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
How much do follicles grow roughly a day (LA)?
3-5mm
26
What size and shape of a follicle indicate ovulation?
>35mm diameter Tear drop shape Thickened wall
27
How long is the mare cycle? How long is oestrus? When does ovulation occur?
21 days Oestrus for 7 days Ovulation 24-48hrs before oestrus ends
28
Why might oestrus be manipulated?
Synchronisation Easier oestrus detection Enable AI and ET Trigger post-partum resumption
29
With oestrus manipulation, what are we aiming to control?
Corpus luteum influence and follicular waves
30
What hormone should be given to shorten the luteal phase?
PGF2a
31
What hormone should be given to extend the luteal phase?
Progesterone
32
For fixed time AI in heifers, what hormone should be given twice? (11 days apart)
PGF2a
33
How can exogenous progesterone be given to sheep/cattle?
Intra-vaginal progesterone device/progesterone releasing uterine device (PRID) Progesterone sponge
34
What hormone might be given to cattle with insertion of an intra-vaginal progesterone device?
GnRH
35
How long do sheep have a progesterone sponge in for?
9-19 days
36
What are causes of anoestrus?
``` Pregnancy Lactation Stress Season Negative energy balance Pathology ```
37
What is the suckling effect in beef cows?
More suckling --> low frequency of LH pulses | Less suckling --> dramatic increase in LH pulses
38
How does the insertion and removal of a progesterone releasing intra uterine device alter GnRH?
Inserting PRID - GnRH suppression | Removing PRID - GnRH surge
39
How can puberty be induced in sows?
PMSG | hCG
40
How can oestrus be synced in sows?
Progesterone
41
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?
Fresh - 72 hrs Chilled - 24hrs Frozen - 12 hrs Ovum life shorter