Lactation

Question 1

Problems associated with lactation

Answer 1

Decreased fertility
Compromised immune function
Increased lameness, mastitis
Kexxtone bolus

Question 2

Composition of milk in different species

Answer 2

Cow - 4% fat, 3.2% protein, 4.5% lactose
Human - low protein, high lactose
Rodent - high fat and protein.
Aquatic - high fat, little lactose

Question 3

What are the major proteins found in milk

Answer 3

Caseins

Question 4

What are the whey proteins in milk

Answer 4

• B lactoglobulin
• alpha lactalbumin
• immunoglobulins

Question 5

Why is fat beneficial in milk

Answer 5

Essential for neonatal nutrition and survival

Question 6

Colostrum composition

Answer 6

Immunoglobulins for passive immunity
Gut closure important for absorption
High in fats, proteins, vitamin A
Low in lactose

Question 7

Embryology

Answer 7

Two parallel lines of ventro-lateral ectoderm in embryo
Develop into thickenings known as mammary band/streak/line
Mammary buds grow into underlying mesenchyme

Mammary glands = EPITHELIAL
(distinct developmental pattern)
- compound alveolar glands

Question 8

Anatomy of mammary gland

Answer 8

Teat/nipple and associated ducts
Alveoli
Secretory cells
Supporting tissues.

Question 9

Supranumerary teats

Answer 9

Extra buds may form in development

often removed in dairy heifers

Question 10

What is the gland cistern seperated from the annular fold by

Answer 10

Annular fold

Question 11

What muscle contracts around the teat (streak) canal

Answer 11

Sphincter muscle

Question 12

What is involved in the suspensory system and function

Answer 12

Median suspensory ligamanet
Pre-pubic and sub-pubic ligaments.
ATTACH UDDER TO BODY

Question 13

What is a modification of the sweat gland

Answer 13

Mammary gland

Question 14

Where does the mammary gland arise from

Answer 14

Lateral lines on ventral surface of developing conceptus = mammary ridges

Question 15

Where is milk stored

Answer 15

Alveoli

Question 16

How does the teat canal respond to infection

Answer 16

Cytokine production

Question 17

Anatomy of the alveolus

Answer 17

Basket like arrangement of polarized epithelial secretory cells

Surrounded by contractile
myoepithelial (smooth muscle) cells and blood vessels

Myoepithelial cells contract alveoli and milk
is ejected into ducts

Question 18

What is the secretory cell

Answer 18

Highly metabolically active cell lying on a basement membrane and surrounded by a ‘glue’ of collagenous extracellular matrix

Question 19

What firms the impermeable barrier between secretory cells

Answer 19

Tight junctional complexes

Question 20

Important events in mammogenesis

Answer 20

Isometric growth until puberty

Allometric growth and regression during oestrous cycles

Critical window at puberty; overfeeding detrimental

Start of gestation: extensive duct system lying in fat pad

Secretory cells proliferate during gestation, displacing fat

Some proliferation in early lactation, but mainly differentiation

Gradual involution (apoptosis) during declining lactation

Rapid involution after drying-off or

Question 21

Role of oestrogen in development of mammary gland

Answer 21

Ducts begin to branch and increase in diameter

Question 22

Role of progesterone in development of mammary gland

Answer 22

Terminal portions of branch begin to form alveoli

Question 23

Role of prolactin and GH in development of mammary gland

Answer 23

Increase during onset of puberty and needed for more comp,were and rapid development of ducts.

Question 24

Milk ejection reflex

Answer 24

Teat stimulation causes afferent neural inputs terminating in paraventricular nucleus of hypothalamus

Oxytocin released from posterior pituitary (efferent endocrine arc)

..leading to contraction of myoepithelial cells in mammary gland
Stimulation - secretion delay determines milking routine

Question 25

What is galactopoiesis

Answer 25

Maintenance of established lactation

Question 26

What does continued milking do

Answer 26

Stimulates release of galactopoietic hormones Prevents milk stasis

Question 27

How does milk stasis inhibit secretion

Answer 27

Feedback inhibition Physical disruption

Question 28

What hormone drives lactation

Answer 28

GH

Question 29

Methods of increasing yield

Answer 29

Genetic improvement Nutrition Milking technology Frequent milking Growth hormone Experimental thyroxine and oxytocin

Question 31

What happens after lactation

Answer 31

Apoptosis

Question 32

What is apoptosis inhibited by

Answer 32

Prolactin GH IGF1

Question 33

What is apoptosis stimulated by

Answer 33

Weaning Milk stasis Local increase in IGFBP5

Question 34

What promotes cell survival

Answer 34

Prolactin and GH

Question 35

How does the accumulation of milk lead to cessation

Answer 35

Through lack of galactopoietic hormones Feedback inhibition Pressure and physical disruption Casein hydrolysation

Question 36

Milking machine function

Answer 36

Milk removed by creating negative pressure outside the teat – applying a vacuum (42-48 kpa) controlled by regulator Continuous vacuum would stop circulation in teat. Applied intermittently via pulsator liner opens and closes allowing teat to rest and circulation restored, 60/min Vacuum on to vacuum off 2:1 Claw piece for collecting milk Long milk tube to bulk tank

Question 37

Milking parlour systems

Answer 37

Herringbone Tandem Rapid exit Abreast Rotary