Lecture 5 Flashcards
What affects pregnancy rates in the mare
Breeding management
Stallion fertility
Mare fertility
Early pregnancy detection (twins and early embryonic death)
What history do we need to know about the mare?
Fertility history
Foaling history
Type of breeding program
BSE
How long is the mares estrus
4-7 days
What determines whether the estrus length is short or long?
Day length! Horses are seasonally polyestrus
Longer days (June/july) results in a shorter estrus period
How long is diestrus?
14-16 days
Independent of day length
What would shorten diestrus?
Lengthen it?
Abnormal conditions of the uterus (inflammation releases prostaglandin which lyses CL)
Pregnancy or prolonged CL
How does a mare act if she’s in estrus and exposed to a stallion?
Estrogen influence:
Tail goes up
Urination
“Wink” (clitoral eversion)
How does a mare act to a stallion if she is in diestrus?
Progesterone influence:
Ears back, striking or kicking
What can you see/feel with transrectal palpation and US
Ovaries- follicular development
Uterus- tone and edema
Cervix- tone/relaxation
What causes the cervix to be relaxed?
Toned?
Relaxed/short/edematous during estrus
toned/long/tight/tubular during diestrus
What is unique about mare’s ovarian structure? How does this affect ovulation?
It is inside out which means she can only ovulate out of one spot (ovulation fossa)
Can you feel a CL in horses? What about cows?
No in horses, yes in cows
What is short cycling?
Give prostaglandin to lyse the C.L. And bring the mare from distestrus to estrus
When can you use PGF2alpha to lyse the CL?
No earlier than 5 days post-ovulation
When will onset of estrus occur after administration of PGF2alpha?
5-7 days on average..will depend on follicular activity
What do we use to predict ovulation?
Follicular size (greater than or equal to 35 mm) Follicular texture (softer and more fluid filled) Follicular shape (irregular) Uterine edema
What is deslorelin acetate?
Who does it work on?
GnRH analog
Ovulatory agent
Works on mares already showing estrus with estrus edema and relaxed cervix
What size follicle do you need to use deslorelin acetate?
Greater than or equal to 30 mm
When will ovulation happen post administration of deslorelin acetate
40-48 hours (44 hours)
How does deslorelin acetate work?
Works on pituitary to release more LH and FSH
What is hCG?
What does it do?
What mares can it be used on?
ovulatory agent
Acts as an LH analog and works directly on the follicle
Can be used on mares with estrus edema and relaxed cervix
What size follicle do you need in order to administer hCG?
How long until the mare will ovulate after administering hCG?
Greater than or equal to 35 mm
24-48 hours (36 hours)
When do you want to breed?
As close to ovulation as possible!!
How long does the oocyte live after ovulation?
24 hours but is only truly viable for the first 12 hours post ovulation
How long can sperm live in the mare?
Fresh semen: 48+ hours
Chilled semen: 24-48 hours
Frozen semen: 12 hours post thaw
*can possibly live up to 7 days
When you inseminate with fresh semen, how much do you need?
Minimum of 500 million progressively motile sperm
How often do you inseminate with fresh semen?
Every other day because you’re assuming the semen lives in the tract for 48 hours
What is the most common method of insemination?
AI with fresh cooled semen
Once the semen is shipped, how long does it take to get to you?
24 hours
What minimum semen are you sent with fresh cooled semen?
Two doses of 1 billion progressively motile sperm
What is the conservative approach to timed AI with cooled semen?
- Seen mare is ready for breeding
- Call for semen
- give first dose of AI and dose of hCG
- next day, give second dose of AI as long as she hasn’t ovulated
- 36 hours post hCG mare should ovulate
What is the daredevil approach to timed AI with cooled semen?
- see mare is ready for breeding
- call for semen and give hCG
- give both doses of semen 24 hours later
Always check semen before ? For ?
Insemination for motility and morphology
When should do a pregnancy exam?
14 days post ovulation
*look for twins
