Lecture 14: Equine Pregnancy & Parturition (Macpherson) Flashcards
function of the ampulla?
allows sperm passage
what is the function of the infundibulum in the mare?
its “the baseball mitt” used to catch the ovum.
important –> it covers the ovulation fossa in the mare
it then moves the ovum to the oviduct
what is the site of fertilization in the mare?
the ampullary isthmic junction
what is the oviductal papilla?
it is the opening of an oviduct to the mare. it protects the oviduct from infection during mating.
when is the embryo transported to the uterus?
day 5.5 to 6
what hormone is released while the embryo is in the oviduct?
prostaglandin E it stimulates muscle contraction to help transport the embryo out of the oviduct to the uterine horn.
what covers the compact morula?
the zona pellucida
what is unique about the blastocyst in the mare?
it has a capsule to keep the conceptus cervical
what 3 structures are in the blastocyst that were discussed in class?
- capsule (unique to the mare!)
- blastoceoele cavity
- inner cell mass
what 2 things were mentioned in class about the expanded blastocyst?
- it still contains an inner cell mass
2. it is what is most often seen in a uterine flush
what is a UFO? and what is it an indication of?
an unfertilized oocyte!
- it stays dormant in the oviduct
- usually an indication that there is also an embryo!
when is early detection of pregnancy in a mare?
day 13 - 15 post-ovulation
what is the state of the uterus and ovary during early detection of pregnancy? what should you see?
- uterus should be very toned (because it is under the influence of progesterone)
- a CL should be present on the ovary
Can mare double ovulate? what is important about this?
Yes - make sure you don’t get twins!
when should you check for twins?
2 weeks after ovulation
how does the embryo receive early nutrition? (2 ways)
- supported initially by the yolk sac
2. uterine glands produce histiotroph - nutrients that are secreted by the endometrium and absorbed by the early embryo.
what are endometrial cups? and what hormone do they secrete?
- structures produced by cells of trophoblastic embryo that migrate from embryo to endometrium.
- they form molar like structures (unique to the mare!) and secrete a hormone called equine gonadacotropin (ECG).
what does equine gonadacotropin (ECG) do? how long is it secreted for?
- it promotes growth of secondary CL which must be maintained to 200 days of pregnancy
- ECG is produced until 200 days of gestation
why is ECG produced only until the 200th day of gestation?
because the fetal placental unit “takes over” for the last 1/3 of gestation.
what is the mare placentation?
- diffuse
- epitheliochorial
- non-deciduate
- microplacentomes - that interdigitate with the endometrium
when do twins usually die?
at about 2/3 through gestation
are twins ever appropriate in the mare?
NEVER! NEEEEEVERRRRR!
what are the 2 things that threaten pregnancy the most?
- twins
- placental infection
what is the length of gestation?
320 to 360 days (highly variable; large range - unique to the mare)
what is unique about gestation length in horses?
- gestational length is repeatable in the individual.
- meaning if Lucy has a foal at day 342 then she will have future foals around that time too. If she doesn’t, that is considered abnormal and is cause for concern.
what things will vary the length of gestation?
- day length
- age
- number of pregnancies
what factors are important for parturition (4 things)?
- length of gestation
- fetal maturation
- colostrum production
- cervical dilation
name 2 important things about fetal maturation talked about during class.
- fetal maturation occurs in the last week of gestation.
- occurs in response to rising levels of cortisol released by the adrenal gland.
- if fetus is born without being exposed to cortisol, it will not have necessary functions for survival
when will mare start producing colostrum?
about 2 weeks before delivery
how can you measure electrolytes in colostrum production to predict fetal delivery?
- Na and K should invert: K production should increase and Na production should decrease.
- Ca should be > 40mg/dl
when does the cervix dilate? what is the significance of cervical dilation?
- it dilates prior to parturition
- this allows for faster delivery and improved neonatal adaptability
how should fetus be positioned for delivery?
in the anterior longitudinal position (like they are getting ready to DIVE into life!)
how long is the mare in stage I for?
1-4 hours
how long is the mare in stage II for?
30 to 60 minutes
how long is the mare in stage 3 for?
< 3 hours
what happens if the mare has not expelled fetal membranes after 3 hours?
it’s considered an emergency!
possible complication of parturition is what is called “red bag dystocia” what does this mean?
a portion of the placenta has detached from the uterine wall prematurely, reducing/eliminating exchange of nutrients (ie oxygen) to the fetus. you will literally see “the red bag” hanging out of the vulva before you see the fetus. This is considered a true emergency!
