Pregnancy In the Mare
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What happens to the CL if a mare is successfully bred?
the CL will not be lysed on the 14th or 15th day
What happens to the CL if a mare is pregnant?
it will continue to secrete progesterone while the mare undergoes maternal recognition
What is maternal recognition?
the process where leutolysis is prevented by the presence of conception
When does the embryo enter the uterus?
6 days post ovulation
What happens during maternal recognition?
the embryo migrates through both uterine horns and the uterine body
How many times does the embryo migrate through the entire uterus during maternal recognition?
multiple times per day
When does maximal movement occur during maternal recognition?
day 11 or 12
How long does maternal recognition last?
maintained until day 16
What signals to the mare that pregnancy occurs?
the migration or travelling of the embryo
What is the purpose of the polysaccharide-rich capsule?
- it serves as an air bag for the embryo after it enters the uterus and during the motile phase
- may help prevent the conceptus from being recognized as a foreign body
How long does the capsule stay in place?
- grows with embryonic vesicle until day 18
- disappears by day 23 of pregnancy
What happens if the mare fails to recognize a pregnancy?
- lysing of the CL
- PGF2a secretion
What can cause a pregnancy to fail to be recognized?
- blocked uterine horn
- uterine cyst
What is fixation?
- different from fetal-attachment
- occurs when embryonic vesicle becomes stationary
What occurs during fixation?
- growing conceptus can no longer enter the uterine horn
- vesicle begins to change shape from sphere-like to triangular due to the thickening of the dorsal uterine wall
What is fetal-maternal attachment?
gradual process that attaches the placenta to the mare
How long does fetal-maternal attachment take?
- begins around day 25 of pregnancy
- full attachment achieved by day 150
When does the CL step back from producing progesterone?
What are endometrial cups?
circular or horseshoe grouping of irregular growths on the uterine horn
What is the function of endometrial cups?
- secrete equine chorionic gondaotropin (eCG)
- this helps in the formation of secondary CLs and maintain the primary CL from day 35-120
How long can a mare test positive if she aborts a fetus by eCG test?
up to 3 months
What are some methods for pregnancy diagnosis?
- behavioral assessment
- serum/milk progesterone assay
- vaginal seculum exam
- palpation of repro tract per rectum
- eCG detection
- estrogen detection in blood or urine
base your pregnancy diagnosis method on:
- equipment available
- clinical expertise
- stage of pregnancy
How long is a horse's gestation?
- 335 to 342 days
- about 11 months
What is considered a premature foal?
foal born before day 320
what is considered a dysmature foal?
foal born to term but immature and often undersized
What can affect gestation length?
- gender of foal
- maternal nutrition
- environmental stresses
- mare experience
What are the stages of gestation?
What is the embryo phase?
- conception to day 58
- rapid embryo growth and differentiation of tissues and organs
What two major events occur during the embryo phase?
- formation of endometrial cups
- transuterine movement of embryo from horn to horn (maternal recognition)
When are abortions common?
What is the fetal phase?
- day 58 until parturition
- further minor issue differentiation
- longer of 2 phases
When does the most overall growth occur?
during the 3rd trimester
When do endometrial cups begin to form?
- around day 25 they begin to form
- they appear on uterine epithelium on day 38
When do endometrial cups reach their maximum size?
- day 70
- completely gone by day 130
What signals the supplementary CLs to form?
pituitary gland and endometrial cups
How long does the primary and supplementary CLs support the fetus?
- first 5 months of pregnancy
- after 150 days, the placenta takes over
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