Equine Flashcards
What is the proper configuration of the mare vulva in relation to the anus
the proximal 2/3 of the vulva length should be central to the tuber ischium
During pregnancy and diestrus the cervix is under the influence of ___ and creates a protective seal
progesterone
True/false: the equine cervix has 4 annular rings
false, they have longitudinal folds
Why is the equine cervix easy to transverse/get through? especially during AI?
it has longitudinal folds as compared to annular rings
True/False: the equine ovary is the same as other species, as in the cortex is on the outside and the medulla is on the inside
false, it is reverse
Where does ovulation occur in an equine ovary
the ovulation fossa as compare to other species that ovulate from any part of the ovarian surface
True/False: you are able to palpate follicles but not CLs? why or why not
true, because the CL do not protrude to the ovarian surface, the grow inward
When is the onset of mare puberty
12-24 months
What two things affect the onset of puberty?
age at time of breeding season
body condition/nutrition
At what age are most mares first bred?
> 3yrs
What is the equine breeding pattern/season
seasonally polyestrus, long day breeders
True/False: breeding is primarily controlled by photoperiod
true
Describe how photoperiod regulates reproduction in mares
-melatonin is synthesized and secreted in the pineal gland
-decreases the synthesis of GnRH
-so during short days, melationin increases yielding GnRH inhibition this anestrus
What is the average estrus cycle length
21 days
True/False: Mares experience spontaneous ovulation
true
When is the physiological breeding season
April - Sept/Oct
What three things are characteristic of the mare spring transition?
-increased release of hypotholamic GnRH
-follicular development occurs but no ovulation due to insufficient LH release
-receptive behavior but irregular and often lengthy heat periods
What are two things characteristic of mare fall transition?
behavior and ovulation become erratic
may develop large anovulatory follicles
How does mare behavior towards the stallion differ between the anestrus and diestrus periods?
-anestrus: the mare is indifferent/passive, and may or may not be receptive
-diestrus: mare is aggressive, kicking, etc
True/False: all mares, once they enter the non breeding season (winter), do not cycle
false, 20-25% of mares may continue to cycle through the winter
Industry push to have foals born close to ___
january 1st
If you want a mare to foal as close ot Jan 1st as possible when should you introduce light?
Dec 1st
What is the average estrus cycle length of the mare
21days
What is the size of a mare follicle at ovulation
40mm
Why does the size of the ovulatory follicle tend to be smaller at peak breeding season?
because follicle growth rate is faster at peak season and needs to deploy
True/False: mares tend to have shorter estrus periods and ovulate smaller sized follicles at the peak of breeding season
true
How is LH activity prior to ovulation in the mare differ from other species
there is no brief LH surge, there is a gradual increase starting 6-7 days prior to ovulation and it peaks about 1-3 days post ovulation
How is PGF2alpha activity differ in the horse?
there is no exchange mechanism in the horse, so PGF2alpha has to enter systemic circulation from the uterine vein to reach the ovary via ovarian artery
True/False: mares have 1-2 diestrus follicular waves but will not ovulate
false, they can ovulate which yields a CL and that can prolong diestrus
How would you describe a uterus on US of a mare in estrus vs diestrus
estrus: flaccid, edematous folds “spoking”
diestrus: firm tone, uniform echogenicity
What US finding on a follicle is indicative of impending ovulation?
follicle becoming tear drop shaped
Why is the urethral sinus clinically important in stallions
there can be formation of smegma beans. check during soundness exams
What two things must be normal on a testicular soundness exam for a stallion to be fit to breed
normal measurment
normal US anatomy
True/False: colts are born with their testicles descended, if not they are considered chryptorchid
false, while most are born with both descended, it is still normal if within 6 months of life
What is the average age of puberty onset in the stallion
12-18 months
When is a stallion technically considered a stud? at what age are they considered most sexually mature?
2Y
5-6Y
reduction in testicle size and daily sperm output occurs in ____ and _____
late autumn and winter
Stallion semen is considered ___ compared to ruminants
dilute
What is the longevity of fresh semen
48hrs
Where is semen deposited during AI if you are using chilled/fresh semen?
uterine body
Where is sperm deposited during AI if you are using frozen semen?
in/at the tip of the uterine horn, on the side of ovulation
What is the insemination window for shipped cooled semen
24 hours before to 12 hours after ovulation
What is teh insemination window for frozen semen
12 hours before to 6 hours after ovulation
What is the preferred method of pregnancy diagnosis and when is it diagnostic?
ultrasound, the embryonic vesicle at day 14 is definitive
What other ways are you able to diagnose pregnancy other than US
teasing
non-return to estrus behavior is suggestive
palpation per rectum
When are you able to palpate per rectum the embryonic vesicle?
day 28-30
When does the embryo enter the uterus
6 days post ovulation
why is it clinically significant that the embryo doesn’t enter the uterus until day 6?
it allows clinicians to treat the uterus if necessary
How long does the embryo migrate in the uterus
until day 15
What is necessary for maternal recognition
migration of the embryo in the uterus
Other than maternal recognition, what other function does embryo migration serve
decreases the chance of twins
What is the usual day of embryo fixation? where does it normally fixate?
day 15-16 at the base of the horn close to the bifurcation
What is the importance of endometrial cups?
they produce eCG which has LH activity causing ovulation and lutenization of follicles, these secondary and accessory CL’s produce progesterone to help maintain pregnancy
Endometrial cups are ____ in origin
fetal
When are endometrial cups active?
day 40-120
An owner calls you stating that her mare aborted at day 60 and she wants to try to rebreed her to still have a chance at her foaling. What is your response
this is not possible because she had already formed endometrial cups and these prevent return to estrus even if the pregnancy is lost
What type of placenta does the mare have
diffuse, microcotyledonary, epitheliochorial
true/false: the entire placental surface is needed for one fetus- twin pregnancies rarely survive
true
True/False: maintenance of pregnancy to term is CL dependent
false
When do all CLs regress by during gestation
day 200
luteal progesterone is necessary to maintain pregnancy until about day ___
80
What is the “to term” gestation length?
320
Before day ____ of gestation the fetus is non viable
300
how do you calculate a mares due date
11 months and 5 days after ovulation
What are two changes in mammary secretions that indicate pending parturition
increase in calcium
drop in pH <6.4
How long does the first stage of labor typically last? what can prolong it?
1-4 hours
human intervention, leave them alone
What is the duration of the second stage of labor?
20min
At what time point does the risk of injury/death to the foal increase rapidly?
30 min
What is the time point that indicates dystocia
> 1hr
How long should it take to expel the placenta?
up to 3hrs post foaling
At what point are fetal membranes considered retained?
after 3 hours
Which two breeds are highly sensitive to retained fetal membranes?
fresian and draft horses
What re the 3 postpartum parameters?
SNP…123
stand by 1 hour
nurse by 2 hours
pass placenta by 3 hours
By what day postpartum should there be no fluid left in the uterine lumen? and by what day should the uterine horns be contracted down to non pregnant size?
15days
30 days
