Equine reproduction Flashcards
what is a mare?
female horse over 4 years old
what type of breeder is the mare?
long day, seasonal, polyoestrus
how long is the oestrus cycle of the mare?
21 days
how long is diestrus in the mare?
16-17 days
how long does oestrus last in the mare?
4-6 days
what does the dominant follicle do once recruited?
produce oestrogen
what does oestrogen produced by the dominant follicle do?
induce oestrus
what size does the dominant follicle have to be for ovulation to occur?
> 35mm
how long does oestrus continue after ovulation?
24 hours
what does the ovulation site become after ovulation?
(corpus haemorrhagicum) then corpus luteum
what does the corpus luteum produce?
progesterone
what causes luteolysis?
prostaglandin
what is the transitional period in relation to the mare?
period of change from anoestrus to normal cycling
what will be seen on the ovaries if a mare is scanned in the transitional period?
bunch of grapes (follicles that eventually regress)
are mares fertile in the transitional period?
no
what three hormones can be used to manipulate oestrus?
prostaglandins progesterons oestrogens chorionic gonadotrophin deslorelin
how can prostaglandins be used to manipulate the oestrus cycle?
induce luteolysis of a CL commencing oestrus 3-5 days later
how can progestogens be used to manipulate the oestrus cycle?
suppresses oestrus then removal leads to rebound ovarian activity (shorten oestrus)
what are oestrogens used for?
induce signs behavioural signs of oestrus (teaser mares)
what is chorionic gonadotrophin used for?
induce dominant follicle to ovulate
what is deslorelin used for?
induce ovulation in 48 hours with a follicle >30mm
how can light be used to manipulate oestrus?
16 hours of light and 8 hours of dark from 2-4 weeks before winter solstice
what can be used to suppress oestrus?
longterm progestogens intra-uterine device (not encouraged) anti GnRH vaccine long term CL (oxytocin injection) plant oil in uterus put in foal ovariectomy
when should mares be served in relation to ovulation?
24-48 hours before
what are the 4 signs a mare is in oestrus?
dominant follicle on one ovary
uterine oedema
soft oedematous cervix
behavioural signs
if a mare is in oestrus when scanned, when should you next scan her?
24-48 hours later
if a mare isn’t in oestrus when scanned, what should be done?
prostaglandin and scan in 3-5 days
how does the dominant follicle appear just before ovulation?
softer and pointing
how does oedema of the uterus appear appear 24 hours prior to ovulation?
starts to decrease
how long after mating should a mare be scanned?
12-24 hours
what should be looked for on a post mating scan?
has ovulation occurred (only one)
check for fluid in uterine lumen (endometritis)
what three mechanisms of perineal conformation are important for prevention of bacterial entry?
vulval seal
vestibular seal
cervical competence
what can failure of the vulval and vestibular seal lead to?
pneumovagina leading to urovagina causing cervicitis and endometritis
what is the most common procedure used in mares with poor perineal conformation?
casslicks vulvoplasty
what is casslicks vulvoplasty?
suture the vulva lips together (as much as necessary)
what effect does a persistent CL have?
no oestrus
what are anovulatory follicles?
very large follicles that don’t ovulate causing prolonged oestrus (prolonged luteal phase if they ovulate)
what are the three types of endometritis?
chronic infectious metritis
free fluid in lumen
mating induced endometritis
how long does the fertilised conceptus stay in the oviducts for?
5 days
what can be done to treat mating induced endometritis?
(should be self limiting) uterine lavage oxytocin intrauterine antibiotics AI
what is the gestation period of a mare?
336 days
where does fertilisation occur?
ampulla of oviduct
what does the embryo do when it enters the uterus?
migrates around for 15 days
what is the migration of the embryo around the uterus essential for?
maternal recognition of pregnancy (prevention of prostaglandin release)
when does placental attachment begin?
36 days
what produces progesterone to maintain the pregnancy?
CL
what maintains the primary CL during pregnancy?
eCG from endometrial cups
how long do CLs maintain the pregnancy for?
first 5 months
what maintains the pregnancy after CLs have degenerated?
progesterone from foetal placenta
how early does a mare need to be aborted if breeding wants to be done again in the same season?
before day 35 (before endometrial cups form)
how long after mating can a mare be put back to the stallion to see if oestrus behaviour has returned?
14-21 days (some still show signs if pregnant)
what substances in blood can be used to confirm pregnancy?
eCG (45-90 days) oestrone sulphate (120+ days)
what produces oestrone sulphate?
foetus (confirm viability and pregnancy)
what size is the foetus for manual palpation on day 20?
marble
what size is the foetus for manual palpation on day 40?
grapefruit
when should a first pregnancy diagnosis scan be done?
15-16 days (check twins)
when should a second pregnancy diagnosis scan be done?
24-26 days (heartbeat visible) - check twins and can terminate
when should a third pregnancy diagnosis scan be done?
6 weeks
when is the best time to do a pregnancy diagnosis scan if only one is being done?
28-35 days
how far into gestation can transabdominal ultrasound be used for pregnancy diagnosis?
6 months
what is early embryonic death?
death from fertilisation to day 40
