Reproductive Anatomy & Physiology of the Mare (meh, mostly done) Flashcards
The most reliable hormone to induce ovulation in the mare is:
Deslorelin
- GnRH analogue; Induces ovulation within 38-42 hours (90%)
- Very effective in mares with good edema and a dominant follicle (35-42 mm)
The cervix in the mare is about ________cm in length and is the most sensitive organ to hormonal stimulation
The cervix in the mare is about 10-15 cm in length and is the most sensitive organ to hormonal stimulation
- Closed, dry under the influence of progesterone
- Low relaxed and moist under the influence of estrogen
- Cervix is always dilatable in mare due to absence of fibrous rings
The most accurate way to determine heat in mares is:
Endometrial edema and a dominant follicle on ultrasound
T/F: The interval between prostaglandin injection and ovulation is determined by the size of the follicle at the time of treatment.
True
What is most commonly administered to reduce the length of the transitional period in mares?
- Progesterone
- Synthetic progestins (Altrenogest)
Regulation of the reproductive cycle of the mare is governed by the _____________ axis.
Hypothalamic-Pituitary-Gonadal (HPG)
- The HPG axis must be properly “charged and fined tuned” for the system to work properly
- With the appropriate use of exogenous products the HPG axis can be stimulated, stabilized and/or synchronized
- However, the system can also be de-stabilized with the inappropriate or the untimely used of exogenous hormones.
The period between ovulation associated with estrus and ovulation associated with the next estrus is termed __________
interovulatory interval
Once the mare has had the first ovulation of the year, the inter ovulatory interval is on the average 19–22 days
The __________ in the mare is a site for fertilization and sperm storage
oviduct
Any unfertilized oocytes will not fall into the uterus. They will be retained in the oviduct and can actually block/inspissate in the oviduct.
The uterus in the mare has ________ folds that run from the tip of the horns to the cervix and aid in __________
The uterus in the mare has 12-14 folds that run from the tip of the horns to the cervix and aid in fluid evacuation
The uterotubular junction (UTJ) in the mare opens in response to:
PGE
Prostaglandin E
Mares in Winter anestrous:
- Never show heat
- Rarely show heat
- About 30% show heat but only half ovulate
- Often show heat but never ovulate
About 30% show heat but only half ovulate
__________ is the site of ovulation in the mare
Ovulation fossa
Ovulation induction hormones in the mare include:
-
Human chorionic gonadotropin (hCG)
- 70% ovulate within 24-48 hours
-
Deslorelin (Sucromate®)
- 90%+ ovulate between 38-44 hours
- GnRH analogue - results in the release of FSH and LH
- Recombinant LH (rLH)
The opening of the oviduct in the mare is called the:
uterotubular junction (UTJ)
Which of the following have been indicated in hastening the time to 1st transitional season ovulation in the mare?
- Increasing light
- Sulpiride
- Domperidone
- All of the above
All of the above
- Domperidone and Sulpiride are dopamine antagonists.*
- Light is light.*
To induce ovulation of a mid-diestrus follicle of 40 mm in diameter we can use:
- 2500 IU of hCG
- 1.5 mg deslorelin
- Luteolytic dose of prostaglandin
- All of the above
- None of the above
1.5 mg Deslorelin
The reproductive barriers for bacterial defense in the mare are:
- Vulva
- Vestibulo-vaginal seal
- Cervix
Behavioral estrus is attributed to the effects of increasing circulating concentrations of __________
estrogen
Estradiol of follicular origin is the predominant reproductive steroid in the blood at the beginning of estrus. Progesterone is low at this time (less than 1ng/ml), and mares should begin to show behavioral signs of estrus when teased (eversion of the clitoris, frequent urination, standing for the stallion, etc.).
When are you most likely to see numerous anovulatory follicles in a mare?
- Fall transition
- Spring Transition
- Summer solstice
- A & B
- A & C
A & B
Fall transition & Spring Transition
What are the general requirements for induction of ovulation in the mare?
- Follicle size (>35 mm breed effect)
- Uterine edema (estrogen exposure and LH receptors)
-
Ovulation should occur 24-48 hours after treatment
- Average 36-44 hours (80%)
The most likely cause for a mare to fail to respond to an ovulatory inducing agent:
- “Immature follicles”
- Mares are not in estrus even though a large follicle is present
- Anovulatory Follicles (AHF)
- All of the above
All of the above
It is the middle of march in the upper mid-west. A 5 year old maiden mare has been showing heat to a gelding for 10 days. On palpation and US exam she has multiple 20-25 mm follicles on both ovaries and marked uterine edema.
T/F: The most effective way to promote the development of a preovulatory size follicle is to give the mare a progestagen such as altrenogest (Regumate) for 10 consecutive days.
True
The most effective way to synchronize the ovulations of 2 mares is by:
- Giving PGF on day 5 post ovulation to both
- Giving progesterone for 10 days and then PGF
- Using PGF and deslorelin judiciously
- All of the above
- None of the above
Giving progesterone for 10 days and then PGF
Oral administration of altrenogest for 10 days with an injection of PGF2a the last day result in most mares exhibiting estrus in 2 to 5 days after withdrawal.
T/F: The cervix is always dilatable in the mare due to absence of fibrous rings
True
Once the mare has had the first ovulation of the year, the inter ovulatory interval is on the average ________ days.
19-22 days
T/F: In the mare, the cervix closes under the influence of progesterone.
True
The cervix closes under the influence of progesterone. It relaxes (to a variable degree) during the estrous cycle when serum progesterone is low, by becoming shorter and wider from the beginning of estrus up until the time of ovulation, after which time it again closes.
The predominant reproductive hormone during the diestrus period in the mare is __________
progesterone
Blood levels of progesterone increase rapidly following ovulation, reaching a maximum (greater than 4ng/ml) 4 to 7 days after ovulation
