Mare Reproductive Physiology

Question 1

Clitoris of the mare

is embedded in ______ where there are sinuses located

Answer 1

clitoral fossa

Question 2

Vestibulum separated from vagina by the ________

the SECOND barrier of bacterial contamination

Answer 2

vestibule vaginal seal

Question 3

____ artery can cause severe hemorrhage when foaling

Answer 3

Uterine

Question 4

Ovaries suspended high up in paralumbar fossa

by the _______ ligaments

Answer 4

broad

Question 5

The _____ is ~ 10-15cm in length and is

the most sensitive organ of hormonal stimulation

in the mare; the 3rd and last barrier for bacterial contamination

Answer 5

Cervix

Question 6

Cervix is always dilatable in mare due to absence of ________

Answer 6

fibrous rings

Question 7

The cervix is very tight, prominent and easy to palpate under the influence of _______

Answer 7

progesterone

Question 8

The cervix is low relaxed and moist under the influence of _______

Answer 8

estrogen

Question 9

_______ and ________ are external reproductive organs

in the mare

Answer 9

Vulva and clitoris

Question 10

The _________ is the site of

sperm storage, fertilization, and embryo transport

in the mare

Answer 10

Oviduct

Question 11

The opening of the uterotubual junction opens

in response to ____

produced by the embryo.

If mare is not bred/oocyte not fertilized,

uterotubal junction will NOT open and unfertilized eggs will NOT come into the uterus

Answer 11

PGE (prostaglandin

Question 12

Unfertilized ova retained in the ______ – NOT in uterus

Answer 12

oviduct

Question 13

_________ of the ovaries is the site of ovulation

Answer 13

Ovulation fossa

Question 14

Mare udders have 2 halves and each

half has ____ glands with 1 orifice each

Answer 14

2 glands

Question 15

Horses are ________ breeders

_____ days stimulate the pineal gland to release melatonin that inhibits GnRH

Answer 15

seasonal LONG-day breeders

short days stimulate the pineal gland to release melatonin that inhibits GnRH

Question 16

Mares are in anestrous during this season, but can

be induced to ovulate using artificial light

Answer 16

Winter

Question 17

What do you give to make a mare fall back into anestrous?

Answer 17

• GnRH 20-25 ugs TID IM 2-3w

Question 18

Which drugs can be given to horses to

reduce the length of the transitional period (spring and fall)?

Answer 18

Progesterone

Progestagens (ALTRENOGEST)

Dopamine antagonists (DOMPERIDONE, SULPIRIDE)

Question 19

FSH from the pituitary gland is produced in _____ phase,

meaning that at any time of the cycle, even during diestrus,

the mare will have FSH production

Answer 19

bimodal

Question 20

Because the mare is always producing FSH,

they grow ______ at anytime during their cycle

Answer 20

follicles

Question 21

In cow, high levels of estrogen give + feedback to simulate

this will allow for spike of LH

How is this different from the mare?

Answer 21

Mare: High levels of estrogen stimulate LH production

BUT has a very protracted increase of LH (does not spike),

may peak after ovulation

Question 22

_________ is secreted by CL and

will reach high levels for 13-15 d

Answer 22

PROGESTERONE

Question 23

What do you expect to see on an US

of a mare in estrus?

Answer 23

Hyperplasia/edema of uterine folds

Large dominant follicle

Question 24

What do you expect to find on rectal palpation

and vaginoscopy of a mare in estrus?

Answer 24

Hyperemic moist elongated vulva

Soft cervix

Turgid (swollen, congested) uterus

Presence of a follicle

Question 25

INTERESTRUS INTERVAL IS _____ days; INTEROVULATORY PERIOD IS ____ days

Answer 25

Interestrus interval = **15 days** Interovulatory interval = **21 days**

Question 26

Mares are in heat for ____ days and show heat ______ hours after ovulation

Answer 26

4 - 5 days 24 - 48 hours after ovulation

Question 27

Which hormones can be used to induce ovulation in mares?

Answer 27

Human Chorionic Gonadotropin (hCG) DESLORELIN INJECTABLE (SUCROMATE) DESLORELIN PELLET (OVUPLANT) RECOMBINANT LH (RLH)

Question 28

What are the advantages of Deslorelin over hCG in inducing ovulation?

Answer 28

Highly effective • Wider window for treatment

Question 29

What are the ultrasonographic signs of ovulation in the mare?

Answer 29

Decreased turgidity * Loss of spherical shape * Apical area * Echoic spots in antrum * Serration of granulosa * EDEMA OF GRANULOSA CELL LAYER AND SERRATION (wrinkling) of granulosa cell layer.

Question 30

What is the last thing you see on ultrasound before a mare ovulates?

Answer 30

Last thing you see is: EDEMA OF GRANULOSA CELL LAYER AND SERRATION (wrinkling) of granulosa cell layer. At this point, she is **2-4 hours away** from ovulating

Question 31

**IMPORTANT QUESTION!** **To induce ovulation of a mid-diestrus follicle of 40mm** **in diameter, we can use:** A: 2500 IU hCG B: 1.5 mg Deslorelin C: Luteolytic dose of Prostaglandin D: All the above E: None of the above

Answer 31

E: None of the above!!!!!! If this was a mid-ESTRUS follicle, A or B would be correct!

Question 32

Anovulatory Hemorrhagic Follicles (AHF) can cause a mare to fail to respond to \_\_\_\_\_\_\_\_\_\_ agents

Answer 32

ovulatory inducing

Question 33

How is estrus induced in the mare?

Answer 33

Luteolysis using: PROSTAGLANDIN _PGF2a_ (**Lutalyse** 5mgs IM/SQ) _CLOPROSTENOL_ (**Estrumate** 250ugs IM/SQ)

Question 34

What is the difference in PGF2a and Cloprostenol luteolytics in induction of estrus?

Answer 34

The diff between them is PGF2a is natural and Cloprostenol is an analog. Big difference in half-life. PGF2a is metabolized in the first passage.

Question 35

CL must be \_\_\_\_\_\_days old to fully respond to prostaglandin

Answer 35

5 days old

Question 36

**IMPORTANT QUESTION:** The interval between prostaglandin injection and ovulation is determined by the size of the follicle at the time of treatment: T/F?

Answer 36

TRUE

Question 37

**IMPORTANT QUESTION:** T/F:

Answer 37

TRUE * A mare that is in TRANSITIONAL PHASE* * (multiple medium follicles, showing heat for a long time,* * upper midwest, middle of march) should get* * REGUMATE or PROGESTAGEN for 10 days!*

Question 38

T/F: Prostaglandins are effective in inducing ovulation, uterine evacuation post-ovulation, and inducing parturition

Answer 38

**FALSE!! These are all WRONG uses for Prostaglandin (PG)** * Ovulation induction: some people think it does this BUT it happens because she has a follicle ready* * Uterine evacuation post-ovulation: PG has an effect to contract smooth mm and aids in uterine evacuation but PG also has anti-luteogenic effect so we do not use it POST OVULATION for uterine evacuation* * Induction of parturition: when you treat a mare with PG to induce foaling, it could be VERY explosive and lead to ruptured cervixes or fx ribs*