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When does fixation occur in a mare? Implantation? Where does the embryo get its nutrition at this stage?

* Fixation occurs at D16/17

* Implantation D35

* nutrition through histiotroph ("uterine milk") and yolk sac


When does early embryonic death (EED) normally occur? Causes?

* Most often before D11 (before detection) (5-25%)

* D14- 40 (6-10%)

* Causes: endometritis, endometrosis, P4 deficiency (progesterone), nutrition; stress, heat, embryonic factors (chromosomal abnormalities)



Where does eCG come from?

* Secreted by endometrial cups (EC)-- EC formed from trophoblast cells invading the uterus


What are 5 alpha pregnanes?

* Progestagens of feto-placental unit

* Start rising around D 40

* sole source of progestagens from D 150

*Cross-react with antibodies used in RIA


At what day are ECs retained even if pregnancy is lost?

* after D35


What is responsible for maintenance of pregnancy until D 50? When is the secondary CL functional? When is peak progesterone? When do CLs regress?

* Primary CL resp. for maint. of preg. until D 50

* secondary CL functional after D 40

* Peak progesterone around D 80

*CL slowly regresses until D 150


When is there no value to measure progesterone?

After D 150


What is the profile of oestrogen in horse pregnancy?

* Ovarian oestrogens begin to rise at D 38-40

* D 70-80 a second rise of oestrogens from the foetal-placental unit occurs (peak D 210)


When might you give exogenous progestones?

* NOT in a mare with a history of pregnancy loss

* Anything that might cause luteolysis: endotoxaemia, high plasma cortisol levels, failure of conceptus to signal maternal recognition of pregnancy

* Suspect lack of maternal recognition: start exogenous progesterone at D 5, if pregnant on D 14 : check for CL (+/- serum P4 levels), if not pregnant: withdraw P4




How do you give exogenous progesterone before D 100 to a mare?

* Before D 100:

* first use short-acting P4 (e.g. regumate or injectable)

* if fetus still alive after insult disappears--> can switch to longacting injectable (LA)

* Check fetal viability weekly

* Withdraw over 5 days (reduce dose by 20% daily)


How do you give exogenous progesterone after D 100 to a mare?

* High doses have to be given if premature udder development occurs and fetus is still alive

* 500 mg BID

* Adjust dose according to udder

*Viability of fetus has to be checked weekly

* Withdraw immediately if fetus is dead


Pregnancy Diagnosis in a mare

* Ultrasounds from as early as D 10 (D14 routine)

* Rectal palpation - from D 18 (too late for twins)

* Oestrone sulphate- from D 44 (peak 80)

* eCG- D 40 to 120 (false positive if fetal loss)


Routine pregnancy exam in mare

* D 14 post ovulation (before D 16)

* D 25- 28 post ovulation (viability)

* D 40 often time when stud fee is due

* D 60-70 fetal sexing if they want


What are > 90% of twins in mares a result of ? What percent result in unilateral fixation? When do you crush one of the twins?

Double ovulation... 70% unilateral fixation- 83% chance that one of the unilateral twins will disappear "deprivation hypothesis"

** Crush one of the twins before fixation, in the mobility phase-- after fixation-- 83% should reduce to singleton pregnancy-- reexamine D 33-34


If you do not catch twins before fixation what are you options?

* PGF2alpha (esp early in season)

* Transvaginal, us-guided needle aspiration (50% success that one goes to term)

* Manual crushing (not very successful)


When does placenta take over progesterone production?

D 100


A single shot of PGF2alpha on day 33 will lead to a drop in progesterone and loss of pregancy



What should you do if you have twin fixation bilaterally?

* Spontaneous reduction extremely unlikely, crush immediately, might still lose both, keep teasing mare


Signs a mare is close to parturition


What should you do about twins after D40?

* Season is lost

* Owner's decision- inform about risks (dystocia, premature foals, non-viable/athletic foals)

* If he wants to take on risk: decapitation can be done later, wait and see--mare may abort due to sudden drop in progestagens when one fetus dies;  both aborted-- when mare develops udder prematurely (because of falling progestagens)--> assess viability of fetus & give large dose of exogenous progestagens (500 mg BID-- BID = two times per day)


Speak through normal parturition in a mare-- stages, time, and what happens each stage

Stage I: 1-4 hours (up to 12 hours); uterine contractions, positioning of fetus, restlessness, frequent urination, defecation, sweating, laying down/rolling

Stage II: 5-20 minutes, fetal expulsion- starts with rupture of chorioallantois (breaking water), abdominal contractions, mare becomes recumbent, rapid delivery (if > 60 minutes foal likely to die)

* Stage III: expulsion of membranes, usually delivered 30 to 90 minutes after end of stage II... RFM if not released 4-6 hours postpartum


What should you always do to ensure you don't miss twins in a mare?

Check both ovaries


Signs and cause of placentitis? Consequence? Diagnosis? Treatment?

* Signs: premature udder development and/or udder development

* Usually ascending (e.g. Sc. equi sp zooepidemicus, E. coli, Klebsiella pneumoniae)

* Impending abortion threat believed to be due to decrease in placental progestagens

Diagnosis: transrectal ultrasound (transabdominal if haematogenous), measured CTUP (combined thickness of uterus and placenta)

* Treatment: ABs (e.g. Penicillin/gentamycin, trimethroprim sulfamethoxazole) exogenous progesterone, flunixin meglumine,  pentoxifylline  ** check fetal viability regularly at least weekly


Red bag- failure of cervical star to rupture

* Don't wait to get there, tell someone to cut the chorioallantois and deliver foal ASAP


Normal gestation length in a horse? What plays a role in length?

340 days (wide range 320-365 is normal)

* Season plays a role, fetal sex of the foal


Causes a "red hood" over the foals head if cervical star doesn't rupture but the other part ruptures


* Membranes came out with the foal

* Chorion looks oedematous


When do mares foal?

Between sunset and midnight