Dairy Cattle Lactation (Part 4) Flashcards
Milk secretion limiting factors
- Physical control (IM pressure)
- Chemical control (FIL)
How IM pressure limit milk secretion
From the accumulating milk (↓ blood flow , ↓ nutrients , ↓ release of cell contents).
How FIL pressure limit milk secretion
Inhibits the activity of the alveolar cells
It suppresses key enzymes in the epithelial cells
Is positive to milk production
Frequent removal of milk (3x milking)
Milk Letdown
Just prior to milking
40% of milk in the cisterns and large ducts
60% of milk in the alveoli and small ducts
Milk letdown is the moving of milk from
The alveoli and small ducts into the large ducts and cisterns where it can be removed
Milk let down is a …. reflex, and
is very important for maximum milk production
neurohormonal
1st step in milking routine
neurohormonal reflex
Positive Stimulation
Sight of a calf
Sound of a milking machine
Touch (Massage) of udder
Negative Stimulation
Inadequate udder preparation
Delayed attachment of teat cups
Physical pain
Fear
Positive Stimulation realsing
Oxytocin
Negative Stimulation realsing
Adrenalin
Interruption of Milk Letdown
Pain - Fear (loud noises, rough handling)
Release of adrenalin interferes with oxytocin inhibiting myoepithelial cell contraction
Adrenalin has a short half-life, and its effect dissipates in 20-30 min
Then, a cow can respond again to stimuli Of milk letdown
Poor ejection»_space; ↑ residual milk retained in the udder»_space; ↑ rapid buildup of IM pressure»_space; rate of milk secretion
Release of …. interferes with oxytocin inhibiting myoepithelial cell contraction
adrenalin
Residual milk (RM)
About 15 to 20% of total milk and 25 to 30% of the fat is retained in the udder after milking as RM (or complementary-milk)
To obtain residual milk
inject oxytocin and milk again
It is useful when treating mastitis to achieve maximum efficiency or antibiotics (less diluted by milk)
Lactose percentage
4.9%
Lactose Precursor
Glucose (Glucose + galactose)
Lactose Physical form
True solution
Lactose Site of synthesis
Golgi apparatus packaged into SV secreted by exocytosis
Protein %
3.4%
Protein Precursor
Blood free a.a
Protein Physical form
Caseins link together to form protein colloids called casein micelles (colloidal solution)
Protein Site of synthesis
rER packaged in Golgi apparatus into SV, secreted by exocytosis
Milk is in osmotic equilibrium with blood . Explain lactose role
Lactose responsible for 1/3 osmotic pressure
Lactose creates hypertonic solution within the SV thus water is drawn in
Lactose relation with milk amount
↑ Lactose → ↑ Milk amount
Explain how early lactating cow faces NEB
Early in lactation a high , producing cow may suffer hypoglycemia and develop ketosis from the increased mammary uptake of glucose for synthesis of lactose
Explain the salty taste of mastitis cow milk
Milk with :
Low amounts of lactose & K
High amounts of Na & Cl
The two major classes of milk proteins are …
casein and whey
+ small amount of NPN (urea)
Casein to whey ration in cows
80% : 20%
Casein to whey ration in humans
35% : 65%
Whey proteins include
ß-lactoglobulin
a-lactoglobulin
Serum albumin
Lactoferrin
Enzymes and protein hormones
Pre-formed proteins
Albumin & lgs from blood
Unlike humans the cows unable to transfer lgs to the fetus in utero; therefore, calves must receive colostrum soon after birth
Synthesized protein
ß-lactoglobulin
a-lactoglobulin
casein
enzymes and some Igs
…. not synthesized in Mammary glands
Serum albumin
