Mare Cycle and Breeding MGMT

Question 1

Where is the transverse fold?

Answer 1

Where the vagina & vestibulum meet…

*REMEMBER*:

• vagina is embryologically derived from
  caudal end/paramesonephric ducts…
• What makes the vestibulum?
  urogenital sinus…
• ​so the PMND & US fuse,
  & that is the site of the transverse fold;
  THE HYMEN!
  🤯🤯🤯

Question 2

What is the perineal body?

Answer 2

Critical role:
helps create a seal b/t vagina & vestibulum

Question 3

What are the 2 major requirements for induction of ovulation in the mare?

Answer 3

Mare must be in estrus w. _>_35mm follicle
95%+ will ovulate in 36-48 hours

Question 4

How is the mare unique in terms of ovulation & LH levels?

Answer 4

Ovulation occurs in response to rising LH;

[LH] actually peaks 2 days after ovulation

Question 5

How would we lengthen the luteal phase in a mare?

Answer 5

Exogenous P₄

negative feedback on hypothalamus & pituitary
⇒suppress LH

suppress signs of estrus but you dont suppress follicular waves
& sometimes you dont suppress ovulation…
⇒does NOT synch ovulation well

Question 6

If you want to synchronize estrus in horses w.P₄ ,
what else do you need to do?

Answer 6

you have to also add E₂…

• the* combination has negative feed back on
• *LH** & FSH → follicular activity stops!

*remove the combo
→brand new set of follicles developing
& fairly predictable ovulation
~10days after stopping treatment*

Question 7

What used to be the standard way to predict when a horse was going to ovulate {pre-ultrasound}?

Answer 7

Tease her to see if she was behaviorally in estrus…
if she was behaviorally in estrus,
then follow the development of follicle
by palpation until it got larger/softer
& then anticipate ovulation in the next 24-48hrs…

Question 8

What’s the “average” pre-ovulatory size of a follicle?

Answer 8

41-42mm

every once in awhile you’ll find a horse that ovulates @ 28mm…
that’s ok, it’s rare…record it

Question 9

How many hours prior to ovulation is the goal to inseminate?

Answer 9

<48hours{maybe even24hrs}
*except frozen semen →breed w/in6hrs*

Question 10

What’s the AI breeding dose for fresh semen? What’s the PR success rate?

Answer 10

500 million PMS
diluted 1:1 with extender
usu. lasts well; 48hrs

~70% PR

Question 11

How is semen packaged for cryopreservation?

Answer 11

• 0.5 mL straws
  
  • {designed to have inseminating dose of 8 straws}
  • → 4mL @ 200-250 x 10⁶ sperm per mL
• 800 million total sperm
• min.progressively motility: >30% after thawing
  
  • → 240 x10⁶ {240 million progressively motile sperm=optimal}

Question 12

What’s the most common ovarian tumor?

Answer 12

Granulosa/Theca cell tumor
They always start at ovulation fossa;
before ovary gets large, tumor defaces this structure…

Question 13

During teasing, what grade of the mare will she accept/stand for the stallion?

Answer 13

Grade 3

Question 14

What would we see behaviorally in the mare at a grade 4 estrus?

Answer 14

“Winking”

Question 15

The picture below is an ultrasound of a pregnant mare. What stage of gestation is she in?

Answer 15

18 days w.fixed embryo

Question 16

Upon palpation, you detect a tight cervix & ​toned uterus…what stage of the estrous cycle is the mare in?

Answer 16

Diestrus

vaginal speculum exam appears as “rose bud”
*cervix would beclosed; pale pink, dry, &elevated off the vaginal floor*

Question 17

What 2 prostaglandins can be administered >5 days post-ovulation to shorten the luteal phase?

Answer 17

1. Dinoprost {Lutalyse}
2. Cloprostenol {Estrumate}

Question 18

What is the time frame post-fertilization in the mare that the embryo will enter the uterus?

Answer 18

5-6 days

Question 19

What’s the drug of choice to attempt to treat the mare if she rejects the foal?

Answer 19

Reserpine