Mare Reproduction Flashcards
What are some demands placed on an equine theriogenologist?
seasonal breeding patterns of mares, commercial emphasis on early born foals, breeding during ventral transition, managing the stallion book, breed registry requirements
What is the central control of reproductive anatomy controlled by?
hypothalamus, pituitary, and pineal gland
What is the structure of the ovary in the mare?
reverse cortical to medullary arrangement meaning the medulla is on the outside except at the ovulation fossa
Where are the ovaries located in the mare?
caudal to the kidneys
True or false: Follicles stop growing during pregancy in the mare.
False, there is significant follicular growth during pregnancy
What are some common ovarian abnormalities in the mare?
hemorrhagic anvulatory follicles and granulosa theca cell tumors
How do hemorrhagic anovulatory follicles form?
the mare grows a large follicle but does not ovulate and fills with blood
When do hemorrhagic anovulatory follicles happen most often?
when changing out of breeding season into anestrus
What are the structures of the uterine tube?
infundibulum, ampulla, and isthmus
What is the infundibulum?
a structure that covers the ovulation fossa to try and catch the oocyte
What is the ampulla?
the longest portion of the uterine tubes that is plicated and the site for fertilization
What is the function of the ciliated epithelium in the ampulla?
it propels the oocyte down the ampulla
What is the isthmus?
a sperm reservoir
What do the utero-tubal papilla in the uterine tubes allow for?
one way traffic
What clinical issue can occur in the uterine tubes?
oviductal blockage by an oocyte that can lead to inflammation
What type of uterus does the mare have?
simple, bicornate uterus
What is the size of the uterus based on?
physiology and parity - gestation and seasonal influences
What is the purpose of the corpus cornual junction and where is it located?
the base of the horns for implantation embryo fixation
What does uterine flaccidity lead to?
edema which leads to estrus
What stimulates uterine tone?
progesterone
What clinical issue is associated with the uterus?
endometritis and uterine fluid acumulation
What part of the uterus can be used as an indicator of uterine health?
glandular endometrium
What is an important barrier in the mare repro tract?
the cervix
What type of folds does the cervix have?
longitudinal
How does the cervix respond to hormones?
it increases its collagen and connective tissue
What does the glandular epithelium of the cervix produce?
copious mucous
What can trauma to the cervix cause?
infertility/pregnancy loss
What does the vagina start and end?
from the fornix to the labia
Is the equine vagina glandular or aglandular?
aglandular
Upon exposure to air, what can happen to the mares vagina?
it becomes hyperemic
What clinical issues are associated with the mares vagina?
vaginal trauma, vestibular trauma, varicose veins, and fistulas
What are the three barriers of infection in the mare’s repro tract?
cervix, vestibule, and vulva
What happens when the vestibule is not a full ring?
a pneumovagina
What type of tissue is the vulva?
elastic tissue
What does dorsal displacement of the vulva lead to?
loss of barrier which leads to pneumovagina which leads to fecal contamination
What is the clitoris homologous to in the stallion?
the penis
Where does bacteria tend to accumulate in the mare?
in the clitoral siinuses
What is a sign from the clitoris that a mare is in estrus?
winking
What type of breeders are mares?
long day polyestrous breeders
What is the natural breeding season for horse mares?
april to september/october
What is the natural breeding season for pony mares?
may to september/octover
When does puberty usually occur in the mare?
around 15 months of age
What is puberty described as?
age of first estrus, age of first ovulation, and age at which the female can support pregnancy without deleterious effects
What are the hormone trends that lead to cyclicity and ovulation?
decrease in sensitivity to low E2, increase in GnRH to increase in FSH to increase in E to a surge of LH which leads to ovulation
What factors influence puberty?
body size (fat), environmental cues (season of birth and photoperiod), and social cues from other females
What is the length of the estrous cycle in mares?
19-22 days
What are the hormone trends during estrus?
increased estradiol, decreased progesterone, then decreased FSH and increased LH
How long does estrus usually last?
4.5-8.9 days (mean 6.5 days)
When does ovulation occur?
24-48 hours before the end of estrus
What does the dominant follicle in estrus produce?
E2 and inhibin
What does multiple ovulations in an estrus cycle usually lead to?
twins
What are some examples of abnormal estrous behavior?
seasonal transition and ovarian tumors
What are some behavioral signs of estrus?
peeing, raising tail, clitoral winking, and squatting
Aside from behavioral signs, what are some other methods of detecting estrus?
trans-rectal palpation of the reproductive tract and ultrasound examination of the preproductive tract, and hormone estimations
What hormone is usually used to detect estrus?
progesterone
What is the progesterone dominant phaase?
the luteal phase
What happens to P4 serum concentration after ovulation?
it rises rapidly (peak 8-16 ng/ml)
How many follicular waves occur during diestrus?
one to two
What is the corpus luteum sensitive to after day for of diestrus?
PGF2 alpha
What structure cannot be palpated in mares?
the corpus luteum
What are some ways to manipulate the estrous cycle?
inducing early cyclicity, ovulation, CL regression/luteolysis or prolonging the luteal phase and sudden withdrawal
How is early cyclicity induced?
photoperiod and pharmacological manipulation (domperidone and sulpiride)
How is ovulation induced?
using a GnRH agonist (desloredin) or an LH agonist (HCG)
How is CL regression/luteolysis induced?
prostaglandin analogues (dinoprost tromethamine, cloprostenol)
How is the luteal phase and sudden withdrawal induced?
progesterone compounds
What are some behaviors/events of early conceptus/embryo?
early transport through the oviduct (PGE production), mobility of the equine embryo (production of PGs), formation of a glycoprotein capsule, and maternal recognition of pregnancy signal
What are events that happen in a pregnant mare post fixation?
fixation at the corpus-cornual junction, orientation of the embryo, shedding/loss of the capsule, embryonic development (amnion, allantois, yolk sac), and a visible heart beat
When is the heart beat visible?
by day 22-23
Where do unicornuate twin conceptuses fix and when?
on the ventral aspect of the base of the uterine horne at 26 days of gestation
What is the first step of endometiral cup formation?
trophopblast invades from the chorionic girdle at 30-35 days
What hormone is produced during endometrial cup formation?
eCG
What is the purpose of eCG?
it is for pregnancy maintenance, it is like LH
When does endometrial cup formation peak?
at 55-60 days
When does endometrial cup formation decline?
after 120-150 days of gestation
What are some clinical issues associated with endometrial cup formation?
embryo/fetal loss after endometrial cup formation and retained endometrial cups
After ovulation what happens to progesterone?
it increases rapidly and then decreases
Without eCG what happens to progesterone levels after ovulation?
it will continue to decrease and the pregnancy will terminate
What influence does eCG have on progesterone levels?
the primary corpus luteum is stimulated and P4 increases, as eCG continues to increase, accessory CL develops and P4 increases until about day 100
After day 100 of pregnancy, what structure assumes the role of P4 production?
the placenta
Aside from progesterone, what other hormones are associated with pregnancy?
estrogens and their conjugates, relaxin, oxytocin, glucocorticoids, prolactin and growth hoormone, and fetal hormones
When is relaxin released during pregnancy?
near to parturition for relaxing the cervix
What is the function in glucocorticoids in pregnancy?
it initiates parturition
What is the function of prolatin and growth hormone in mares?
for mammary development
What fetal hormones are a factor in pregnancy?
steroids, P4 and E2 precursors, insulin, T3, and T4
What hormone is not present in mares that is present in most other species?
placental lactogen
How long does it take for placentation to occur?
slowly - can take up to 150 days
What type of placentation of occurs in mares?
epitheliochorial, diffuse placentation
What is diffuse placentation?
when the placenta attaches to every part of the uterus
What type of organ is the placenta in the mare?
an endocrine organ
What is the function of the placenta?
to protect the fetus from the immune system of the mare and secretes growth factors and nutrients
When does the placenta need to come out?
immediately after parturition
How long does gestation usually take in mares?
330 - 365+ days
Why is induction of parturition unpopular?
because the fetus matures late
The ____ determines the day of parturition, the _____ determines the hour.
fetus, mare
What is the first stage of labor and how long does it take?
fetal positioning (30 minutes to hours)
What is the seond stage of labor and how long does it take?
expulsion of the fetus (20-30 minutes)
What is the third stage of labor and how long does it take?
expulsion of the placenta (15 minutes to 3 hours)
What are the three post partum events that a mare goes through?
rapid expulsion of the placenta, involution of the uterus, and return to estrus
What is ‘foal heat’?
the first estrus cycle after foaling - usually 7 days after foaling
When will we breed a mare during her ‘foal heat’?
If she did not have a dystocia, there was not a retained fetal membrane, and if she is not over 12 years of age
