Non-infectious Equine Infertility

Question 1

Natural reduction usually occurs ____

Answer 1

After day 16

Question 2

Twinning

Answer 2

Almost always results in late term abortion

Question 3

Late term abortion can lead to

Answer 3

• dystocia
• retained placenta
• delayed uterine involution
• metritis
• death of both twins, and/or mare

Question 4

Source of twins

Answer 4

• mostly dizygotic from multiple ovulations

- reported monozygotic

Question 5

____ have highest incidence of double ovulations (16%)

Answer 5

Thoroughbreds

Question 6

Synchronous vs asynchornous ovulations

Answer 6

• 2 ovulations within 24 hrs: synchronous

- 2 ovulations within >24 hrs: asynchronous

Question 7

Incidence of twins

Answer 7

• 3-11% of mares conceive twins
• account for 1-2% of equine births –> 14% of live foals still alive after 2 weeks
• fetal and perinatal losses approach 90%
• up to 30% of abortions are attributable to twins –> 2nd to placentitis!!

Question 8

Breed affects

Answer 8

• thoroughbreds and drafts (15-25%)

- standardbred, quarter horse, appaloosa (5-15%)

Question 9

Seasonal imact

Answer 9

• Jan-March (7%)

- April-May (22%) –> higher incidence during physiological breeding season

Question 10

Reproductive status

Answer 10

Rare to see twins following foal heat mating

- rarely seen in mares foaling early in the year

Question 11

Other influencing factors

Answer 11

• body condition

- heritability: seen in certain lines

Question 12

Ultrasound

Answer 12

Led to decrease in number of twin pregnancies in the last 30 years
- can detect twins much earlier

Question 13

Causes of embryo/fetal losses

Answer 13

• lack of contact with endometrium
• decreased nutrient exchange
• placental insufficiency
• unilateral twins (lost usually by 40 days)
• bilateral twins (loss by 5-9 months)
• natural reduction is efficient, especially in unilateral twins

Question 14

_____ has no benefit

Answer 14

Breeding strategies

• breed regardless of # of follicles
• don’t try to catch 2nd follicle by passing the 1st follicle
• advantage of greater preg rates when double ovulations occur, so breed anyway
• use ovulation induction agents as you normally would

Question 15

Post breeding exam

Answer 15

Continue to check mare to determine if additional ovulations occur

• record ovulations
• document location of uterine cysts
• plan pregnancy checks early if twins are suspected/anticipated (13-14 day check)

Question 16

Failure to detect twins

Answer 16

• endometrial cysts (usually not spherical)
• pregnancy detection occurring too early to detect 2nd embryo
• lack of thorough ultrasound
• poor image quality
• immediately adjacent vesicles that appear as one

Question 17

Pregnancy check

Answer 17

Ultrasound mare on day 13-15 post ovulation

• vesicles are still mobile at this point
• if 2 vesicles found, twins are diagnosed –> manipulate/manually crush 1 twin
• recheck in 2-3 days if possible –> crush twin if discovered, assure remaining twin is growing/viable

Question 18

Problems occur if mare ______

Answer 18

Is not checked until 35-40 days

• eCG being produced by cups
• if pregnancy is terminated at this point, the mare won’t cycle predictably that year
• season is lost

Question 19

Twin reduction options depends on _______

Answer 19

• stage of pregnancy at time of diagnosis
• location of embryonic vesicles
• management factors
• owners risk tolerance
• time of breeding season
• clinician expertise
• equipment available

Question 20

Options - before fixation

Answer 20

Days 12-16

• natural reduction
• manual crushing

Question 21

Options - after fixation

Answer 21

Days 17+

• natural reduction
• manual crushing
• US guided aspiration or cardiac puncture
• cranio-cervical dislocation

Question 22

Day 14-16

Answer 22

Crush one vesicle

• move smaller vesicle to tip of one horn and crush
• 93% success rate
• if vesicles are adjacent just wait 10-20 minutes for them to separate naturally

Question 23

What is success?

Answer 23

• elimination of a single conceptus
• carrying to term the remaining conceptus
• with delivery of a normal viable foal

Question 24

Success rate is ______ proportional to the time you start management

Answer 24

Inversely

Question 25

Day 17-34 of gestation - bilateral twins

Answer 25

- crush one vesicle --> 90% success rate, may give NSAIDs - transvaginal US guided aspiration --> 75% success rate - do nothing --> 0% chance of natural reduction

Question 26

Day 17-34 - unilateral twins

Answer 26

- wait until day 33 --> 77% should naturally reduce - abort entire pregnancy with prostaglandins - transvaginal US guided aspiration --> 33% success rate

Question 27

Days 35-60 - bilateral twins

Answer 27

- crush one vesicle --> 25% success rate, difficult to perform - transvaginal US aspiration --> 75% success rate - abort with prostaglandins --> requires multiple injections, season will be lost b/c of eCG presence

Question 28

Days 35-60 - unilateral twins

Answer 28

- do nothing --> 77% should reduce naturally by day 40 - abort with prostaglandins - transvaginal US aspiration --> 33% success at 45 days

Question 29

Day 61-90

Answer 29

If twins survive, abortion is likely despite location - 70% will abort if they make it past 90 days - abort with prostaglandins --> multiple, daily injections to effect, mare will have more time to recover prior to next breeding season - US guided fetal cardiac puncture --> 33% success rate

Question 30

Cranio-cervical dislocation

Answer 30

Performed between 55-110 days of gestation - trans-rectal: 55-90 days - intra-abdominal: 65-110 days - success rate of 60% with a birth of a single normal sized, healthy foal

Question 31

Body pregnancy

Answer 31

Embryo becomes fixed in uterine body - placenta is unable to fully expand into both uterine horns - placental insufficiency results in late term abortion (7-8 months)

Question 32

Hypoleuteism

Answer 32

Progesterone levels insufficient to support pregnancy - progesterone below 2.0 ng/ml - placenta begins taking over progestagen production at 120 days and is only source after 150 - can be an early pregnancy problem - treatment involves supplementation with altrenogest

Question 33

Umbilical cord torsion

Answer 33

Normal twisting (2-4 twists) is common - average cord length should be 50-60 cm - excessive twisting results in vascular compromise leading to fetal death - abortion/stillbirth - rare cause of pregnancy loss in US, seen in Europe