Non-infectious Equine Infertility Flashcards
Natural reduction usually occurs ____
After day 16
Twinning
Almost always results in late term abortion
Late term abortion can lead to
- dystocia
- retained placenta
- delayed uterine involution
- metritis
- death of both twins, and/or mare
Source of twins
- mostly dizygotic from multiple ovulations
- reported monozygotic
____ have highest incidence of double ovulations (16%)
Thoroughbreds
Synchronous vs asynchornous ovulations
- 2 ovulations within 24 hrs: synchronous
- 2 ovulations within >24 hrs: asynchronous
Incidence of twins
- 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!!
Breed affects
- thoroughbreds and drafts (15-25%)
- standardbred, quarter horse, appaloosa (5-15%)
Seasonal imact
- Jan-March (7%)
- April-May (22%) –> higher incidence during physiological breeding season
Reproductive status
Rare to see twins following foal heat mating
- rarely seen in mares foaling early in the year
Other influencing factors
- body condition
- heritability: seen in certain lines
Ultrasound
Led to decrease in number of twin pregnancies in the last 30 years
- can detect twins much earlier
Causes of embryo/fetal losses
- 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
_____ has no benefit
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
Post breeding exam
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)
Failure to detect twins
- 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
Pregnancy check
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
Problems occur if mare ______
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
Twin reduction options depends on _______
- stage of pregnancy at time of diagnosis
- location of embryonic vesicles
- management factors
- owners risk tolerance
- time of breeding season
- clinician expertise
- equipment available
Options - before fixation
Days 12-16
- natural reduction
- manual crushing
Options - after fixation
Days 17+
- natural reduction
- manual crushing
- US guided aspiration or cardiac puncture
- cranio-cervical dislocation
Day 14-16
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
What is success?
- elimination of a single conceptus
- carrying to term the remaining conceptus
- with delivery of a normal viable foal
Success rate is ______ proportional to the time you start management
Inversely
Day 17-34 of gestation - bilateral twins
- crush one vesicle –> 90% success rate, may give NSAIDs
- transvaginal US guided aspiration –> 75% success rate
- do nothing –> 0% chance of natural reduction
Day 17-34 - unilateral twins
- wait until day 33 –> 77% should naturally reduce
- abort entire pregnancy with prostaglandins
- transvaginal US guided aspiration –> 33% success rate
Days 35-60 - bilateral twins
- 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
Days 35-60 - unilateral twins
- do nothing –> 77% should reduce naturally by day 40
- abort with prostaglandins
- transvaginal US aspiration –> 33% success at 45 days
Day 61-90
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
Cranio-cervical dislocation
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
Body pregnancy
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)
Hypoleuteism
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
Umbilical cord torsion
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
