Reproductive Problems and Pregnancy Loss in the Mare Flashcards
What categories can mares be in when they arrive at stud?
- maiden
- foal heat
- barren
What are the signs of foal heat?
- 5 – 10 days post partum
- Foal develops diarrhoea
- Oestrus may be silent
What are the pros and cons of breeding at foal heat?
Pros
- Easy to identify and useful in mares that foal late
- Do if: post-partum events normal, mare foaled late in year
Cons
- No endometrial sloughing after parturition
- Lower conception rate and increased pregnancy loss
- Don’t if: poor involution of fluid present
Molly Malone ovulated 10 days ago on her right ovary and has a non-palpalable CL.
She has a 35mm follicle on her left ovary.
* Which structure is ‘dominant’?
* Why does she have this follicle?
* Might it ovulate?
* What will happen if it ovulates in a few days time?
Dominant structure - 10 days after ovulation, CL is dominant
She has this follicle because of follicular wave but isn’t likely to ovulate because she has high progesterone
- waves of follicular development and regression if environment isn’t suitable
If progesterone decreases, she may ovulate in the luteal phase
What causes prolonged dioestrus? What clinical signs are associated? How can it be treated?
- Caused by persistence of secondary CL in absence of pregnancy
- Up to 24% of cycles (i.e. it is common)
- Occurs as a result of a dioestrus ovulation
- Ovulation occurs in the luteal phase (the mare does not show oestrous behaviour)
- The mare produces PG at the normal time which lyses the primary CL but not the new CL (because it is too young and doesn’t respond to PG)
- The new CL can persist for up to 3 months (there is no further release of PG to lyse it)
- Uterus and cervix are typical of luteal phase
- Ovaries may be large as follicle growth continues; this may confuse the inexperienced
- Clinical signs are a failure to return to oestrus
- Treatment is single dose of PG to lyse this persistent secondary CL
It is 28th February. Dimple is a 6 year old TB mare that has been under lights since 1st December. She was teased 10 days ago and showed good oestrous behaviour and so was covered. She has been bred every other day since then.
Ultrasound imaging of the ovary and uterus, and speculum examination of the cervix are shown
- Describe the features
- What is going on?
- What do you need to do?
- Left and right ovaries - has medium sized follicles on both - moreso than she should at this time of year
- Ovaries will be size of fist
- Uterus has oedema within it
Transitional phase - high oestrogen concentration
Still in oestrus - follicle hasn’t reached ovulatory size
Treatment
- give oral progesterone (regumate for 10 days
- negative feedback effect - stop progesterone and will increase release GnRH
- Follicle will grow and ovulate which will kickstart breeding season
- exogenous GnRH or HCG to prompt follicle to ovulate
It is March 25th. Glossy Girl foaled in February and the foal heat was observed 7 days ago
Ultrasound imaging of the ovary and uterus, and speculum examination of the cervix are shown
- Describe the features in the images
- What is going on?
- What are you going to do?
On ovary image can see follicles and CL (dominant structure)
On uterus image - there is no oedema - not under influence of oestrogen
Under infleunce of progesterone from CL
Would give prostaglandin to lyse CL so one follicle will grow and ovulate
How can we shorten the luteal phase in the mare? Why would we want to?
- Most common method of manipulating the cycle is administration of prostaglandin
- Remember that this causes lysis of CL and a return to oestrus: the speed of response depends upon the stage of follicle growth at the time you administer the PG
- Single dose of PG between day 5 and 12 causes return to oestrus in 4 to 6 days(but ovulation may take up to 10 days early in the breeding season)
Jacinda is an 7 year old Irish Draft mare. She was inseminated with chilled semen shipped from Ireland yesterday.
Ultrasound imaging of the ovary (top) and uterus (bottom) are shown
- Describe the features
- What is going on?
- What are you going to do in this case?
- What actions do you need to take with respect to the ovary and why?
- What actions do you need to take with respect to the uterus and why?
On image of ovary - there is a follicle that is no longer round which indicates ovulation fossa (close to ovulation but hasn’t ovulation)
On image of uterus - fluid in uterus and oedema pattern in the wall
Mare is still in oestrus - but shouldn’t have fluid in her uterus 24 hours following breeding (should disappear after 4-6 hours following breeding)
Sign of breeding induced endometritis
Take sample from uterine fluid - expect to see >5 neutrophils per medium power field
Treat endometritis
How can you prompt ovulation in the mare?
GnRH Agonists (Ovuplant) or hCG (Chorulon)
* Place GnRH implant or inject hCG when follicle 3.5 cm in diameter
* Ovulation should occur within next 48 hours
* Therefore plan breeding 24 hours after injection
Hetty is 8 years old and presents in February for a BSE
Her vulva slopes slightly cranially but is not far from normal
Ultrasound of the uterus is shown
Describe the features you can see on the ultrasound image
What is going on?
What do you need to do?
On uterus image - bright echogenic structures in the lumen (sign of gas in uterus) because of slopey vulva
Indicates she is predisposed to developing endometritis
Surgical correction
What factors contribute to endometritis?
- Poor body condition (anus sinks cranially and vulval conformation changes)
- Urovagina
- Cervicitis
- Cervical trauma
- Uterine sacculation
- Uterine adhesions
- Uterine foreign body
What mares are most likely to have granulosa cell tumours? How do they present? What reproductive clinical signs are associated? How is it treated?
Most commonly recognised in young mares
Presentation depends on who you are!
* Medics see them as having colic
* Theriogenologists seen them as having abnormal cyclicity
* Practitioners see them as incidental findings
Reproductive clinical signs
* If produce oestrogen = persistent oestrus
* If produce progesterone = persistent anoestrus
* If produce androgens = virilisation
* Plasma inhibin concentrations may be elevated
* They don’t produce nymphomania rather persistent oestrus
Usually there is negative feedback so one ovary is very large whilst the other is very small
Treatment
- Unilateral ovariectomy
- Often cyclical activity in contra-lateral ovary does not recover until the next season
When does pseudopregnancy type 1 occur?
Pregnancy failure between day 15 and day 36
- mare has recognised that she is pregnant
- there is no return to oestrus
- primary CL will persist for its normal lifespan (about 40 days)
- CL can be lysed by the administration of prostaglandin
When does pseudopregnancy type 2 occur?
Pregnancy failure between day 36 and day 140
- endometrial cups will have formed
- there is no return to oestrus
- the secondary CLs will persist for their normal lifespan (about 150 days)
- secondary CLs cannot be lysed by the administration of prostaglandin and there is no mechanism to remove the endometrial cups
What occurs if pregnancy fails between day 1 and 5?
- pregnancy fails whilst in the oviduct
- mare has normal oestrus cycle as if never pregnant
What occurs if pregnancy fails between day 5 and day 15?
Mare has normal oestrus cycle as if never pregnant unless the pregnancy loss is associated with uterine inflammation - in which case there may be a short cycle
When does resorption, mummification and expulsion occur?
- Resorption if death of embryo
- Mummification if death of fetus whilst endometrial cups present (secreting eCG)
- Expulsion if fetal death after endometrial cups regress
When does abortion not occur following foetal loss?
when there are twins and one foal dies between day 80 – 150 whilst the other remains alive
How can chronic endometrial disease cause embryonic death?
- If the uterus is abnormal (eg has fibrosis, glandular abnormalities) it may be difficult to form a normal placenta and resorption may occur
- Sometimes called ‘Endometrosis’
- Detected on endometrial biopsy
What are infectious abortion causes? How are these investigated?
- Equine Herpes Virus
- Equine Viral Arteritis
- Placentitis (ascending commensals)
- Systemic infections
- Equine Infectious Anaemia
- Appropriate samples (fresh whole fetus, membranes and mare’s serum) should be sent to appropriate pathologist unless you are certain it is non-infectious
- If considered infectious plans must be implemented to isolate the infected mare and to prevent movement onto and off the stud
What are non-infectious causes of foetal abortion?
- Multiple conceptuses
- Umbilical cord abnormalities
- Uterine torsion
- [low progesterone]
- [stress]
- [severe malnutrition]
What is the prevalence of multiple ovulations?
- Incidence of multiple ovulations is 20%
- Prevalence of twins at 14 days is 10% of pregnancies (less in some breeds)
When do multiples conceptuses cause foetal abortion?
Incorrect diagnosis at 14 days caused by:
* Incomplete examination of the uterus (conceptuses are mobile)
* Failure to recognise twins
* Confusion of endometrial cysts
* Not counting the number of CLs
* Outcome is rarely successful as a result of competition for placental attachment area
