Dairy Cattle Lactation (Part 2)

Question 1

Control of lactogenesis
High P4 During pregnancy

Answer 1

blocks lactogenesis i.e a drop in P4 level before parturition a prerequisite for lactogenesis

Question 2

Control of lactogenesis
↑ PG before parturition

Answer 2

Lysis of CL → ↓ P4 level

The mammary gland becomes free to response to the hormones of the lactogenic complex (chiefly glucocorticoids and PRL)

Question 3

Control of lactogenesis
↑ E2 (placental) before parturition

Answer 3

↑ PRL secretion

Question 4

Control of lactogenesis
Placental ACTH

Answer 4

↑ glucocorticoids

Question 5

Control of lactogenesis
A surge in GH occurs before parturition

Answer 5

direct nutrients to the mammary gland for milk synthesis

Question 6

PRL and glucocorticoids induce

Answer 6

Dramatic maturation of alveolar organelles resulting irvsynthesis of proteinv fat and lactose

Question 7

Galactopoiesis

Answer 7

To continue lactation (galactopoiesis), number and activity of alveolar cells must be maintained

Question 8

Two interrelated factors contribute to maintenance of lactation

Answer 8

Hormones + removal of accumulated milk

Question 9

Primary galactopoietic hormone in Non-ruminants

Answer 9

PRL

Question 10

Primary galactopoietic hormone in Ruminants

Answer 10

GH / PRL is minor

Question 11

…. are required for maintenance of lactation

Answer 11

PRL, glucocorticoids and GR

They are released in response to milking or suckling

Question 12

Exogenous PRL effect in milk

Answer 12

Did not affect milk yield of lactating dairy cows, but small increase in milk production was realized in dairy goats

Question 13

Biweekly administration of rbST (recombinant GH) results in

Answer 13

about 10% higher milk yield

GH does not direct stimulate the mammary gland but causes a flux of nutrients to the mammary gland for synthesis of milk

Question 14

…. causes involution (regression) of the mammary glands

Answer 14

Cessation of milking or suckling

Question 15

Secretory activity is decreased due to

Answer 15

Physiologically
Structurally

Question 16

Secretory activity is decreased due to Physiologically

Answer 16

↑ intramammary pressure (IMP)
the feedback inhibitor of lactation (FL) which when milk been for while → ↑ FL secretion

Question 17

Secretory activity is decreased due to Structurally

Answer 17

There is little loss of alveolar structure a decrease in cytoplasmic organelles and a decrease in intra-alveolar area

Question 18

Biosynthesis and Secretion of Milk

Answer 18

Milk is secreted in the interval between milkings

A Site of milk synthesis → The epithelial cells lining the alveoli

Question 19

Alveoli (Acini)

Answer 19

Myoepithelial cells around secretory alveoli in lactating mammary gland seen in the scanning EM , Blood capillaries (C) and fibroblasts

Question 20

Explain how Cells does not synthesize milk?

Answer 20

Cells synthesizes milk components and send it to lumen

Question 21

High blood levels of oxytocin reached …..

Answer 21

30 s after beginning of stimulation

Question 22

Why rapid attachment of milking machine and rapid milking are important ?

Answer 22

High blood levels of oxytocin reached 30 s after beginning of stimulation

The effect of oxytocin lasts for a few minutes

Question 23

Rapid attachment of milking machine … after teat stimulation

Answer 23

60-90 seconds