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Y3 MOD Reproductive > Equine Pregnancy > Flashcards

Equine Pregnancy Flashcards

1
Q

How long is the gestation of a mare?

A

336 days

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2
Q

Describe how the length of equine pregnancies can vary

A

“Overdue” foals seldom cause a problem
“Foals come when they are ready – not when they are due”
“The foal determines the day, the mare the hour”

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3
Q

Where does fertilisation occur?

A

In the ampulla of the oviduct

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4
Q

Describe the migration of the embryo

A
  • Embryo remains in oviduct until about day 5-6 when it enters the uterus
  • Embryo migrates around the uterus between up to day 15-16
  • On day 15-16 embryo fixes in position, usually at the base of one horn
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5
Q

What is migration to the uterus essential for?

A

Maternal recognition of pregnancy and prevention of release of PG by endometrium

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6
Q

When does placental attachment begin?

A

Day 36

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7
Q

Describe foetal migration later in pregnancy

A

Foetus grows into uterine body after 70-80 days, found mostly in the body until 6-7 months, after which it is so large it occupies part of the horn again

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8
Q

Maternal recognition of pregnancy prevents?

A

Regression of the primary CL from day 14 onwards

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9
Q

What maintains pregnancy at the start?

A

Progesterone secreted from the CL

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10
Q

What occurs at day 35?

A

Endometrial cups start secreting eCG

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11
Q

What is the function of eCG?

A

Maintains primary CL and encourages secondary CL formation - maintain pregnancy for the first 5 months

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12
Q

The cups are gone by?

A

day 150

- start to degenerate around day 70

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13
Q

How is pregnancy maintained after day 200?

A

Foetal-placental progesterone production

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14
Q

What is produced from day 60 onwards?

A

Foetal gonads produce oestrogens

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15
Q

Describe endometrial cups

A

Come from the mare not the foal
Once in place and producing eCG the cups can only be removed by natural regression
Whilst they are in place the mare will not come into oestrus

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16
Q

Why must aborting a foal occur before day 35?

A

Cups remain even if a foal has died and wont regress until day 100-150
- any attempt to abort foal must be done before day 35 if it is desired to get the mare to breed again in the same breeding season

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17
Q

What are the 4 methods of pregnancy diagnosis?

A

Failure to return to oestrus
Laboratory tests
Manual rectal exam
Ultrasound

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18
Q

Describe using failure to return to oestrus for pregnancy diagnosis

A
  • Particularly at day 14-21 after mating
  • Initial screening test but not definitive
  • Mares may not show oestrus for behavioural reasons
  • Conversely some mares display signs of oestrus during pregnancy
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19
Q

Describe the laboratory tests used for pregnancy diagnosis

A

Blood samples (serum usually):
- eCG: from days 45-90 (from the endometrial cups)
- Oestrone sulphate: from days 120 onwards (produced by the foetus) – also indicates foetal viability
Urine sample: Oestrone sulphate in urine after day 150

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20
Q

Describe manual rectal palpation for pregnancy diagnosis

A
  • Possible by very skilled operators at day 20
  • Usually left until day 40 (six weeks), orange sized lump in the uterine horn
  • By day 120: maybe able to ballot foetus
21
Q

Rectal ultrasound for PD can be done how long after mating?

A

Can be done from about 10 days after mating with care –but not necessarily useful at this time – embryonic death may occur later and twins can be missed

22
Q

What are some points to consider when timing rectal ultrasounds for PD

A
  • Early embryonic death rates are highest in first 14 days
  • In twins: one twin maybe days younger (and therefore smaller) than the other
  • Conceptus motile to day 16 - useful to distinguish cyst from twin and twin from twin.
  • Twins reduction better done when twins smaller
  • After day 30-35 endometrial cup production will prevent the mare returning to oestrus if the pregnancy is terminated.
  • After about 6 weeks can’t image whole foetus – only parts
  • Owners incompetence
23
Q

Describe a common scanning course for PD on professional studs

A
  • First scan 15-16 days post mating: check for pregnancy, check for twins
  • Second scan day 24-26: heartbeat visible, can still reduce twins
  • Third scan – 6 weeks (optional): embryonic death unlikely now
24
Q

When can transabdominal ultrasound be used for PD?

A

From 6 months onwards

25
Q

Describe the names given to pregnancy failure at different points in the pregnancy

A
  • Early embryonic death: from fertilisation to day 40
  • Abortion: from day 40-300
  • Stillbirth: from day 300 onwards
26
Q

Name some example causes of pregnancy failure

A
  • Viral e.g. EHV, EVA
  • Bacteria
  • Twins
  • Foetal abnormalities
  • Maternal illness or stress
  • Idiopathic
27
Q

When does early embryonic death occur?

A

Loss before day 40

28
Q

What are some example causes of early embryonic death

A
  • Congenital/genetic abnormalities.
  • Breeding on foal heat.
  • Uterine environmental problems e.g. endometritis
29
Q

How is early embryonic death diagnosed?

A

Found empty on repeat scan

Abnormal size or shape conceptus seen on scan

30
Q

Name two viral causes of pregnancy failure

A

Equine herpes virus 1

Equine viral arteritis

31
Q

Describe equine herpes virus 1 and how it causes pregnancy failure

A
  • Abortion usually late term (> 5 months) 2 weeks-3 months post infection
  • Often no warning signs
  • Foals maybe born alive but very weak – these quickly die
  • Spread mainly by respiratory route but aborted foetus, membranes and vaginal discharges highly contagious
32
Q

How is equine herpes virus 1 diagnosed?

A

Nasopharyngeal swabs for horses showing respiratory signs -PCR
Submission of aborted material -PCR

33
Q

How is equine herpes virus 1 treated?

A

None for individual cases.
Isolate and disinfect
Separate pregnant mares from young stock – who are most likely to be clinically affected.

34
Q

Can equine herpes virus be prevented?

A

Vaccination in 5, 7and 9 month of pregnancy may reduce risk of disease but does not give full immunity

35
Q

Describe equine viral arteritis and how it causes pregnancy failure

A
  • Notifiable in UK in Stallions and mares mated in last 14 days
  • Infected stallions become persistently infected shedders
  • Infected mares abort then recover
36
Q

Can equine viral arteritis be prevented?

A

Vaccine available – make sure animal tests seronegative for EVA before vaccination.

37
Q

Name and describe bacterial causes of abortion

A
  • Often Strep. spp. Also E.coli, and Staph. spp
  • Ascending infection from cervix
  • Haematogenous spread
  • Introduction of bacteria at breeding
  • Antibiotics/Nsaids – but often too late
38
Q

Describe twins in the womb and how it leads to low survival

A

Twins compete with one another for attachment space (= nutrition) –often one twin will run out of space early in pregnancy and die off. The other twin will carry on growing until, it too, is deprived of space by the remnants of the dead twin and is aborted

39
Q

Which kind of twin pregnancy is more likely to have surviving foals

A

Twins that fix in one horn (unilateral) are more likely to end up with one surviving to term as one twin may die early on whilst it is still very small. (75% self-resolve)

40
Q

Why are bilateral horn twins more likely to both die?

A

Twins that fix in opposite horns (bilateral) are more likely to both abort as they will both get to a reasonable size before they begin to compete with each other.

41
Q

Twin pregnancies have a what % survival rate of a live foal?

A

63

42
Q

How does twin abortion most commonly occur?

A

The pregnancy is aborted, or more usually one twin is manually “reduced” or crushed (by a vet)

43
Q

Describe the steps in reducing a twin pregnancy

A
  • The rectum must be relaxed so the use of sedatives and hyoscine maybe helpful or necessary.
  • NSAID injection is used to prevent induced inflammation affecting the other foetus
  • The mare must be scanned again in 24-48 hours to ensure reduction was successful (not all reduced twins are felt to “pop” – some just need damaging for successful reduction)
44
Q

What are some signs of abortion?

A
  • Maybe none!
  • Mare often perfectly well in herself.
  • If mare off colour – maybe cause of abortion, not due to abortion e.g. viral infection
  • Vaginal discharge
  • Running milk – lost colostrum before foaling
  • Colic/foaling signs
45
Q

What samples can be sent to investigate abortion?

A
  • Send whole carcass and placenta to pathologist
    If not possible:
  • Exam placenta and cord
  • External exam of foal -weight, crown-rump length
  • Internal exam –signs obvious problems
  • Sample chorion, thymus, liver, lung, spleen, fresh and fixed – can be tested for EHV plus bacterial culture, and histopathology
46
Q

How can you induce abortion before 3 months?

A

Prostaglandin injection should – abortion 5-8 days afterward

If endometrial cups present – mare will not return to oestrus this breeding season

47
Q

How can you induce abortion after 3 months?

A
  • Repeated prostaglandin injections
  • Dilation of cervix and uterine lavage.
  • Transabdominal injection of potassium chloride into foetal heart?
  • Considerable risk in attempting termination of pregnancies after 100 days
48
Q

How can foaling be induced?

A

Inject 10-20iu oxytocin (1-2ml) every 15-20min until delivery starts (may only need one dose).
Risky procedure, for this to work well, mare must basically be about to foal anyway

49
Q

What are the risks of inducing foaling?

A
  • Uterine rupture
  • Dystocia
  • Foal immaturity (matures in last 1% of pregnancy)
  • Retained membranes

Y3 MOD Reproductive (11 decks)

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