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A - Equine Repro > Oestrus cycle manipulation and AI > Flashcards

Oestrus cycle manipulation and AI Flashcards

1
Q

What is the cycle length of a mare?

A

21 days

-Heat for 7 days

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2
Q

In order for TB’s to foal down as close as possible to August 1st, when should they be bred?

A

September-October

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3
Q

What are 5 methods to induce oestrus in mares not undergoing oestrus cycles?

A 
Artificial lighting
Dopamine antagonists
GnRH
Progestins
Combination of methods
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4
Q

If using artificial lighting to induce oestrus, what are the two different methods for doing so?

A

Gradual increase
-Extra 30min/week up to 14/16 hours a day
Intermittent
-1 hour of light during night

*note do not give more than 16 hours of light/day as it will delay oestrus

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5
Q

How far prior should you start artifical light therapy before breeding date?

A

60 days at least

Therefore start July 1st to by cycling by mid August/September

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6
Q

What is mechanism of action of dopamine antagonists?

A

Increase prolactin secretion
-Increase prolactin, increase LH receptors on ovary, increases sensitivity to low conc. of LH which is present during anoestrus

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7
Q

What are the 2 types of dopamine antagonists that are used?

A

Sulpiride IM BID max 21 days

Domperidone oral SID max 55 days

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8
Q

Define a treatment strategy timeline for an anoestrus mare using artifical light and a dopamine antagonist?

A

Day 0 Begin light supplementation
Day 14 Scan for mares with follicles at least 15mm
Commence daily treatment with domperidone
Day 22-30+ Induce ovulation when follicles are at least 35 mm

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9
Q

What is the problem with using GnRH to induce oestrus?

A

GnRH is released in the body in pulses and therefore can’t just simply give a daily injection

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10
Q

When do you get the best response to induce early oestrus onset by using progestins?

A

Late transition period with follicles at least 25mm

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11
Q

How long should you use progestins for to induce early onset of oestrus?

A

10 to 15 days
Takes 4-7 days to oestrus
Takes 7-12 days to ovulation

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12
Q

What are 3 methods of progestin administration?

A

Altrenogest orally daily
Progesterone IM daily
IM prolonged release microspheres
Intravaginal admin Cue-Mare

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13
Q

When should you try and induce ovulation in a late transitional mare?

A

Follicle at least 35mm
Evidence of oestrual behaviour
Oedema in uterus

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14
Q

What are 2 methods to induce ovulation in a late transitional mare?

A

hCG

Deslorelin

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15
Q

What do you need to warn the owner about when trying to induce ovulation in a late transitional mare?

A

That an ovulatory sized follicle may or may not ovulate still - anovulation
Better to first confirm she has ovulated at least once before managing breeding

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16
Q

What are 3 indication for synchronisation of oestrus in cycling mares?

A

Embryo transfer program
Synchronise mares for breeding with stallion
Synchronise ovulation for breeding with frozen or cooled shipped semen

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17
Q

What are the 4 broad methods to synchronise oestrus and/or ovulation in cycling mares?

A

Termination of luteal phase
Lengthening of luteal phase
Induction of ovulation
Inhibition of follicular development

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18
Q

What class of drugs do you use to terminate the luteal phase?

A

Prostaglandins

-PGF2alpha or synthetic analogues

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19
Q

What are 2 drugs that are used to terminate the luteal phase in mares?

A

Dinoprost

Cloprostenol

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20
Q

What do you need to remember when terminating the luteal phase in regards to effectiveness?

A

That the corpus luteum is only responsive after 5 days postovulation

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21
Q

After giving a prostaglandin to terminate the luteal phase, what is the interval to oestrus and ovulation?

A

Interval to oestrus - 2-7 days if in presence of mature CL

Interval to ovulation- 9-11 days

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22
Q

What things make up the variability of effectiveness to terminate the luteal phase by injecting prostaglandins?

A

Stage of follicular development
If a mature CL present
Cycling status at time of treatment
-Anoestrus or not

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23
Q

In a herd of randomly cycling mares, what dose regime can you employ to terminate the luteal phase by using prostaglandin?

A

Giving 2 doses 14 days apart

You will get the majority of the mares to sync-up

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24
Q

How can you lengthen the luteal phase in a mare?

A

By giving exogenous progestins for 10-15 days

-(Average life of CL is 14 days)

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25
Q

When lengthening the luteal phase by giving progestins, what may you need to incorporate if treating for over 15 days?

A

Prostaglandin to induce luteolysis

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26
Q

Describe the timeline of a treatment protocol using a cue-mare to lengthen the luteal phase?

A

Day 0 Insert cue-mare
Day 7 Scan and remove if follicle over 35mm
Day 10 Scan and remove cue-mare, +/- PG injection
Day 11+ Normal breeding protocol

27
Q

What is the principle behind how to successfully induce ovulation?

A

Either induce or mimic the preovulatory LH surge in the presence of a follicle that is mature enough to respond by ovulating

28
Q

What are the 2 drugs that are used to induce ovulation, and what are their effects?

A

hCG
-LH like effects
Deslorelin acetate
-GnRH agonist

29
Q

How long after injection with hCG do mares typically ovulate?

A

36 +/- 17 hours

30
Q

How long after injection/implantation with deslorelin acetate do mares typically ovulate?

A

38 hours (32-48)

31
Q

When using frozen semen in a mare, when should you AI her in regards to ovulation?

A

AI 12 hours before

or 6 hours after

32
Q

What is foal heat?

A

The first heat period after parturition

33
Q

When do pregnancy rates increase after parturition?

A

After day 15

-Related to degree of involution of the uterus when embryo reaches it

34
Q

What are the 2 methods used to improve fertility around foal heat?

A

Delay ovulation
-Administer altrenogest from day of foaling and inject PGF2alpha on day 9
Skip foal heat
-Allow mare to ovulate and administer PGF2alpha 5-6 days post ovulation to “short-cycle” the mare and induce oestrus

35
Q

What are the 4 main categories to suppress oestrus in a mare?

A

Hormonal - Progestins
Surgical - Remove ovaries
Immunological - Anti-GnRH vaccine
Other - Abortion, glass marbles insertion

36
Q

In a mare where the owners may want to breed from her in the future, but presently want to suppress oestrus, what method would you recommend?

A

Giving progestins

37
Q

Quickly list some advantages of AI in mares

A

Genetic access to wider range of stallions
Disease control and reduce contamination
Safety
More optimal use of subfertile stallions
Minimal contamination breeding techniques
Don’t need to transport mare or stallion

38
Q

What is the conception rate of AI compared to natural service when using fresh/chilled semen?

A

Same or slightly improved in some mares

39
Q

What are the preferred timeframes for using fresh, chilled and frozen semen?

A

Fresh 0-6 hours
Chilled 12-72 hours
Frozen Over 72hours

40
Q

What temperature should semen be stored at if chilled or frozen?

A

Chilled 4-8 degrees

Frozen -196 degrees

41
Q

What breed can you not use AI on?

A

Thoroughbreds

42
Q

What temperature should an AV be?

A

42-48 degrees

43
Q

What are the 4 methods to collect semen from a stallion?

A

Phantom
Oestrous mare/treated mare
Standing collection
Chemical ejaculation

44
Q

What are the 4 components that make up a semen extender?

A 
Buffers
Energy
Proteins
Usually antibiotics 
-Are skim milk or yolk based
45
Q

What are the 3 purposes that semen extenders serve?

A

Provide energy for metabolism
Stabilise cell membranes
Reduce bacterial contamination

46
Q

Immediately after collection how much extender should you put in with the semen?

A

1: 1 to 1:3 extender

- Make sure to prewarm extender

47
Q

What 5 things can you do to troubleshoot poor longevity of semen after extension?

A

Do BSE and check morphology and motility before processing
Use of a different extender
Change dilution ratio
Centrifuge and remove excess seminal plasma
Collect only sperm rich fraction during ejaculation

48
Q

Describe the critical values for cooling semen?

A

37-20 degrees rapid cooling
20-5 degrees cool at 0.5-1.0 degree/minute
4-6 degrees maintain temperature ag

49
Q

Describe a breeding strategy with cooled semen?

A 
Open and check record - correct stallion
Mix semen
Aspirate into syringe and note volume
Check that correct mare
Check for correct stage of cycle
Inseminate into body of uterus
50
Q

What is the lifespan of semen in a mare when it is fresh and frozen?

A

Fresh up to 5 days

Frozen up to 24 hours

51
Q

What are some limitations of frozen semen?

A 
Shorter lifespan
Reduction in semen quality
Lower conception rates
May require more services
Some uterine inflammation can occur
Need intensive management of mare
52
Q

For frozen semen what quality do they need to be and how much is in a dose?

A

Minimum quality 30% progressively motile
50% normal sperm
Dose is 300 million progressively motile sperm

53
Q

Describe the process of freezing semen, from collection?

A 
Collect and evaluate
Extend in centrifugation media 
Centrifuge
Remove supernatant
Re-suspend in freezing suspender 
Freeze
54
Q

How should you thaw frozen semen?

A

Check with specific instructions supplied with the straw

0.25-0.50mL 37 degrees for 30 seconds in water bath

55
Q

What makes up the mare selection criteria for using AI by frozen semen?

A 
Preferably young
Good conformation
No history of infertility
BSE inc. uterine biopsy and culture, free of infection or treated 
Cycling with regular oestrous cycles
Don't use transitional mares
56
Q

What are the 3 most common strategies for AI with frozen semen?

A

Timed AI double insemination
-scan and inject with hCG/deslorelin once follicle over 35mm, inseminate at 24 and 40 hours post-injection
Timed AI single insemination
-Same but scan 24hr after injection and assess, or inseminate 32-34 hours after injection
AI within 6 hour post ovulation
-most common
-Same but scan every 6 hours and AI when ovulated

57
Q

Describe the AI technique for frozen semen in the mare?

A

Thaw straw as per instructions
Load pipette
Deposit into body of uterus or deep intrauterine AI ipsilateral to ovulatory follicle
Infuse air through pipette to empty all contents
Infuse 4-6ml of extender
Re-examine mare 12+ hours post ovulation to confirm ovulation and detect inflammatory fluid

58
Q

If inflammatory fluid is detected post AI, what 4 treatments can you consider using?

A

Uterine lavage
Oxytocin treatment
Antibiotics
Caslicks

59
Q

What benefits does endoscopic insemination have when using AI?

A

Dose can be deposited under visual control at utero-tubal junction
Allows increased conception rates when using smaller doses of sperm
Insemination doses can be under 5 million, or if sex sorted sperm are used

60
Q

List some advantages of using embryo transfer?

A

Can breed at earlier age
Offspring from endangered animals
Get pregnancies from mares still in competition or who foal late in the breeding season
Removes risks associated with foaling in valuable mares
Improves genetic gains

61
Q

List some disadvantages of using embryo transfer?

A

Cost $2,000 - $4,000
Superstimulatory treatments less successful
Expertise
Need a group of fertile recipient mares

62
Q

Describe the process of embryo transfer in mares?

A

Sync ovulation of donor and recipient mares
Breed donor mare
Day 6-8 post-ovulation flush uterus of donor mare to retrieve embryo
Wash and evaluate embryo
Load into transfer straw
Transfer to uterus of recipient

63
Q

When doing embryo transfer to the recipient mare, why do you need to ensure everything is done aseptically?

A

They will be in dioestrous

-Therefore cervix will be closed and will be more prone to infection

64
Q

When choosing a recipient mare, can you use on that has been ovariectomised or is anovulatory?

A

Yes but treat with progesterone or progestins 4-7 days prior to transfer, and continue treatment for 100-140 days

A - Equine Repro (4 decks)

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