Clinical Physiology of Pregnancy

Question 1

Early Development in the Bovine
-embryo to uterus
-what does it produce
-when does it fill the horn

Answer 1

-Embryo enters uterus from oviduct
-Immediately begins elongating
-Produces INF tau – this is the signal for maternal recognition of pregnancy in cows
-Fills that horn by day 24 (same side as CL)
-Eventually fills entire uterus

Question 2

what is critical for pregnancy to continue (mares)

Answer 2

The capsule is a glycoprotein layer surrounding the embryo and is critical for pregnancy to continue

Question 3

what is formed that is unique to domestic farm animals

Answer 3

Formation of the capsule (present from Day 7 – 22) is unique among domestic farm animals

Question 4

what is essential for maternal recognition in the mare

Answer 4

Phase of Early Mobility

Question 5

details about Phase of Early Mobility in mares

Answer 5

– Embryonic signal is not known
– Mobility phase from entry into uterus until Fixation at 16 days
– Increased uterine contractions wherever embryo is located
– Embryo traverses entire uterus multiple times per day!!
– Anything that disrupts this results in pregnancy failure

Question 6

when does fixation of the embryo take place in mares

Answer 6

-Embryo stops moving and settles in place at the base of one horn
-Fixation ‐ occurs at day 16

Question 7

what does embryo fixation coincide with in the mare

Answer 7

-Coincides with increase in uterine tone, rapid increase in diameter of embryo and changes in the capsule making the embryo sticky
-Fixation should occur at the base of a horn
-Then embryo orientation occurs with embryo proper at base of vesicle

Question 8

gestation length and source of progesterone throughout pregnancy in the cow

Answer 8

Gestation length: 280d
CL: throughout
Placenta: 150 – 250 d

Question 9

gestation length and source of progesterone throughout pregnancy in the sheep

Answer 9

Gestation length: 150
CL: <50-60d
Placenta: >50-60d

Question 10

gestation length and source of progesterone throughout pregnancy in the goat

Answer 10

Gestation length: 146
CL: throughout
Placenta: 8-10% of P4

Question 11

gestation length and source of progesterone throughout pregnancy in the sow

Answer 11

Gestation length: 112
CL: throughout
Placenta: no contribution

Question 12

gestation length and source of progesterone throughout pregnancy in the bitch

Answer 12

Gestation length: 63
CL: throughout
Placenta: unsure

Question 13

gestation length and source of progesterone throughout pregnancy in the mare

Answer 13

Gestation length: 341
CL: 120d (2 CLs cups)
Placenta: >70d

Question 14

Endocrinology of Pregnancy in the
Mare
-what hormones are high/low
-whats formed

Answer 14

-Primary CL (from ovulation)
-Formation of Endometrial cups
-Secondary CL’s
-High levels of estrogen
-Low levels of progesterone after 150 days until close to term

Question 15

How Do The Cups Contribute to Pregnancy Maintenance in Mares?

Answer 15

-Cups begin to form about day 35
-Specialized fetal trophoblast cells that invade the maternal endometrium
-Produce Equine Chorionic Gonadotropin
-eCG is detectable from day 35 thru 120

Question 16

what does eCG act like in the horse

Answer 16

-eCG has LH activity in horse‐‐‐‐‐ Results in Secondary CL’s on ovaries‐‐‐‐‐‐‐ which make Progesterone to maintain pregnancy thru day 120

Question 17

what does eCG act like in the cow

Answer 17

remember eCG has FSH activity in ruminants for breeding management programs

Question 18

endometrial cups; when do they die off, what happens if fetal loss happens

Answer 18

-Have a pre‐programmed lifespan
-Die off (or are destroyed?) about day 100‐120
-If the fetus dies while cups are present; they remain, and continue to produce eCG. This means the mare will not come back into heat until the cups regress

Question 19

fetal gonads in the horse; what they pump out, and what its useful for

Answer 19

-Fetal gonads pump out a steroid hormone precursor, DHEA which is
converted by the placenta to various estrogens (some are specific to the horse – eg. Equilin, and Equilenin)
–These are essential for normal fetal growth and development, normal myometrial contractions during labour and normal mammary gland development
–But estrogens are not “required” for maintenance of the pregnancy

Question 20

fetal gonads in the horse; what it produces, and why its important

Answer 20

-Fetal adrenal gland produces other
progestagens of pregnancy in the mare (mostly 5 alpha pregnanes such as 5 α DHP and pregnenolone)

-These are biologically active in horses and appear to be responsible for the “progesterone block” of pregnancy
-Bind to equine progesterone receptor