Transcript milk composition - Iowa State University: Animal Science Computer

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!
• 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.
MILK COMPOSITION
Lactose, whey,
minerals, salts
H 20
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).
ALVEOLUS
ALVEOLUS
ALVEOLUS
MILK COMPOSITION
Apical membrane
Basement
membrane
MILK COMPOSITION
Rat
Cow
Nucleus 22
22
RER
15
16
Golgi
21
19
Mito.
7
6
Lipid
1.5
5
Other 33.5
32
MILK COMPOSITION
SECRETION ROUTES
Water
urea
glucose
ions
Membrane route
SECRETION ROUTES
Lactose
casein
whey prot.
Citrate
Ca
Golgi route
SECRETION ROUTES
Fats
hormones
drugs
Milkfat
route
SECRETION ROUTES
Transcytosis
SECRETION ROUTES
Not common
unless cells
disrupted:
mastitis!
Paracellular:
between cells
Tight
junction
SECRETION ROUTES
Membrane
recycling
pH: 6.2-6.9
Freeze pt.?
< 32F (0C)
MILK COMPOSITION
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
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
MILK COMPOSITION
CARBOHYDRATES*
mg / 100ml
•LACTOSE
5000 (5%)
• Glucose
14
• Galactose
12
•N- acetyl glucosamine 11
• Oligosaccharides
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
LACTOSE
LACTOSE
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
(Locks glucose in cell)
NADPH, RIBOSE
(fat synth., DNA/RNA)
ATP:
not in
ruminants
GLYCEROL
milkfat
LACTOSE
• Disaccharide
• Glucose and galactose
• UTP + Glucose
UDP- glucose + P-P
• UDP - glucose
UDP galactose
(epimerase)
• UDP - galactose + glucose
lactose + UDP
LACTOSE
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
LACTOSE
Draws in water
LACTOSE
• Milk is always isosmotic with blood!!
• Lactose is major osmole but can change!