17. Milk Ejection brain nerves P.P. Stimulus

  18. Milk Ejection nerves P.P.

  19. Milk Ejection P.P.

  20. Milk Ejection Abdominal aorta Oxytocin Jugular vein heart

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