Exam #3: Repro Pt. 2 Flashcards
When, and with what, do we ideally breed out mares?
> Fresh/cooled semen
- Up to 48 hrs before to 8 hrs after ovulation
- Ideal = 24 hours before ovulation
Old methods = breed every other day from day 4 of estrus (2-3 breedings)
Gold standard method of predicting when to breed?
> Palpation and U/S exam
1) Determine if she’s in heat
2) Examine uterine health
3) Measure follicular size (two measurements, 90 degree angle), measure 2-3 largest follicles at two examinations
4) Examine the cervix
How fast do follicles grow per day?
3 mm/day
What size follicles do mares ovulate?
> 40-45 mm
- Range is 30-50 mm
At what follicular size do we induce ovulation?
When the largest follicle > 35 mm
Two drugs we can use to induce ovulation in the mare
1) hCG
2) Deslorelin acetate (GnRH analog)
Method and time of ovulation with hCG, and sequelae of several uses of hCG
> Acts like LH at the ovary
- Ovulate in 36 +/- 4 hours
*Antibodies will develop after multiple administrations (may not work for ET)
Method and time of ovulation with deslorelin acetate (GnRH analog)
> Mimics the slow LH surge
- IM or implant (remove after ovulation)
- Ovulates in 41 +/- 3 hours
What do you have to keep in mind when you’re trying to manipulate ovulation in the mare?
Some mares will ovulate before 35 mm –> inform your client and continually examine the mare
Ideal sequence of events for induction of ovulation
1) Check the mare - in heat? uterus is healthy?
2) Estimate when she will be > 35 mm
3) Inform the semen collector
4) When the follicle is > 35 mm
a- Confirm semen will be available within 24 hrs
b- Day 0 = give hCG or desorelin
c- Day 1 = breed mare
d- Day 2 = confirm ovulation
Signs you’ve correctly predicted the time of ovulation (3)
1) Follicles slow their growth rate close to ovulation (may not grow 3 mm/day after admin of hCG and deslorelin)
2) Uterine edema may decrease before ovulation
3) Estradiol decreases before ovulation
Things to do post-ovulation (with endometritis and normal mares) (3)
1) Examine endometritis mares 4-6 after breeding = may require uterine lavage, oxytocin if fluid is present
2) Normal mares = examine at ovulation check (24 hrs after breeding)
3) Look for the possibility of a second ovulation = follow the second follicle for 1-2 days (or record them)
When do we inseminate with frozen semen?
> Inseminate 12 hr before to 6 hr after ovulation
- One dose? Examine the mare every 6 hr after induction of ovulation
- More than one dose? Inseminate 24 and 36 hrs after hCG, or 24 and 41 hrs after deslorelin
- Alternative = inseminate at 24 hrs, check for ovulation 36 hrs post-ovulation, inseminate post-ovulation
What do we do if the mare isn’t in heat when we check her the first time this cycle?
- Look at the records
- Confirm the presence of a CL (to ensure she’s not improperly cycling)
- Follow the largest 2-3 follicles
- If she’s really in diestrus = PGF-2-alpha, estrus in 5-7 days, ovulation in 9-11 days
Use of progestins to synchronize estrus
- Used alone or with estradiol (further suppresses FSH)
- Tx for 15 days = allows CL to regress
- Tx for 10 days + PGF
Do we commonly use CIDR’s in mares for estrous synchronization?
No - may induce vaginitis
Are doses of prostaglandins effective for estrus synchronization?
NO = may have two follicular waves
Reasons for estrous suppression (3)
1) Synchronization protocols = breeding and ET
2) Pain/colic during estrus = periovulatory pain (uncommon)
3) Cycle-related behavior or performance problems = MOST COMMON
Treatment of periovulatory pain
1) Induce ovulation
2) Anti-inflammatory tx
Examples of cycle-related behavior or performance problems
- Intense behavioral signs during estrus
- Mare is less cooperative or attentive
- Less tolerance to discomfort = decrease muscular tone and more sensitive
Three main methods of estrous suppression
1) Hormonal
2) Immunological
3) Surgical
Main hormonal drug we use to suppress estrus?
Progesterone - oral, implant, injectable, indirect
Ex: altrenogest oral (SID), injectable P4 in oil, (SID) injectable slow release (every 7-10 days for 2 weeks), injectable altrenogest (every 7-10 days)
How does oxytocin suppress estrus?
Blocks luteolysis - diestrus continues
Given SID/BID 7-14 days post-ovulation
Surgical suppression of estrus
> Ovariectomy
- Permanent
- Risk during surgery
- Requires recovery time
- Doesn’t always solve the problem (decrease estradiol but not progesterone?)
Intrauterine device for estrus suppression
Glass marble - prevents estrus for up to 90 days
- Should be removed when she comes into heat
- Can shatter and lacerate the uterus or other organs
Ideal estrus suppression protocol
- Be sure it’s an estrus problem - not management problem
- Try altrenogest first - if it resolves (continues on a regular cycle), continue it’s use
How old until we start collecting semen from stallions?
20-24 months (any earlier = poor semen quality)
When does sperm production peak in the lifetime of the stallion?
6 years, stays elevated for most of the animals adult life, may decrease in older stallions (> 20 yrs old)
Peak seasonal = May/June
How long does spermatogenesis take?
57 days - any insult will take that long to resolve
Sperm transport takes an additional 7-10 days
Stallion BSE
- Assess mental and physical ability to mate (history, PE)
- Musculoskeletal
- Repro system = internal genitalia (rectal not commonly performed), prepuce/penis, scrotum, libido and sexual stim
- Clean fossa glandis and urethral sinuses
- Do not allow the stallion to mount until the penis is fully erect
- Assess quality and quantity of sperm (collect twice)
- Screen for infectious diseases = culture prepuce, penis, urethral process, ejaculate
What does total scrotal width correlate with?
Sperm production, want them to be > 10 cm
Venereal diseases we screen for
- Contagious equine metritis (USDA oversight)
- Equine viral anemia
- EHV-3
- Dourine
- Pseudomonas aeruginosa
- Klebsiella pneumoniae
Components of semen evaluation
- EVERYTHING SHOULD BE WARM
- Filter and discard gel fraction
- Measure volume
- Assess color - presence of blood, urine?
- Dilute in extender
- Measure total and progressive motility (not just swimming in circles) - 200x in at least 5 fields
- Concentration - hemocytometer (grid estimation) or spectrophotometer
- Morphology w/ staining
- Stain for other cells (Ex: diff quick)
- Others = longevity, pH, dead/live, membrane integrity, acrosome status, mitochondria
Qualities of a satisfactory potential breeder
- Physically sound
- Disease free
- 1 billion motile and normal sperm collected 1 hour after the first ejaculate
How to handle extended semen
Extend semen 1:1, keep at room temp after extender is added
Insemination doses for fresh and cooled semen
> Fresh = 10-30 mL, 250-500 million progressive motile sperm, inseminate within a few hours of collection
Cooled = 1 billion sperm with > 60% motility, inseminate within 24-48 hrs
Quantity of low dose insemination and where we inseminate it
1-20 million progressive motile sperm, at the tip of the horn (uterotubal junction - deep horn with long pipette, hysteroscopic)
What is the number of straws we inseminate with frozen semen?
8 straws = standard dose
Two main reasons we diagnose pregnancy
1) Find the open mares to re-breed
2) Management of twin pregnancies
Behavioral assessment of pregnancy
Anestrus following mating = presumptive pregnancy dx = teast 12, 15, 18, 26 days after estrus, show “teaser cold” and disinterest
False negatives = silent/covert estrus, ineffective teasing, stallion preference
True or false - animals that are pregnant do not show estrus
False - minority of pregnant mares (5-10%) will show estrus
Gold standard of pregnancy diagnosis
Transrectal U/S - finding the embryonic vesicle in the uterine lumen
At what point past conception does the embryo stop moving?
15-16 days post-ovulation, then signals maternal recognition of pregnancy with contact w/ endometrium
What occurs if the embryo isn’t mobile around the uterus?
Release of PGF and luteolysis
Timeline of embryo development during pregnancy diagnosis
- Day 13-15 = motile embryo, dx accuracy is 99%
- Day 21-24 = embryo is present ventrally in the vesicle
- Day 24-26 = viability confirmed w/ heartbeat
- Embryo eventually sits centrally in the vesicle
- Day 45 = organogenesis
- Day 60-70 = fetal sexing
Things to examine on U/S at day 13-15, 21-14, 30, 60-70
> 13-15 = check uterus/ovaries
- No pregnancy = examine 2-3 days
- Single vesicle and CL = examine at 21-24 days (will come back into heat if not preg)
- Single vesicle and two CL = examine 2-3 days (second ovulation)
- Twins = reduce and re-examine in 21-24 days
> Day 21-24
- Single vesicle = examine at day 30
- Twins - deal with immediately
> Day 30 = confirm pregnancy, last change to deal with twins
> Day 60-70 = fetal sexing
When is the cut-off to deal with twins and why?
Day 30 = last chance before endometrial cups form, begin producing hCG (until day 120) and secondary CL’s to maintain the pregnancy
Loses pregnancy after cups form = won’t come back into heat until the cups regress (day 120)
When is the earliest you can palpate to confirm pregnancy with mares?
Day 20-25 (when it’s too late for twins)
Hormone tests for pregnancy diagnosis
- P4 = would be high (highly suggestive if high when she should be in estrus)
- eCG in serum (false + are an issue)
- Estrone sulfate
Hormone patterns during pregnancy (P4, estrogens, eCG)
- Increase and then fall of estrogen = produced by fetal gonads
- CL produces P4, decreases, then saved by endometrial cups eCG, rises with placental P4 production
- Increases in P4 in last month of pregnancy
- eCG = increases and decreases early in pregnancy
Cause of false heats in late pregnancy
Rising E2 and moderate P4 (5 mo of pregnancy) = DON’T BREED
Most common cause of twins in the mare
Double ovulation (not monozygotic or identical)
More commonly bilateral single ovulations than double unilateral ovulations (crowded ovulatory fossa)
Incidence of twins based on breed, repro status, age, etc.
- Breed - high in thoroughbreds, somewhat in quarterhorses
- Repro status = higher in spring/fall, lower in first months post-partum
- Age = higher in older mares
- Significant heritability
Is the mare efficient at reducing twins?
Yes - esp if they’re in the same horn (one twin wins out)
Different horns = may want to reduce it yourself
Why are twins bad? When do probems occur? (3)
- Common cause of fetal mortality = frequently lose one or both fetuses (compete for space and placental exchange)
- Death of one fetus can lead to the abortion of the other
- Twin foals born alive = smaller/weaker, more susceptible to infection, slower to develop, higher rate of stillbirth
- Mares = prone to dystocia and retained fetal membranes, decreased live foaling rates in the following season
Usually occurs between 5-9 mo of gestation when the foals are large in size
Methods of twin reduction
- Pinch
- Manual crushing
- Surgical removal (not great)
- Transvaginal U/S guided aspiration
- Cervical dislocation
