equine 1 Flashcards
horses have what kind of estrous cycle?
seasonal, polyestrous, long day breeders
how long is the mare’s estrous cycle?
21 days, although estrus duration varies with season (avg 7 days)
ovulation occurs ______ days ____(before/after) behavioural estrus ends.
1-2 days before
when is the mare’s breeding season?
summer (may-aug)
transition periods in the mare occur when?
fall and spring
what is transition in the mare?
period of time when ovaries transition between estrus and anestrus
may see behaviour signs of estrus and stallion receptivity
not usually correlated with ovulations
why are transition periods in the mare clinically important?
- unusable to be bred during these times; can delay breeding
- mare behaviour can be problematic for owners
mares have ___ follicular waves and ovulation occurs during ____.
2, estrus
most mares will ovulate a follicule between _____ (size) _____ (time) before the end of estrus.
40-50mm
24-48 h
mares show signs of heat _____ after ovulation
48 hours
follicle size and length of estrus vary considerably between individuals, breed, age, season, access to teasing, etc. BUT follicles typically grow ____ per day during estrus. why is this important to know?
3-5mm/day
give you a baseline for tracking
tell me some estrus activity in the mare
- squealing
- excess urinating (small streams)
- winking
- tail raising
- posturing with wide hind legs
- back pain
- grumpy or cuddly
- sensitivity to work
- lack of focus
- no signs at all
basically, it’s unpredictable!
melatonin ___ with increasing day light
decreases
what is the #1 most important controller of seasonal polyestrous breeders?
melatonin
tell me how melatonin controls seasonal polyestrous breeders
- increased light
- decreased melatonin
- stimulation of GnRH in the hypothalamus
- stimulation of the pituitary gland to produce further hormones (FSH & LH)
GnRH is released from where?
hypothalamus
what does GnRH do?
stimulates the pituitary gland (pars distils), which produces gonadotropins (FHS & LH)
FSH is produced in the ___ in response to ____. what does it do?
pituitary gland, GnRH
- pushes mares out of transition in the spring
- stimulates follicular growth
- stimulates granulosa cell development
there are ___ waves of FSH through the mare’s cycle. when are they?
2
during diestrus (once at the start and once at the end)
different from other animals
why does FSH peak twice during diestrus?
allows for 1-2 waves of follicular development
selection for 1 follicle to be dominant – don’t want twins!
inhibin is produced _____.
in the granulosa cells of the dominant follicle
what does inhibin do?
serves as a (-) feedback loop to the pituitary gland
inhibits FSH so no other follicles develop
(a method of self-selection ensuring one follicle develops)
estrogen is produced by ____, when?
mature follicles, nearing estrus (20-25mm)
what does estrogen do?
- stimulates behavioural response in the brain
- estrus activity
- relaxes cervix
- increases smooth muscle activity in the uterus to prepare to transport sperm
- stimulates the pituitary gland to reduce FSH production and increase LH production
- increases edema of the uterus, vagina, and vulvar lips
uterine edema is at its max when?
24 hours before ovulation
tell me what’s going on in these ultrasound pictures.
from L to R, going from no edema to lots of uterine edema (estrus)
LH is produced in the _____. what does it do?
- pituitary gland
- facilitates maturation of the dominant follicle (prepares to ovulate)
LH peaks when?
2 days post ovulation in the mare
different from other animals
LH surge can be influenced by…?
teasing/stallion contact
LH only works on what kind of follicles?
mature follicles greater than 35 mm (they have the LH receptors)
LH signifies the beginning of what?
luteal phase
CH forms in the ovulation fossa which matures to a CL
CL controls diestrus or pregnancy
progesterone is primarily produced by ____
the CL
progesterone ____ after ovulation
increases
what does progesterone do?
- acts to inhibit further estrus stimulating hormones (FSH & LH)
- prepares uterus for pregnancy (reduces contractility to smooth muscle in uterus, stimulates tightening/contraction of cervix)
what does progesterone do during diestrus? what about during pregnancy?
remains high for both
if the mare is not pregnant after ovulating, what does the lining of the endometrium produce?
prostaglandin (PGF2 alpha)
what does PGF2 alpha do?
destroys the CL, thus reducing the amount of progesterone
allows for another cycle of FSH to begin
tell me what the sex hormones are doing during a mare’s cycle (estrogen, progesterone, LH, FSH)
estrus:
- estrogen peaks
- LH rises
- progesterone low
- FSH low
diestrus:
- FSH peaks twice
- estrogen low
- progesterone peaks + plateaus for all of diestrus
- LH peaks 1-2 days after ovulation (1-2 days into diestrus), then is low
tell me what the hormones are doing during spring transition in the mare
- decrease melatonin
- increase GnRH
- increase FSH
irregular heats w/o ovulation
tell me what the hormones are doing during the breeding season in the mare
- decrease melatonin
- increase GnRH
- increase FSH, LH
21 day cycle
tell me what the hormones are doing during fall transision
- increase melatonin
- decrease GnRH
- decrease FSH, LH
persistent follicles
tell me what the hormones are doing during anestrus (winter)
- increase melatonin
- decrease GnRH
- decrease FSH, LH
flaccid uterus, small ovaries
tell me what parameters you can use to predict ovulation in the mare
- follicular diameter
- uterine edema
- change in follicular shape
- thickening of follicular wall
- softening of the follicle followed by involution
tell me how to use follicular diameter to predict ovulation in the mare
35-60mm
basically 35mm or greater = ovulation
tell me how to use uterine edema to predict ovulation in the mare
edema maximized 24-36 hours prior to ovulation, decreases just before ovulation
tell me how to use change in follicular shape to predict ovulation in the mare
pointed on 1 side - becomes irregular
tell me how to use thickening of follicular wall to predict ovulation in the mare
follicular wall thickens - starting to leutenize
during ovulation, the follicular tone ___ and the follicular size ____
tone: softens
size: >35 mm followed by involution
why do we control the mare’s estrous cycle?
- to get them pregnant
- cycle becomes more predictable if we manipulate
- to work around show times
- so the vet can have a normal work schedule lmao
what parts of the estrus cycle are amenable to manipulation?
- prostaglandin
- ovulation
- progesterone
- melatonin
how do you induce ovulation in the mare?
hCG, deslorelin, or GnRH analogs
how do you use hCG to induce ovulation in the mare?
when does ovulation happen after admin?
follicle has to be ≥35mm (because it has action on LH and the follicle needs to be big enough for the LH follicles)
ovulation happens 36 hours after admin
why do we use GnRH analogs instead of native GnRH?
analogs have higher half life and can be a single shot only
how do deslorelin/GnRH analogs induce ovulation?
when does ovulation happen after admin?
induces release of endogenous LH
ovulation within ~40 hours
what is short cycling?
interrupting diestrus
how do you interrupt diestrus in the mare?
PGF2 alpha
a “hot shot”
after you give PGF 2 alpha to short cycle, what happens?
CL will response 5 days after ovulation
You give hot shot 5 days into diestrus, mares enter estrus in 3 to 4 days, and ovulation occurs within 7 to 10 days.
when is PGF2 alpha as a hot shot contraindicated?
when there is pregnancy. always check before giving hot shot!
How do you prolong diestrus?
exogenous progesterone analogs, like altrenogest (Regumate)
What are exogenous progesterone analogs used for?
prolonging diestrus:
- used to manage the transition period
- used to predict estrus during show season
- used to suppress all estrus activity
CAUTION WHEN USING REGUMATE/ALTRENOGEST! why ?
you can absorb through skin and chronic use affects human cycling - women have to be careful!
mares start cycling when in the spring?
late march/early April
spring equinox!
which can we manipulate, spring or fall transition? or both?
spring
why is there follicular development without ovulation during the spring transition?
LH lags behind FSH
during the fall transition, which declines first, LH or FSH? what does this mean?
LH
means follicular growth without ovulation
what is an autumn follicle?
follicle with large diameter that persistent with no concurrent uterine edema or signs of estrus
how do you manipulate seasonality?
manipulate the photoperiod - mimic spring (need 16 hrs light and 8 hours dark) - add light at end of day, not beginning
how long does it take to show effects when you manipulate photoperiod to change seasonality of mares?
6-8 weeks - then transition starts
we don’t skip transition!
what is the classic program for manipulating seasonality?
begin artificial light Dec 1
mare must be in ______ ____ when the mare and stallion are introduced to one another with natural service/live cover
standing heat
warmbloods tend to develop ____ follicles.
larger
fresh, cooled semen is viable for ____
48 hours
oocytes are viable for ____ after ovulation
12 hours
ideally, you breed ____ ____ ovulation
12 hours before
sperm need about _____ to travel to the oviduct
6 hours
for a 35mm follicle, you should use ___ to induce ovulation. for a 35-40mm follicle, you should use ___ to induce ovulation.
hCG
deslorelin
tell me the timeline for using fresh cooled semen for AI
- fresh cooled semen viable for 48 hours
- shipment takes 24 hour
- 35 mm follicle: hCG (takes 36 hours to induce ovulation)
- 35-40mm follicle: deslorelin (takes 40 hours to induce ovulation)
- inseminate 24 hours after administration of drug
- ovulation 12 hours later
- do post breeding US 24 hours later to confirm ovulation
true or false: it is negligent to allow a mare to carry twins to term
true
when is the earliest you can see an embryo on US?
12-14 days
when is the ideal time to check for pregnancy on US? why?
16 days
egg is mobile at this time. if twins, you can separate eggs to horns and pinch one off
what questions does the breeding soundness exam aim to answer?
what is the likelihood that this mare can:
- get pregnant
- maintain pregnancy
- what is the reason for infertility
- what is the reason for early embryonic death
should be discussed at EVERY pre-purchase exam on a mare, even if breeding isn’t the immediate goal for the horse
look at conformation!
what are the components of the breeding soundness exam?
- history
- PE (general)
- repro PE –> ideally during breeding szn (includes external genetalia, palpation of internal repro organs, endometrial cytology/culture)
- vulvar conformation
- palpation and US
- vaginoscopy
- uterine culture/cytology
why do we look at vulvar conformation during the BSE? how do we fix poor conformation?
vulva provides the first effective barrier to protect the uterus from ascending infection
Caslick’s vulvoplasty
the vaginoscopy during a BSE should be performed ____ (before/during/after) the palpation and US
after!
what is the easiest and most common diagnostic performed in the field for repro exam? when is it performed usually in the mare’s cycle?
uterine culture and cytology
during estrus
is the endometrial biopsy part of the normal BSE? what is it used for?
nope
used to investigate infertility when there’s early embryonic death or an inability to get pregnant
where is an endometrial biopsy taken and when during the cycle?
taken during estrus (more accurately predicts fertility)
at the base of 1 horn
infectious endometritis is more common in mares who _____
have poor vag conformation
what are the clinical signs of infectious endometritis?
vaginal discharge, intrauterine fluid, infertility, early embryonic loss
what pathogens are usually involved in infectious endometritis?
- strep equi subsp. zooepidemicus (uterine specific strains)
- E. coli (not uterine specific)
- Klebsiella pneumoniae
- Pseudomonas aeruginosa
- yeasts and fungi
how do you diagnose infectious endometritis?
- endometrial cytology
- culture and sensitivity
based on endometrial cytology, when do you know it’s infectious endometritis?
when endometrial cells:neutrophil ratio is <40:1
what is breeding induced endometritis?
physiological reaction to clear the uterine lumen - achieved through uterine contractions and the anti-inflammatory reaction
what happens to normal mares who have breeding induced endometritis?
endometrial inflammation cleared within 24-36 hours
what role do seminal plasma proteins play in breeding induced endometritis?
directing PMNs to dead spermatozoa
what happens to “susceptible mares” who have breeding induced endometritis?
- pathologic!
- delayed clearance of breeding-induced inflammation with possible impaired uterine contractility
- happens with frozen semen (low % of seminal plasma)
how do you dx breeding-induced endometritis?
uterine fluid 24-36 hours post AI
how do you treat breeding-induced endometritis?
- uterine lavage (Ringer’s) –> “dilution is the solution to pollution”
- oxytocin (wait 6h post AI)
- PGF2 alpha - might impair CL development - be careful
in the mare, does pyometra depend on the presence of a CL?
nope
true or false: in mare pyometra, accumulated pus is sterile
true
mare pyometra is often associated with ____. what is the most common cause?
cervical adhesions
poor cervical function is the most common cause
how do you treat mare pyometra?
uterine drainage/lavage (repeated), surgery to address cervical issues
what are these?
hemorrhagic follicles
they can be very painful!
are mare anovulatory follicles cysts like in cattle?
nope
what happens with anovulatory follicles in the mare?
initially, follicular development proceeds normally. then follicles “keep growing” and persists, and they persist for varying periods of time
what is the most common ovarian tumor in the mare?
granulosa cell tumor
granulosa cell tumors are ____ (malignancy) and ____ (uni/bi lateral) in the mare.
benign and unilateral
true or false. granulosa cell tumors can develop during pregnancy in the mare
true
what happens to the mare who has a granulosa cell tumor?
- stallion-like behaviour
- persistent estrus
- inhibin increases - contralateral ovary small
- increase testosterone
how do you diagnose granulosa cell tumors in the mare?
- US
-GCT panel (testosterone, inhibin, and progesterone) - AMH
what is the tx for a granulosa cell tumor in the mare?
sx
contralateral ovary resumes follicular activity on avg within 6 months
you do US and see a suspected granulosa cell tumour. what are your ddx?
hematoma, cystadenoma, teratoma, dysgerminoma
what are the clinical signs of an abnormal cervix?
infertility/subfertility
what are 2 types of cervical abnormalities in the mare?
- cervical adhesions
- insufficient cervical closure
cervical adhesions stem from ____ –> if severe, then ___ possible.
cervical lacerations (parturition)
pyometra possible
infectious endometritis is often ____ (chronicity) and the result of unresolved ____.
chronic, PBIE
what is pyometra?
large amount of pus and inflammatory debris in the uterus
end stage result of PBIE –> infectious endometritis –> pyometra
how do you dx pyometra?
- C/S are almost always absent!
- US, culture
ovulation failure typically results in a ___
lose of the cycle, may prevent return to heat, esp if partially luteinized
