Ex 3 - Mammary Gland and Lactation

Question 1

How does growth occur from birth to puberty?

Answer 1

isometric growth

Question 2

Development during puberty - long cycle mammals

Answer 2

Duct develops under the influence of E2, prolactin, and GH –> alveoli and lobules develop under influence of P4

Question 3

Development during puberty - short cycle mammals

Answer 3

No alveoli or end buds develop until pregnancy

Question 4

Development during pregnancy

Answer 4

Constant high levels of P4, E2 and placental lactose

Growth of mammary glands occurs slowly in early pregnancy, ten becomes exponential in late term pregnancy

Question 5

Development during lactation

Answer 5

mammary development ceases in most animals (except cattle)

Question 6

P4 effects on milk production

Answer 6

P4 has INHIBITORY effects on milk production

Question 7

What 3 hormones have stimulatory effects on milk production?

Answer 7

E2, prolactin, and placental lactogen

Question 8

What stimulates milk production?

Answer 8

prolactin

Question 9

What stimulates milk ejection (let down)?

Answer 9

Oxytocin

Question 10

What inhibits milk ejection?

Answer 10

epinephrine –> if the dam is stressed, she won’t be able to nurse her baby!

Question 11

What triggers a decrease in milk production?

Answer 11

GH! Decrease in GH –> dec in prolactin

Question 12

How can we increase length of lactation?

Answer 12

Administer exogenous GH

Question 13

How does mammary gland involution occur? (drying-up)

Answer 13

Not milked for a few days –> increased hydrostatic pressure –> fluid absorbed –> reduction in milk synthesis

Absence of tactile stimulation and prolactin release

*Recommend 30 day dry period (45 days is ideal)

Question 14

Cows vs heifers - milk production

Answer 14

Heifers have a flatter lactation curve when compared to cows –> stay in milk longer

Question 15

Cows and goats increase in milk production up to ____ lactations

Answer 15

4

Question 16

______ is the only CFA that can be used to make glucose in ruminants

Answer 16

Proprionate

Question 17

Ruminants have very high glucose demands during late pregnancy and lactation… how can they adapt to handle this?

Answer 17

• lower baseline insulin levels
• dec peripheral glucose uptake –> fat-based peripheral energy metabolism
• glucose sparing for fetus, mammary gland and brain

Question 18

Milk fat triglycerides and FA synthesis

Answer 18

Ruminants cannot use glucose for FA synthesis

They use: acetate (VFA), lactate, and 3-OHbutyrate

Question 19

What is A2 milk?

Answer 19

beta-casein protein that differs by one aa from A1 (A1 found in majority of milk)

A2 is a recessive trait

Lactose intolerance is lessened if consuming A2 milk

Question 20

Colostrum

Answer 20

Secretion is mostly IgG from serum

Selective transfer of Ig via specific receptors

Some local production of IgA and IgM, and local lymphocytes

Question 21

How is colostrum absorbed in the neonate?

Answer 21

Via enterocytes

Question 22

Failure of passive transfer - causes

Answer 22

poor quality due to poor immunity of dam 
failure to secrete due to illness 
loss due to leakage 
differences based on breed 
failure to consume 

Supplementation is NECESSARY in cases in FPT

Question 23

What causes Ergotism in mares?

Answer 23

Fescue grass –> toxin is a DOPAMINE agonist –> inhibits prolactin secretion

Results in: prolonged gestation and agalactia

*Tx: give domperidone (dopamine antagonist)

Question 24

What hormone INHIBITS prolactin?

Answer 24

Dopamine

Question 25

What are most mastitis infections caused by?

Answer 25

Bacteria

*failure in keratin plug and smooth muscle sphincter –> infection in streak canal

Question 26

Signs of mastitis? BW, milk

Answer 26

BW: inc WBC and inflammatory response

Milk: may appear normal in subclinical infections

Question 27

Economic loss and mastitis?

Answer 27

Economic loss is SEVERE