Repro 3

Question 1

List the vet definitions of puberty and what this means for male and female

Answer 1

Puberty = the acquisition of reproductive competence
MALE:
1. Age when ejaculate contains sufficient spermatozoa to fertilise
FEMALE:
1. Age where female can support a pregnancy without deleterious effects (successful preg and own growth not inhibited)

Question 2

How does lactation affect cycling?

Answer 2

1. L inhibits GnRH pulse generator
2. Plasma FSH sufficient to allow follicle development BUT GnRH pulsatility is too low to allow ovulation
3. Suckling frequency increases inhibition

Question 3

Is a dairy or beef more likely to come into oestrus sooner and why?

Answer 3

1. Dairy

2. Milked on average 2X a day vs beef milked at higher frequency

Question 4

How does seasonality affect cycling?

Answer 4

1. seasonality is controlled by GnRH pulse generator
2. in spring = decreased melatonin which has a different affect on different species: sheep = suppresses pulsitility. Horses = increases

Question 5

Normal physiological reasons when GnRH pulsatility is suppressed and ovarian cycles stop:

Answer 5

1. Lactation
2. Photoperiod - (day length) seasonality
3. Pregnancy
   once animal starts = continues forever

Question 6

Pathological inputs (physical or mental) to the GnRH pulse generator in animal. Especially what type of animal and why?

Answer 6

Type = newly calved dairy heifer as is a Metabolic athlete and:

2. Stress, being bullied (introduced to herd),
3. Weight loss (lactating),
4. Lactating,
5. Growing

Question 7

Why can’t you throw hormones at a newly calved dairy heifer that isn’t coming into oestrus?

Answer 7

1. not respond to drugs

2. cause of hypothalamus not firing

Question 8

List the physiological and pathological reasons for decrease in GnRH pulse frequency

Answer 8

Physiological:
1. Lactation
2. Pregnancy
3. Day length (photoperiod)
Pathological reasons
1. Starvation
2. Stress
3. Disease

Question 9

Why can’t you throw hormones at a newly calved dairy heifer that isn’t coming into oestrus? What do you have to do instead?

Answer 9

1. not respond to drugs
2. cause of hypothalamus not firing
3. have to sort the underlying problem: think “why not coming into oestrus?” bullied = stress? starving? disease?

Question 10

Outline structure of mammary gland

Answer 10

1. it is a modified sweat gland. Ectoderm epithelial cells

2. Species specific as to how it develops

Question 11

How does mammary gland develop

Answer 11

1. Modified sweat gland
2. starts as mammary ridge: ectoderm cells
3. starts to bud: species specific = diff number of glands, location and structure of teat
4. Arise from lateral lines on ventral abdomen
5. diff number of glands

Question 12

Outline structure of mammary gland

Answer 12

1. Highly organised and vascularised structure external to body cavity
2. parenchyma = secretary tissue
3. Milk duct connects to many alveoli which grow into lobules at lactation
4. alveoli = like bunch of grapes

Question 13

How does mammary gland develop

Answer 13

1. Modified sweat gland
2. starts as mammary ridge: ectoderm cells
3. starts to bud: species specific = diff number of glands, location and structure of teat
4. Arise from lateral lines on ventral abdomen
5. Primary buds, then secondary.
6. Buds then canalised (tube in them)
7. most development after puberty

Question 14

Comparative microanatomy of diff species

Answer 14

1. Ruminants = 1 canal
2. Horse and pig = 2-3 ducts to canal
3. dogs and cats = multiple canals

Question 15

What specialises the mammary epithelial cells of alveoli?

Answer 15

1. Highly metabolically active cells on a basement membrane surrounded by collagenous extracellular matrix
2. loads of rough ER, golgi, smooth ER
3. milk synthesides across apical surface

Question 16

What is the major composition of milk

Answer 16

1. protein, fat, lactose

2. differs between sepcies

Question 17

What is the ion composition of milk

Answer 17

Na+, K+, Cl-, Ca2+

Question 18

Colostrum

Answer 18

1. prepartum milk secretion
2. Immunoglobulins produced by plasma cells in gland = passive immunity
   3, short window for absorption
3. high in fats, proteins, Vit A, low in lactose

Question 19

What is lactogenesis and galactopoesis

Answer 19

1. L = onset of milk secretion

2. GP = continuation of lactation

Question 20

What are the 2 stages of lactogenesis?

Answer 20

Stage 1: acquisition of secretory capability PRE PARTURITION
Stage 2: onset of copious secretion at/ around parturition

Question 21

What ensures the synchrony between stage 2 and partuition?

Answer 21

HORMONES

1. inc cortisol (stress) (adrenal gland)
2. inc prolactin (anterior pituitary)
3. Inc oestrogen
4. progesterone plummits = signal of end of gestation

Question 22

What happens when progesterone decreases at teh end of pregnancy?

Answer 22

1. P affects receptors on milk producing cells to prolactin
2. Prolactin binds
3. allows synthesis of milk

Question 23

How is milk secretion maintained and what is its name?

Answer 23

1. Galactopoesis
2. requires hormones:
   a) prolactin = maintain alveolar cell metabolism
   b) oxytocin = remove milk
   c) GH, insulin, thyroid and cortisol all required indirectly

Question 24

How is milk secretion maintained and what is its name?

Answer 24

Galactopoesis

1. requires hormones:
   a) prolactin = maintain alveolar cell metabolism
   b) oxytocin = remove milk from mammory gland + stimulate myoepithelial cells = muscle cells that sit around alveoli
   c) GH, insulin, thyroid and cortisol all required indirectly
2. REQUIRED removal of milk: feedback inhibitor builds up if not removed

Question 25

Factors that affect milk yield

Answer 25

1. Number of secretory cells in mammary gland 2. blood supply to mammary gland 3. Lactose = most important thing affecting volume. 4. milk removal: suckling/ milking frequency 5. water intake

Question 26

If an animal has low blood glucose what would happen to the milk produced and why?

Answer 26

1. VOLUME would fall 2. glucose is substrate for lactose 3. fall blood glucose = fall in lactose, amount of milk produced = fall

Question 27

How is milk secreted?

Answer 27

1. pushed out by myo epithelial cells (muslce cells) that sit around alveoli 2. mammary epithelial cells of the alveoli secrete milk into alveolar lumen

Question 28

How does neonate get milk out is there is such a big resistance to flow due to small diameter network

Answer 28

1. stimulates milk ejection reflex in mum | 2. Milk PUSHED!

Question 29

Milk ejection

Answer 29

1. Receptors around udder 2. Brain important: smell and sound 3. afferent to spinal chord = brain, hypothalamus, posterior pituitary = releases oxytosin in blood = bind to receptors in myoepithalial cells. 4. neuroendocrine reflex