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?
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