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repro husbandry > Oestrus and ovulation manipulation > Flashcards

Oestrus and ovulation manipulation Flashcards

1
Q

What is the HPO axis?

A

Hypothalamus produces GnRH which acts on
Anterior pituitary which produce LH and FSH
Which act on ovary to produce progesterone, inhibin and estradiol

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2
Q

What does oestradiol increase in the endometrium?

A

Oxytocin receptors

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3
Q

Where is oxytocin produced? What does it cause the release of?

A

Corps luteum

Release of PGF2a from endometrium

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4
Q

Where is progesterone produced? Which hormones does it suppress and what does this prevent?

A

Corpus luteum

FSH and LH - prevents ovulation

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5
Q

What happens to follicles as progesterone concentrations fall?

A

Follicles develop and secrete oestradiol

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6
Q

What does the dominant follicle secrete? What is the result of this?

A

Inhibin

Suppresses FSH - FSH surge not as strong as LH one

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7
Q

What are the 5 phases of the oestrus cycle?

A 
Pro-oestrus
Oestrus
Metoestrus
Dioestrus
Anoestrus
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8
Q

When does pro-oestrus take place? What does it cause?

A

Immediately before oestrus

Increase in activity - follicular growth, regression of CL from previous cycle

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9
Q

Describe pro-oestrus vaginal mucus

A

Hyperaemic

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10
Q

Describe the histology of a pro-oestrus smear

A

Cornified cells

Large cytoplasm

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11
Q

What is oestrus?

A

Period where female will accept male for copulation

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12
Q

In which phase of the oestrus cycle does ovulation occur? Which species is the exception?

A

Oestrus

Cows - ovulate 12 hrs after end of oestrus

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13
Q

What is the phase after oestrus? What happens?

A

Metoestrus

Oestrogen and progesterone levels low - reduced secretions from uterine, cervical and vaginal glands

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14
Q

What is the phase after met oestrus and what happens?

A

Dioestrus

Corpus luteum are functional and secrete large amounts of progesterone

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15
Q

Which is the longest phase of the oestrus cycle?

A

Dioestrus

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16
Q

What happens during anoestrus?

A 
Quiescence
Minimal follicle development
CL regressed and non-functional 
Lack of FSH and LH 
Lack of ovarian response
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17
Q

Describe the cytology of a smear taken during anoestrus?

A

Parabasal cells

Rounded cytoplasm with round nucleus

18
Q

Describe the cytology of a smear taken during oestrus

A

Complete cornification

Cells with no nucleus

19
Q

How many waves are usually in a cycle? Which species is the exception?

A

3 wave cycle

Cows have 2 wave cycle

20
Q

What is meant by a wave in a cycle?

A

Follicle development before luteolysis

21
Q

How long is oestrus behaviour in cows?

A

9-14 hours

22
Q

Heat detection rate is low in cattle (60-80%) and there is a low heat detection accuracy. Why is this?

A

Unaware of signs
Cows occupied
After midnight
Less than half animals show behaviour of standing to be mounted

23
Q

How can you detect when a cow is in oestrus?

A 
Riding marks on hide
Bulling string - thick mucus form vulva
Tail paint
Mount indicator
Pedometer
24
Q

What should be observed when examining follicles?

A 
Shape
Size
Softness
Wall thickness
Oedema
25
Q

How much do follicles grow roughly a day (LA)?

A

3-5mm

26
Q

What size and shape of a follicle indicate ovulation?

A

> 35mm diameter
Tear drop shape
Thickened wall

27
Q

How long is the mare cycle? How long is oestrus? When does ovulation occur?

A

21 days
Oestrus for 7 days
Ovulation 24-48hrs before oestrus ends

28
Q

Why might oestrus be manipulated?

A

Synchronisation
Easier oestrus detection
Enable AI and ET
Trigger post-partum resumption

29
Q

With oestrus manipulation, what are we aiming to control?

A

Corpus luteum influence and follicular waves

30
Q

What hormone should be given to shorten the luteal phase?

A

PGF2a

31
Q

What hormone should be given to extend the luteal phase?

A

Progesterone

32
Q

For fixed time AI in heifers, what hormone should be given twice? (11 days apart)

A

PGF2a

33
Q

How can exogenous progesterone be given to sheep/cattle?

A

Intra-vaginal progesterone device/progesterone releasing uterine device (PRID)
Progesterone sponge

34
Q

What hormone might be given to cattle with insertion of an intra-vaginal progesterone device?

A

GnRH

35
Q

How long do sheep have a progesterone sponge in for?

A

9-19 days

36
Q

What are causes of anoestrus?

A 
Pregnancy
Lactation 
Stress
Season
Negative energy balance
Pathology
37
Q

What is the suckling effect in beef cows?

A

More suckling –> low frequency of LH pulses

Less suckling –> dramatic increase in LH pulses

38
Q

How does the insertion and removal of a progesterone releasing intra uterine device alter GnRH?

A

Inserting PRID - GnRH suppression

Removing PRID - GnRH surge

39
Q

How can puberty be induced in sows?

A

PMSG

hCG

40
Q

How can oestrus be synced in sows?

A

Progesterone

41
Q

For AI in a mare, how long is the lifespan of semen if fresh, chilled or frozen? How long is the viable life of an ovum in comparison?

A

Fresh - 72 hrs
Chilled - 24hrs
Frozen - 12 hrs

Ovum life shorter

repro husbandry (11 decks)

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