Lactation

Question 1

During foetal development and pregnancy, what happens to the dam?

Answer 1

Mammogenesis

Question 2

Before, during and after parturition, what takes place?

Answer 2

Lactogenesis

Question 3

After parturition an during neonatal development, what takes place?

Answer 3

Galactopoiesis

Question 4

What is the predominant dairy herd (UK)? What is the UK average yield?

Answer 4

Holstein

Question 5

What is the average milk composition (fat, protein and lactose)

Answer 5

4% fat

3. 2% protein
4. 5% lactose

Question 6

How has milk yield increased over the decades

Answer 6

Improved genetics (AI)
Improved nutrition
Improved technology

Question 7

What problems are associated with lactation? (most problems are early lactation)

Answer 7

Decreased fertility
Metabolic stress
Compromised immune function 
Mastitis 
Increased lameness

Question 8

What is the majority of milk proteins?

Answer 8

Caseins

Question 9

Apart from caseins, whey proteins are also in milk. What do they include?

Answer 9

B lactoglobulin
A lactalbumin
Immunoglobulins

Question 10

Why might variation in milk composition occur?

Answer 10

Between breeds
Between species
Across lactation and milking 
Nutrition 
With seasons

Question 11

How is colostrum formed?

Answer 11

Pre-partum milk secretions that is not removed –> colostrum

Question 12

Does colostrum provide passive or active immunity? Where are the immunoglobulins produced?

Answer 12

Passive

By plasma cells in the mammary gland

Question 13

Describe the composition of colostrum in terms of fat, proteins, vitamins and lactose

Answer 13

High fat
High protein
High vit A
Low lactose

Question 14

How long is colostrum secreted for? How long is milk withheld from human consumption?

Answer 14

Several days

4 days

Question 15

Mammary glands form from which germ layers?

Answer 15

Ectoderm
Develop into mammary band
Mammary buds grow into underlying mesenchyme

Question 16

What type of glands are mammary glands (simple, compound, alveolar, tubular, alveolar)?

Answer 16

Compound alveolar

Question 17

What is the name of extra mammary buds formed during development? (Often removed in dairy heifers)

Answer 17

Supranumery teats

Question 18

What separates the teat cistern from the glandular cistern?

Answer 18

Annular fold

Question 19

What is present around the teat (streak canal)?

Answer 19

Sphincter muscle

Question 20

What attaches the udder to the body? What does this consist of?

Answer 20

Suspensory system (4 ligaments):
Median, lateral, pre- pubic and sub-pubic ligaments

Question 21

The gross anatomy of the udder is separated into…

Answer 21

Rear and fore quarters (attached to body via rear/fore quarter attachment)
Mammary groove running between L and R teats

Question 22

What is the name of the secretory tissue in mammary glands?

Answer 22

Parenchyma

Question 23

What is the name of the ducts and storage sinus within a fat pad of the udder? What happens here?

Answer 23

Cistern

udder cistern and teat cistern

Question 24

Ducts move milk from where to where?

Answer 24

Alveoli to teat

No internal crossover

Question 25

Where is miked stored between milking?

Answer 25

Some in cisterns | Most in alveoli

Question 26

How does the teat canal respond to infection?

Answer 26

Cytokine production

Question 27

The alveoli consists of what cell arrangement?

Answer 27

Polarised, epithelial secretory cells

Question 28

What surrounds the alveoli?

Answer 28

``` Myoepithelial cells (smooth muscle) Blood vessels ```

Question 29

How is milk ejected from alveoli into ducts?

Answer 29

Contraction of myoepithelial cells

Question 30

What are the secretory cells? From which surface is milk synthesised?

Answer 30

Cells on basement membrane surrounded by collagenous extracellular matrix Apical surface

Question 31

What is the prime determinant of milk yield?

Answer 31

Number of secretory cells

Question 32

What happens to the cells in the udder during pregnancy and early lactation?

Answer 32

Proliferation of secretory cells displace fat pads | Mainly differentiation in early lactation

Question 33

Describe growth of the mammary tissue during puberty and during oestrus cycles

Answer 33

Puberty = isometric growth (grows in proportion to rest of body) Oestrus cycle = allometric growth (grows at different rate to rest of organs) and regression

Question 34

What happens to the cells of the udder during declining lactation?

Answer 34

Apoptosis | And involution

Question 35

Which hormones cause duct growth?

Answer 35

Oestrogen Growth hormone Adrenal steroids

Question 36

Which hormones cause lobulo-alveolar growth?

Answer 36

``` Oestrogen Growth hormone Adrenal steroids Prolactin Progesterone ```

Question 37

Which hormones cause milk secretion?

Answer 37

Prolactin | Adrenal steroids

Question 38

What are the phases that take place to cause milk secretion?

Answer 38

Atrophic ducts Duct growth Lobulo-alveolar growth Milk secretion

Question 39

Which hormones are important in the control go bovine mammary cell proliferation?

Answer 39

Placental lactose Growth hormone (NOT PROLACTIN)

Question 40

What are the 2 stages of lactogenesis?

Answer 40

Acquisition of secretory capability pre-partum | Onset of copious secretion at parturition

Question 41

What hormone is the main requirement for lactogenesis?

Answer 41

Progesterone withdrawal

Question 42

How is milk ejected from the gland?

Answer 42

Teat stimulation causes neuro-endocrine reflex Oxytocin released from posterior pituitary Myoepithelial cells in mammary gland contract Positive pressure in the udder causes milk to be pushed out

Question 43

Describe a basic milking routine

Answer 43

Clean (predip/wipe) udders Identify animal Inspect for clots Leave 30-45 seconds for oxytocin release and action Cluster on then removed Teat dip applied post milking Loafing time to allow teat sphincter to close

Question 44

What is galactopoeisis?

Answer 44

Maintenance of established lactation

Question 45

What does continued milking do to allow galactopoiesis?

Answer 45

Prevents milk stasis | Stimulates the release of galactopoiesis hormones

Question 46

How does milk stasis inhibit milk secretion? (2 ways)

Answer 46

``` Feedback inhibition (within hours) Physical disruption (within days) ```

Question 47

In most species, what hormone drives lactation? Which species is the exception and what hormone drives their lactation?

Answer 47

Most species = prolactin | Cows = growth hormone

Question 48

A 3 quarted cow reduces yield by what percentage?

Answer 48

10% (not 25%)

Question 49

How can milking yield be increased?

Answer 49

Recombinant bovine somatotropin (rBST) Genetic improvement Nutrition Frequent milking

Question 50

Is BST legal in the EU? Why?

Answer 50

No Burnt out after one lactation and replaced Causes lameness and painful injection abscesses

Question 51

How does bovine somatotropin cause an increased milk yield?

Answer 51

Redirects nutrients towards the other

Question 52

Give one way that milk production can be inhibited to match supply to demand

Answer 52

Feedback inhibitor of lactation (FIL - autocrine peptide) | Negative feedback

Question 53

Large cistern cows produce more milk per gram of secretory tissue. Do large cistern cows tolerate frequent or infrequent milking better?

Answer 53

Tolerate infrequent milking | Respond less well to frequent milking

Question 54

After peak lactation, what causes milk yield to decrease?

Answer 54

Decreased number of secretory cells by apoptosis | Due to FIL and lack of gelactopoietic hormones

Question 55

What stimulates apoptosis of secretory cells?

Answer 55

Weaning Milk stasis Local increase in IGFBP5

Question 56

What inhibits apoptosis in secretory cells?

Answer 56

Prolactin Growth hormone IGF1

Question 57

What are the types of milking parlour?

Answer 57

``` Abreast Tandem Herring bone Rapid exit Rotary Robot ```

Question 58

How milking clusters cause milking?

Answer 58

Vacuum creates negative pressure outside the teat Pushes milk out Vacuum on:off 2:2