Fungi Bacteria Protozoa Fungi 103ml 6 species Bacteria

Fungi Bacteria Protozoa

Fungi, ? 103/ml, 6 species Bacteria, 1010/ml, >>100 species Ciliates, 105/ml, >50 species

Fungi attached to fibre

Effect of p. H on rumen fermentation Hoover, 1986

단백질 에너지 = High Milk Urea 에너지 단백질 = Low Milk urea

Lactation

Fig 29 -2. The ligaments supporting the udder are shown in cross section (Courtesy of Iowa State University)

Milk Composition Species Cow Holstein Jersey Human Horse Pig Sheep Whale Total solids Fat Protein Lactose 12. 5 15. 0 12. 5 11. 0 19. 6 19. 9 57. 2 3. 5 5. 5 4. 4 1. 6 8. 3 8. 2 42. 3 3. 0 3. 9 1. 0 2. 7 5. 4 5. 8 12. 2 4. 8 7. 0 6. 1 5. 0 4. 8 1. 3

Cow's Milk Breed Table 4. Gross composition of milk of various breeds, g/100 g. Body Wt. (kg) Holstein 640 Brown Swiss 640 Ayrshire 520 Guernsey 500 Jersey 430 Shorthorn 530 Milk Yield (kg) 7360 6100 5760 5270 5060 5370 Fat Protein (%) 3. 54 3. 29 3. 99 3. 64 3. 95 3. 48 4. 72 3. 75 5. 13 3. 98 4. 0 3. 32 Lactose (%) 4. 68 4. 94 4. 60 4. 71 4. 83 4. 89 Ash (%) 0. 72 0. 74 0. 72 0. 76 0. 77 0. 73 Total Solids (%) 12. 16 13. 08 12. 77 14. 04 14. 42 12. 9 Holstein: 12. 16% T. S. x 7360 kg/lactation = 895 kg of total solids produced/lactation (140% of her body wt. !) Jersey: 14. 42% T. S. x 5060 kg/lactation = 730 kg of total solids produced/lactation (170% of her body wt. !)

Blood Flow l Milk synthesis controlled by two factors 1. Efficiency of nutrient extraction (genetics) 2. Volume of blood flow (genetics and hormones) - controlled by capillary sphincters - blood plasma volume increases by 30 -40% (from 3. 8 to 4. 9% of body weight)

Milk Synthesis Primer l Protein (3. 0%) l l Fat (3. 5%) l l l From amino acids Fatty acids from acetate and butyrate Long chain fatty acids from diet/body stores Lactose (4. 7%) l From glucose

Milk Synthesis - Protein l l Like all proteins, from amino acids Specific proteins are synthesized in the mammary gland Milk proteins Casein (80%) Whey β-lactoglobulin (10%) α-lactalbumin Serum albumin (4%) immunoglobulins (5%)

Composition of Milk Proteins l Caseins (80% of milk proteins) l phosphoproteins precipitated at p. H 4. 6 or by rennin l l l αs 1 αs 2 β κ γ 38% of total casein 10% of total casein 36% of total casein 13% of total casein

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

LIPIDS OR FATS Where do milkfat precursors come from? 1. Blood lipids: • diet and adipose tissue • lipoproteins (liver) • chylomicrons (gut) • free fatty acids / ketones 2. Glucose: glycerol fatty acids (non ruminants) 3. Acetate and butyrate (ruminants)