Flashcards in Reproductive Anatomy & Physiology of the Mare Deck (66):
The cervix in the mare is approximately how long?
What is the most sensitive organ to hormonal stimulation in the mare?
The cervix in the mare is closed and dry under the influence of what hormone?
The cervix in the mare is low, relaxed and moist under the influence of what hormone?
Are ovaries located more laterally in the cow or mare?
What shape is the uterus of the mare?
Y or T shaped
What attaches the reproductive tract to the abdominal wall and may make the ovaries difficult to locate?
2 broad ligaments
The extensive mesovarium in a mare can mean what?
Wide variation in ovarian position
The uterus has about how many folds that run from the tip of the horns to the cervix?
What do these aid in?
- 12-14 folds
- Fluid evacuation
What are 3 functions of the oviduct?
- Sperm storage
- Fertilization site
- Embryo transport
Unfertilized ova are retained where?
Fertilized ova (embryos) descend to where?
- 5.5 days after fertilization
The UTJ opens in response to what?
The ovaries in the mare tend to be around what vertebrae?
3rd or 4th lumbar vertebrae
Where is the site of ovulation on the ovary of a mare?
Mature follicles are what size?
The further away from the ovulation fossa the oocyte is, the more dramatic the what?
Follicular change in shape (follicle oblongation)
The mare's udder has how many halves?
Each half has how many glands?
- 2 halves
- 2 glands
How many orifices are in each teat in the mare?
Regulation of the reproductive cycle of the mare is governed by what?
The majority of mares show signs of heat during what months?
May to August
Mares that have little to no ovarian activity and the uterus is flaccid with no tone are in what part of the cycle?
Short days stimulate what in the mare?
Stimulate the pineal gland to release melatonin that inhibits GnRH production.
How long is artificial lighting set for?
16 hours of light and 8 hours of dark
What size light bulb should be used for artificial lighting in a 12 x 12 stall?
What is artificial lighting used for?
Advances transitional phase
What hormone can be used during seasonal anestrous to bring the mare out of anestrous?
- 20-25 ug TID IM for 2-3 weeks
T/F: During the transitional phase, mares have multiple, variable size follicles.
How does the uterus appear during the transitional phase in a mare?
Uterus has estrual tone with evidence of uterine edema.
When does the transitional phase in a mare end?
With the first ovulation of the year.
What dose of progesterone can be given to reduce the length of the transitional period in a mare?
150 mg IM SID for 10 days
What dose of progestogens (Altrenogest) can be given to reduce the length of the transitional period in a mare?
0.044 mg/kg PO SID for 10 days
What are 2 examples of dopamine antagonists that can be used to reduce the length of the transitional period in mares?
- Domperidone (PO)
- Sulpiride (IM)
Behavioral estrus is a result of estrogen acting on what receptors?
Alpha receptors of the brain
T/F: The sensitivity of estrogen is the same between mares.
False - The sensitivity of estrogen is VARIABLE between mares.
Is behavioral estrus a reliable breeding management tool to use in mares?
During physiologic estrus, the mare is under the influence of what hormone?
There is up regulation and activation of what type of receptors during physiologic estrus?
Follicular LH receptors
Circulating estrogen levels are important for up regulation of what receptors?
Physiologic estrus starts around what day if ovulation is day 0?
What is the normal inter-ovulatory interval in a mare?
What are 3 methods of estrus detection in the mare?
- Rectal palpation/vaginoscopy
What are 4 observations made with rectal palpation/vaginoscopy during estrus?
- Hyperemic moist elongated vulva
- Soft cervix
- Turgid uterus
- Presence of a follicle
What are 2 observations made using US during estrus?
- Hyperplasia/edema of uterine folds
- Large dominant follicle
At any stage during diestrus in the mare, an ovary may contain what?
Antral follicles of less than 2 to greater than 35 mm in diameter at different stages of growth and regression.
The major primary wave starts with what?
Finishes with what?
- Starts with uterine PGF
- Finishes with ovulation
To distinguish between growing and regressing follicles of the ovulatory wave, what is necessary?
More than one US exam.
What is a key component for proper breeding management?
Manipulation of the estrous cycle
How large must a follicle be in order to be able to induce ovulation?
Greater than 35 mm
What must be present in the uterus to induce ovulation?
What are 2 components of this?
- Uterine edema
- Estrogen exposure and LH receptors
When does ovulation usually occur once induced?
What are 4 examples of ovulation induction hormones?
- Human chorionic gonadotropin (hCG)
- Deslorelin injectable (Sucromate)
- Deslorelin pellet (Ovuplant)
- Recombinant LH (rLH)
When does ovulation occur when induced by Ovuplant?
What is a drug that is very effective to induce ovulation in mares with good edema and a dominant follicle (35-42 mm)?
What is a good choice for ovulation induction with fixed time insemination programs with cooled and/or frozen semen?
What are 2 advantages of using Deslorelin vs hCG to induce ovulation in a mare?
- Highly effective
- Wider window for treatment
What are 3 possible causes of failure to respond to ovulatory inducing agents?
- "Immature follicles" (not enough LH receptors)
- Mare not in estrus even though large follicle is present
- Anovulatory follicles (AHF)
What are 4 criteria to determine whether or not a CL is present on US?
- Volume/area of the CL
- Luteal tissue echogenicity
- Doppler showing vascularization of CL
T/F: The US appearance of the CL is a good indicator of its functionality and its age.
False - It is NOT a good indicator of functionality or age.
What are 5 possible indications that an anovulatory follicle (AHF/HAF) is present?
- Fails to ovulate in response to ovulatory inducing agents
- Increases in size beyond normal
- numerous free-floating echoic specks in the antrum
- Single fibrin tags floating in FF
- Organized fibrin in antrum
What are 2 estrus induction agents that are luteolytic?
- Prostaglandin F2 alpha (Lutalyse)
- Cloprostenol (Estrumate)
When progesterone levels from to what level in what amount of time, this induces estrus?
Less than 1 ng/mL in about 24 hours
A CL must be how many days old in order to be fully responsive to prostaglandin?
5 days old
It is suggested to examine mares when in order to better predict the PGF response?
At the time of treatment.
What are 2 things prostaglandins should not be used for?
- Ovulation induction
- Uterine evacuation post-ovulation