Dairy Cattle Lactation (Part 4)

Question 1

Milk secretion limiting factors

Answer 1

1. Physical control (IM pressure)
2. Chemical control (FIL)

Question 2

How IM pressure limit milk secretion

Answer 2

From the accumulating milk (↓ blood flow , ↓ nutrients , ↓ release of cell contents).

Question 3

How FIL pressure limit milk secretion

Answer 3

Inhibits the activity of the alveolar cells

It suppresses key enzymes in the epithelial cells

Question 4

Is positive to milk production

Answer 4

Frequent removal of milk (3x milking)

Question 5

Milk Letdown

Answer 5

Just prior to milking

40% of milk in the cisterns and large ducts
60% of milk in the alveoli and small ducts

Question 6

Milk letdown is the moving of milk from

Answer 6

The alveoli and small ducts into the large ducts and cisterns where it can be removed

Question 7

Milk let down is a …. reflex, and
is very important for maximum milk production

Answer 7

neurohormonal

Question 8

1st step in milking routine

Answer 8

neurohormonal reflex

Question 9

Positive Stimulation

Answer 9

Sight of a calf
Sound of a milking machine
Touch (Massage) of udder

Question 10

Negative Stimulation

Answer 10

Inadequate udder preparation
Delayed attachment of teat cups
Physical pain
Fear

Question 11

Positive Stimulation realsing

Answer 11

Oxytocin

Question 12

Negative Stimulation realsing

Answer 12

Adrenalin

Question 13

Interruption of Milk Letdown

Answer 13

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&raquo_space; ↑ residual milk retained in the udder&raquo_space; ↑ rapid buildup of IM pressure&raquo_space; rate of milk secretion

Question 14

Release of …. interferes with oxytocin inhibiting myoepithelial cell contraction

Answer 14

adrenalin

Question 15

Residual milk (RM)

Answer 15

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)

Question 16

To obtain residual milk

Answer 16

inject oxytocin and milk again

It is useful when treating mastitis to achieve maximum efficiency or antibiotics (less diluted by milk)

Question 17

Lactose percentage

Answer 17

4.9%

Question 18

Lactose Precursor

Answer 18

Glucose (Glucose + galactose)

Question 19

Lactose Physical form

Answer 19

True solution

Question 20

Lactose Site of synthesis

Answer 20

Golgi apparatus packaged into SV secreted by exocytosis

Question 21

Protein %

Answer 21

3.4%

Question 22

Protein Precursor

Answer 22

Blood free a.a

Question 23

Protein Physical form

Answer 23

Caseins link together to form protein colloids called casein micelles (colloidal solution)

Question 24

Protein Site of synthesis

Answer 24

rER packaged in Golgi apparatus into SV, secreted by exocytosis

Question 25

Milk is in osmotic equilibrium with blood . Explain lactose role

Answer 25

Lactose responsible for 1/3 osmotic pressure
Lactose creates hypertonic solution within the SV thus water is drawn in

Question 26

Lactose relation with milk amount

Answer 26

↑ Lactose → ↑ Milk amount

Question 27

Explain how early lactating cow faces NEB

Answer 27

Early in lactation a high , producing cow may suffer hypoglycemia and develop ketosis from the increased mammary uptake of glucose for synthesis of lactose

Question 28

Explain the salty taste of mastitis cow milk

Answer 28

Milk with :
Low amounts of lactose & K
High amounts of Na & Cl

Question 29

The two major classes of milk proteins are …

Answer 29

casein and whey
+ small amount of NPN (urea)

Question 30

Casein to whey ration in cows

Answer 30

80% : 20%

Question 31

Casein to whey ration in humans

Answer 31

35% : 65%

Question 32

Whey proteins include

Answer 32

ß-lactoglobulin
a-lactoglobulin
Serum albumin
Lactoferrin
Enzymes and protein hormones

Question 33

Pre-formed proteins

Answer 33

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

Question 34

Synthesized protein

Answer 34

ß-lactoglobulin
a-lactoglobulin
casein
enzymes and some Igs

Question 35

…. not synthesized in Mammary glands

Answer 35

Serum albumin