1.4.1 Termination of Pregnancy

Question 1

how can we induce abortion in cows? What differences are there in our strategy depending on what stage we are at in the pregnancy and why?

Answer 1

PGF2α + Dexamethasone
* At any stage of pregnancy

PGF2α (may need 2 injections to ensure you induce complete luteolysis and avoid mummification)
* < 150 d
* > 250 d

Dexamethasone
* > 250 d – provided fetus is alive

-In cows, the CL is present and source of P4 throughout gestation with the Placenta contributing progesterone from day 150‐250

Question 2

what natural hormone is dexmethasone similar to and why is this important?

Answer 2

cortisol: allows us to use dexmethasone to terminate pregnancy

Question 3

What will you use in cases of fetal mummification or maceration in bovine to terminate pregnancy and why?

Answer 3

placenta is dead, so pregnancy is maintained only by CL. Use prostoglandin.

Question 4

what methods can we use to induce abortion in the mare at various points during the pregnancy?

Answer 4

< 28 days of pregnancy
* Pinch one vesicle transrectally (twins)

< 35 days (before cups form and produce eCG)
* PGF2α

35 – 120 days (while cups are present)
* PGF2α – twice daily for 3‐5 days +/‐ manual extraction

> 120 days (no CL’s present, placenta source only)
* PGF2α – twice daily for 3‐5 days, then oxytocin to expel
fetus +/‐ assist, manually dilate cervix and extract
* High rate of RFM

Question 5

how can we induce abortion in a sheep?

Answer 5

• In sheep, one injection of PGF2a is 90% effective in inducing abortion before 50‐60 days; two injections 48 hours apart ‐ is 100% effective
• After 50‐60 days corticosteroid is somewhat effective – may require multiple injections and manual dilation/extraction – low efficacy

Question 6

how can we induce abortion in a goat?

Answer 6

• In goats – PGF2a is effective at any stage of pregnancy

Question 7

how can we induce abortion in a pig?

Answer 7

• In pigs – PGF2a is effective at any stage of pregnancy

Question 8

when we give PGF2a to induce abortion, how many injections are recommended and why?

Answer 8

2 PGF2a injections is recommended (a few days or 1 week apart) to ensure complete luteolysis
* Reduced risk of fetal mummification
* Increases success rate

Question 9

what was the leading cause for abortion in mares prior to ultrasound?

Answer 9

twinning, usually due to double ovulation

Question 10

why is twinning undesirable in mares

Answer 10

• Not desirable – rarely go to term due to
  placental insufficiency
• Dystocia common

Question 11

what can help avoid twinning in mares? how can we ‘cure’ twinning in early pregnancy and when should we do this?

Answer 11

Routine early diagnosis by ultrasound at 14 days by ultrasound helps prevent this

Manual Twin Reduction‐ “Pinching a Twin”
* Best performed at 14‐17 days (before fixation)
* Can still be done up to approx. day 28
* Manual crushing per‐rectum

Question 12

if twinning in the mare is unilateral, what are the chances that the twins will persist? what about bilateral?

Answer 12

• if unilateral, >85% chance that by day 60 the pregnancy will reduce to a singleton or no pregnancy, on its own (natural reduction)
• If bilateral, highly likely to continue as twins until abortion in late gestation

Question 13

Twin reduction in the mare – later options

Answer 13

• Day 28 – 55: Ultrasound monitored disruption
  > Good for bilateral cases

Day 70 – 120: Craniocervical dislocation
* Rectally
* Colpotomy (vaginal incision)
* Flank incision

Day 90 – 180: Transabdominal ultrasound‐guided puncture
* Intra‐fetal injection of procaine penicillin
* The later performed, the greater the risk of placental
insufficiency and abortion of pregnancy
* 50% success – foal born at term may be small and ill‐thrift, often not an athlete

Question 14

twinning rate in holsteins

Answer 14

• Twinning rate in Holsteins is increasing over time
• Now around 5%

Question 15

why are twinning rates in holsteins increasing?

Answer 15

• Selection for increased milk production = more double ovulations; also higher use of synchronization programs

Question 16

what is twinning associated with in cows? how do chances of successful calving change?

Answer 16

• Associated with higher embryo/pregnancy losses
• 92% of cows dx with singleton will calve vs. 76% of cows dx
  with twins (as low as 54% in some studies)
• Higher rates of dystocia and postpartum disease
• Risk of Freemartin Syndrome in calves

Question 17

risk of pregnancy loss in cows with twins?

Answer 17

• Manual rupture of one sac at 35‐40 days possible but high rates of complete pregnancy loss (30‐55%)

Question 18

when is it ok to induce parturition in cows? what drugs should we use and how long after administration should we expect calving?

Answer 18

*Within 2 weeks of calving
*Dexamethasone and Prostaglandin combination
*Most predictable
*Calving about 36 hours after administration
*With Dex only = about 43‐52 hrs
*With PGF only = 45‐72 hrs

Question 19

what difficulty is associated with induced parturition?

Answer 19

*Very high incidence of retained placenta

Question 20

what is associated with induction of parturition earlier in the cows pregnancy?

Answer 20

-increased calf mortality
-fewer calves are sold
-value of calves decreases

Question 21

how can we induce parturition in the ovine?

Answer 21

Ovine (placenta takes over by 50 d)
* From day 137 onward
* Corticosteroid – Dex 10‐20 mg
* 80% lamb in 42 hrs (avg) – 2 or more injections may improve survival of premature lambs
* PGF not effective

Question 22

how can we induce parturition in the caprrine?

Answer 22

(CL dependent throughout)
* PGF2α >140 days – kidding in 30‐50 hrs

Question 23

how can we induce parturition in the porcine?

Answer 23

(CL dependent throughout; litter‐bearing)
* PGF2α day 111 + oxytocin 24 hrs later – farrow in ~ 6 hrs

Question 24

why can it be dangerous to induce parturition in mares?

Answer 24

• Gestation in mares has a wide range of normal
• Fetal maturation happens in the last 2 days!
• We cannot speed this process in the mare (not easily)

Question 25

guidelines for safe induction in mares

Answer 25

• 1. Min 330 days gestation
• 2. Udder development + colostrum
• 3. Relaxation of sacrosciatic ligaments and vulva
• 4. Electrolyte analysis of colostrum indicates fetal maturity

Question 26

how can we use milk electrolyte levels to find out about fetal maturity in mares?

Answer 26

Electrolyte changes in milk indicate fetal maturity

• Increase in Calcium (Ca2+) to >400 ppm, or >200 ppm (10 mmol/ml) on two consecutive days, indicates fetal maturity
• Potassium should be greater than Sodium
• Decrease in Sodium to <35 mmol/ml
• Increase in Potassium to > 80 mmol/ml
• Daily charting of Sodium & Potassium

Question 27

what can we look at in mare’s milk to find out about fetal maturity?

Answer 27

-electrolytes and pH

Question 28

how does mare’s milk pH change when the fetus is ready for birth?

Answer 28

When pH drops below 6.4:
* Foal within next 24 hrs.

Question 29

what should we remember about using oxytocin to induce parturition in the mare?

Answer 29

• Mares are exquisitely sensitive to oxytocin in late pregnancy even if fetus is not mature
• Potential to induce too early and have a dead foal!!

Question 30

how do we induce parturition in a mare, if she meets the requirements? when can we expect the foal?

Answer 30

• Oxytocin
• 10‐15 IU, IV, repeat every 15‐20 min
• Usually foal within 60 min (after 2nd or 3rd injection)

Question 31

is PGF2a useful for inducing parturition in the mare? why?

Answer 31

• NOT reliable (remember, no CL’s are present after 120 days in mares)
• NOT recommended

Question 32

are corticosteroids useful for induction of parturition in the mare? why? when are they ok to use and how long after administration should we expect the foal? what issues might we run into?

Answer 32

• Corticosteroids – only in specific urgent situations!
• Only cross equine placenta if very high doses are given repeatedly
• Foal approximately 8 days later
• Appears safe between 315 and 325 days gestation to induce fetal maturation
• Risk of laminitis
• Mare will NOT make colostrum
• If used close to term leads to dystocia and fetal death in high %

Question 33

summary of how to induce parturition in the cow: what drugs and how long after administration will birth occur?

Answer 33

PGF2α + Dex
36 hours

Question 34

summary of how to induce parturition in the ewe: what drugs and how long after administration will birth occur?

Answer 34

Dex
42 hours

Question 35

summary of how to induce parturition in the doe: what drugs and how long after administration will birth occur?

Answer 35

PGF2α
30-50h

Question 36

summary of how to induce parturition in the sow: what drugs and how long after administration will birth occur?

Answer 36

PGF2α + Oxytocin in 24hrs
-6hrs after oxytocin

Question 37

summary of how to induce parturition in the mare: what drugs and how long after administration will birth occur?

Answer 37

Low dose Oxytocin
<1h