Lecture 14: Equine Pregnancy & Parturition (Macpherson)

Question 0

function of the ampulla?

Answer 0

allows sperm passage

Question 1

what is the function of the infundibulum in the mare?

Answer 1

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

Question 2

what is the site of fertilization in the mare?

Answer 2

the ampullary isthmic junction

Question 3

what is the oviductal papilla?

Answer 3

it is the opening of an oviduct to the mare. it protects the oviduct from infection during mating.

Question 4

when is the embryo transported to the uterus?

Answer 4

day 5.5 to 6

Question 5

what hormone is released while the embryo is in the oviduct?

Answer 5

prostaglandin E it stimulates muscle contraction to help transport the embryo out of the oviduct to the uterine horn.

Question 6

what covers the compact morula?

Answer 6

the zona pellucida

Question 7

what is unique about the blastocyst in the mare?

Answer 7

it has a capsule to keep the conceptus cervical

Question 8

what 3 structures are in the blastocyst that were discussed in class?

Answer 8

• capsule (unique to the mare!)
• blastoceoele cavity
• inner cell mass

Question 9

what 2 things were mentioned in class about the expanded blastocyst?

Answer 9

1. it still contains an inner cell mass

2. it is what is most often seen in a uterine flush

Question 10

what is a UFO? and what is it an indication of?

Answer 10

an unfertilized oocyte!

• it stays dormant in the oviduct
• usually an indication that there is also an embryo!

Question 11

when is early detection of pregnancy in a mare?

Answer 11

day 13 - 15 post-ovulation

Question 12

what is the state of the uterus and ovary during early detection of pregnancy? what should you see?

Answer 12

• uterus should be very toned (because it is under the influence of progesterone)
• a CL should be present on the ovary

Question 13

Can mare double ovulate? what is important about this?

Answer 13

Yes - make sure you don’t get twins!

Question 14

when should you check for twins?

Answer 14

2 weeks after ovulation

Question 15

how does the embryo receive early nutrition? (2 ways)

Answer 15

1. supported initially by the yolk sac

2. uterine glands produce histiotroph - nutrients that are secreted by the endometrium and absorbed by the early embryo.

Question 16

what are endometrial cups? and what hormone do they secrete?

Answer 16

• 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).

Question 17

what does equine gonadacotropin (ECG) do? how long is it secreted for?

Answer 17

• it promotes growth of secondary CL which must be maintained to 200 days of pregnancy
• ECG is produced until 200 days of gestation

Question 18

why is ECG produced only until the 200th day of gestation?

Answer 18

because the fetal placental unit “takes over” for the last 1/3 of gestation.

Question 19

what is the mare placentation?

Answer 19

• diffuse
• epitheliochorial
• non-deciduate
• microplacentomes - that interdigitate with the endometrium

Question 20

when do twins usually die?

Answer 20

at about 2/3 through gestation

Question 21

are twins ever appropriate in the mare?

Answer 21

NEVER! NEEEEEVERRRRR!

Question 22

what are the 2 things that threaten pregnancy the most?

Answer 22

• twins

- placental infection

Question 23

what is the length of gestation?

Answer 23

320 to 360 days (highly variable; large range - unique to the mare)

Question 24

what is unique about gestation length in horses?

Answer 24

• 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.

Question 25

what things will vary the length of gestation?

Answer 25

• day length
• age
• number of pregnancies

Question 26

what factors are important for parturition (4 things)?

Answer 26

• length of gestation
• fetal maturation
• colostrum production
• cervical dilation

Question 27

name 2 important things about fetal maturation talked about during class.

Answer 27

1. fetal maturation occurs in the last week of gestation.
2. 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

Question 28

when will mare start producing colostrum?

Answer 28

about 2 weeks before delivery

Question 29

how can you measure electrolytes in colostrum production to predict fetal delivery?

Answer 29

• Na and K should invert: K production should increase and Na production should decrease.
• Ca should be > 40mg/dl

Question 30

when does the cervix dilate? what is the significance of cervical dilation?

Answer 30

• it dilates prior to parturition

- this allows for faster delivery and improved neonatal adaptability

Question 31

how should fetus be positioned for delivery?

Answer 31

in the anterior longitudinal position (like they are getting ready to DIVE into life!)

Question 32

how long is the mare in stage I for?

Answer 32

1-4 hours

Question 33

how long is the mare in stage II for?

Answer 33

30 to 60 minutes

Question 34

how long is the mare in stage 3 for?

Answer 34

< 3 hours

Question 35

what happens if the mare has not expelled fetal membranes after 3 hours?

Answer 35

it’s considered an emergency!

Question 36

possible complication of parturition is what is called “red bag dystocia” what does this mean?

Answer 36

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!