Horse Reproduction Flashcards
what is a gelding?
castrated male
what is a filly?
female <2yo
what is a colt?
entire male <4yo
what is the stud?
stallion or breeding establishment
what does ‘to cover’ mean?
to mate
what is a teaser?
male used to test mare in season
what is an embryo?
conceptus <50 day old
what is a foetus?
conceptus >50 day old
what is a cryptorchid/rig?
male behaving as entire male with non-scrotal testicles
what type of oestrus cycle do mares have?
seasonally polyoestrus
what time of year do mares naturally cycle?
spring-autumn
brought on by increasing day length and ceases as days shorten
how long is the oestrus cycle in mares?
21 days
what is the most desirable time of year to foal?
late spring-early summer
easier to maintain mare and foal at grass
when should mares be covered?
during the month after you wish them to foal in (pregnancy lasts around 11 months)
how does covering time differ between pleasure/performance breeds and thoroughbreds?
covering starts earlier with thoroughbreds
why is it advantageous for thoroughbred foals to be born as early as possible in the year?
when racing, there is an appreciable benefit to being as mature as possible within your year group - a group of horses race with their calendar year peers
when are thoroughbred mares covered?
from valentines day onwards
where do mares foal?
some will foal at the stud where they will be covered
others will foal at home before travelling mare and foal to stud (‘foal at foot’)
how is ovulation induced?
use of prostaglandin which causes corpus luteum regression
mare will cycle within 2-7 days of injection
what pre-breeding checks should be performed before/upon arrival at stud?
general health - strangles, clinical examination
clitoral fossa and sinus ENT swabs (in amies charcoal)
why are clittoral fossa and sinus swabs taken during pre-breeding checks?
to check for diseases which cause contagious equine metritis
what is contagious equine metritis?
highly transmissible venereal disease causing uterine inflammation
what pre-breeding checks should be carried out on the mare at stud?
endometrial swabs (cytology, C+S)
ultrasound scan of ovaries for follicle development
and uterus to check free fluid and cysts
what is teasing?
testing whether or not a mare is in season using a male horse
what type of horse is usually the ‘teaser’?
low value, often pony stallion - cheap, less consequence if injured during teasing, may cover nanny mares to keep him interested
may be the stud stallion in some cases
how is teasing carried out?
may introduce head to head or teaser to mares rear
can use teasing boards/stable door/fencing/open area
what is oestrus behaviour in the mare?
lifting tail
winking of vulva
squirts urine
wide-legged stance
acceptance of male presence
does not kick out at stallion
tolerates his attention
what is oestrus behaviour in the stallion?
flehmen response sniffs/nuzzles them bites hindlimbs and perineum drops penis penile erection if permitted will cover the mare
why might a mare be US scanned during oestrus?
to determine the best time to cover
what are you looking for during US of a mare in oestrus?
large follicle (5cm diameter)
uterine oedema
no free fluid in uterus
what does the cervix look like during oestrus?
red, engorged, saggy
closer to ventral floor of vagina
what does the cervix look like during dioestrus?
pale, small, tight
high up off vaginal floor
what type of covering does weatherbys allow?
to be weatherbys registered, mares must be covered naturally - no AI
covering certificate issued to mare owner by the stud
how is in-hand covering carried out?
stallion walked to mare from behind and allowed to greet
stallion mounts then covers mare
stallion handler may palpate ventral penis for ejaculation
what are the safety considerations for in-hand covering?
humans - hats, safety footwear, gloves
mare - wither guard, hobbles, bridle, twitch, boots, tail bandage
stallion - bridle/chain, lunge line, foot boots
how soon after covering should you tease/US?
following day -
if still in oestrus may cover again (every other day)
if not in oestrus manage as normal - tease from 18 days and US from 12 days
when does unassisted covering occur?
in herd or individual short term or living in herd free in field common with native breeds timings determined by horses - less human intervention
what types of semen can be used in AI?
fresh semen from local stallion
chilled semen from stallion in same country
frozen semen - global possible
how is semen collected with a dummy?
train stallion to dummy (artificial vagina)
soak towel in urine from mare in season to encourage
OR stand in-season mare nearby/in front
how is semen collected using a mare? why is this not commonly performed?
use of a sedated/ovarioectomised/in season
questionable welfare for mare if needs restraint repeatedly
what is the setup of an artificial vagina?
lined, lubricated and insulated filled with warm water (38°C approx) semen collection vessel insulated filter gel from semen do not get water in semen!
what is semen extender?
preserves fertilising ability of the sperm in semen
how is timing of AI decided?
usually upon US scan - when uterine oedema subsided, minimal free fluid
fixed time insemination can be used following induction of ovulation
how much sperm is used for AI?
typically 100-500 million progressively motile sperm
how us AI performed?
use of speculum to visualise or hand per vaginum to guide
place insemination catheter through cervix into uterus
instill semen dose into uterine body
what is involved in post-covering/AI management?
removal of free fluid associated with semen/extender/inflammatory reaction (lavage, induce uterine contractions, encourage movement)
vulvoplasty caslicks procedure to prevent ascending infection into uterus
monitor with US to check free fluid levels
how old is the embryo used for embryo transfer?
7-10 day blastocyst - collected from donor mare and transferred to recipient mare
how can pregnancy be diangosed?
US scan from 12 days
failure to return to oestrus by 21 days
blood sample (PMSG or oestrone sulphate)
urine sample from 120 days (placental oestrogens)
when can a eCG blood test be performed to confirm pregnancy?
from 60 days
when can an oestrone sulphate blood test be performed to confirm pregnancy?
from 120 days (indicates whether foetus alive or not)
what is the conception rate in horses?
approx 80%
are live twins common in horses?
no - rarely survive to full term
when are twins typically aborted?
between 5-7 months when demands exceed placental surface area capacity to provide required nutrients and oxygen
how can twins be aborted if found on US?
can terminate one or both
“pinching” - easiest before implantation at day 14-18
must terminate before endometrial cups sustain pregnancy (d35)
what is the gestation range?
320-370 days (approx 340 usually)
when is the foal considered premature?
if born 310-325 days
when is a fetus non-viable?
before 310 days - will abort
what are the signs of imminent foaling?
udder development - waxing up, dripping milk
vulva relaxes
foaling alarms - use sweating
how do electrolytes in the milk change if foaling imminent?
calcium increase and sodium decreases
are caesarians performed in horses?
possible under GA
not usually done in the field unless mare will not survive regardless
how long does stage 1 labour last?
1-4 hours
what happens during stage 1 labour?
foal enters pelvic canal, stimulating dilation of cervix and vulva
uterine contractions of increasing strength from tip of horns to cervix
what are the behavioural signs a mare is in stage 1 labour?
restlessness getting up and down looking at abdomen sweating frequent urination
what should be done when it is noticed the mare is in stage 1 labour?
wash perineum
bandage tail
reverse caslicks with an episiotomy
how long does stage 2 labour last?
15 mins
what happens during stage 2 labour?
allantois ruptures at cervical star releasing fluids
strong contraction from uterus and voluntary abdominal contractions
amnion then visible with foal inside
what happens to the foal during stage 2 labour?
foal presents 2 toes and nose
shoulders and body of foal expelled
hindlimbs retained in uterus and mare rests
when mare stands, umbilicus breaks
what happens in stage 3 labour?
uterine contractions from tip of horns to cervix
inverts placenta and expels it and lochia (fluids)
how long does stage 3 labour last?
should be <3 hours
what if the afterbirth does not come within 3 hours of birth?
if retained >3 hours seek urgent veterinary advice as retained foetal membranes may cause endotoxaemia
what are the 6 layers of the epitheliochorial placenta?
- chorionic capillary endothelium
- chorionic connective tissue
- chorionic epithelium
- endometrial epithelium
- uterine connective tissue
- uterine capillary endothelium
what type of placenta do horses have?
non-deciduate - foetal and maternal layers separate
diffuse - villi spread over virtually all the placenta
how can it be ensured that the placenta has been passed in entirety?
collect from stable before traumatised
examine both surfaces
distend with fluid (only possible if no tears) - shows complete removal
which part of the placenta is most likely to be retained?
tip of non-pregnant horn
what are the signs the mare is experiencing dystocia?
(once allantochorion ruptures)
no amnion or foal at vulva within 5 mins
no strong contractions within 10 mins
no progression of foal made over a 5 min period
what are the options if there is dystocia?
vaginal assisted delivery
controlled vaginal delivery
C section
embryotomy
euthanasia (foal delivered under GA C section then mare euthanised)
what are the survival rates for elective C section?
90% for mare and foal
what are the survival rates for emergency c section?
directly relates to time of onset of stage 2 labour
what is the 1 2 3 rule?
stand in 1 hour
suckle by 2 hours
placenta passed within 3 hours
which horses need a passport?
all horses born since 2005
which horses need a microchip?
all horses (since 2018)
what is a passport required for?
travelling with horse
selling horse
slaughtering horse
when should a passport application be made?
application to be made by december 31st of year born or when foal is 6 months old (whichever is later)
what is included in the passport application form?
owner details
microchip status/location
ID certificate (not compulsory to complete but advisable)
owner and competent authority (vet) signature
vet stamp
where is a microchip placed?
nuchal ligament
how do you insert a microchip?
scan neck to ensure not present
scan chip to ensure correct number
insert into nuchal ligament
scan neck to ensure in situ
