Equine Pregnancy

Question 1

How long is an equine pregnancy?

Answer 1

336days from mating

Question 2

Where does fertilisation occur in the mare? + Movement / attachment?

Answer 2

*Ampulla of oviduct
*Embryo remains in oviduct for 5-6 days when it enters uterus
*Then migrates around uterus up to day 15-16 - movement essential for maternal recognition of pregnancy + prevent= PG release
*On day 15-16 embryo fixed to base of horn + placental attachment post 36days
*Grows in uterine body after 70-80 days -for 6-7months then so big that it occupies part of horn

Question 3

When does maternal recongniton of pregnancy occur?

Answer 3

• 14 days
• CL produces progesterone
• Endometrial cups secrete eCG from day 35 which maintains primary CL + 2ndary CL formation
  *After day 200 CLs degraded + pregnancy maintained by foetal-placental progesterone

Question 4

What are the problems with endometrial cups?

Answer 4

*Once in place will not regress for 100-150days
*If foal has died - mare will not come into oestrus
*Abortion must be done before day 35

Question 5

How can you diagnose pregnancy?

Answer 5

1. Failure to return to oestrus
2. Laboratory tests
3. Manual rectal exam
4. Ultrasound

Question 6

What does failure to return to oestrus say? When?

Answer 6

Failure to return to oestrus
* 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

Question 7

What lab tests could be done? from when?

Answer 7

*eCG - from day 45-90
*Oestrone sulphate from day 120
*Urine sample from day 150

Question 8

How is manual rectal palpation carried out? When?

Answer 8

*Possible at day 20 (IF v skilled)
*Usually left until day 40
*Feel foetus by day 120

*Replaced by scanning - only used in late pregnancy now

Question 9

When would you perform rectal ultrasonography? Why?

Answer 9

*Can be done from day 10 - usually don’t scan too early
*Early embryonic death highest in first 14days

*Scan from day 16 - can see if twins + get rid
*Second scan day 24-26 = heartbeat, still can reduce twins + before cups
*Third scan = 6 weeks - just reassess

Question 10

What is distinctive with ultrasonography of foetus?

Answer 10

*White bits at top and bottom of black hollow cavity on ultrasonography

Question 11

From what date can you perform transabdominal ultrasonography?

Answer 11

• From 6 months onwards

Question 12

When does early embryonic death, abortion + stillbirth occur?

Answer 12

• Early embryonic death - from fertilisation to day 40
• Abortion - from day 40 - 300
• Stillbirth - from day 300 onwards

Question 13

What can cause failure of pregnancy?

Answer 13

• Early embryonic death
• Viral - EHV, EVA
• Bacterial
• Fungal
• Twins
• Maternal illness / stress
• Foetal abnormalities
• Umbilical torsion

Question 14

What can cause early embryonic death? Dx?

Answer 14

• Congenital / genetic abnormalities
• Breeding on foal heat - first season after foaling
• Uterine environmental problems - fibrosis / endometritis
• Dx = empty on repeat scan / abnormal size or shape conceptus on scan

Question 15

When does EHV-1 cause abortion?

Answer 15

*Usually late term (>5months)

Question 16

How is EHV-1 diagnosed, treated + prevented?

Answer 16

• Dx = nasopharyngeal swabs for horses showing respiratory signs
• Tx = none - isolate + disinfect + separate pregnant mares from youngstock
• Prevention = Vaccination - 5,7 + 9 months of pregnancy

Question 17

When is EVA notifiable? Prevention?

Answer 17

*Stallions + mares mated in last 14days
*Stallions become persistently infected shedders

• Prevention = vaccine

Question 18

What are agents of bacterial abortion? Causes? Tx?

Answer 18

• Strep, E. coli, Staph
• Causes = ascending infection from cervix, haematogenous spread + intro of bacteria at breeding
• Tx = antibiotics / NSAIDs - often too late

Question 19

What can cause fungal abortion?

Answer 19

*Aspergillus spp - rare

Question 20

Why can twin pregnancy cause failure of pregnancy?

Answer 20

*Twins compete with one another for attachment space (placenta need 70% contact with uterus) - one will run out of space in early pregnancy + die
*Other twin will continue to grow until deprived of space by remnant of dead twin + is aborted

Question 21

What kind of twins are more likely to die?

Answer 21

*Twins with one in each horn (bilateral) as more likely to get reasonable size before compete for uterus space

Question 22

How can the rectum be relaxed for crushing of a twin?

Answer 22

*sedatives / hyoscine

Question 23

What are signs of abortion?

Answer 23

• Maybe none
• Vaginal discharge
• Running milk - placentitis causes early lactation
• Colic / foaling signs

Question 24

How would you investigate abortion?

Answer 24

*Send whole carcass + placenta to pathologist
*Exam placenta + cord
*External exam + internal exam
*Sample chorion, thymus, liver, lung, spleen

*Don’t sample mare - not very useful

Question 25

How can you induce abortion?

Answer 25

*Before 3 months = Prostaglandin injection
*After 3 months = Repeated prostaglandin injections, Dilation of cervix + uterine lavage, Dislocation foetal neck per rectum

Question 26

How can you induce foaling?

Answer 26

*Oxytocin (1-2ml) every 15-20min till delivery starts
-however not done often - premature foal bad

Question 27

What are the risks of inducing foaling?

Answer 27

*Uterine rupture
*Dystocia
*Foal immaturity
*Retained membranes