Reproductive problems in the mare Flashcards
(62 cards)
1
Q
lA maiden mare is presented to stud - what is the plan with her?
A
- establish mare is normal
- establish stage of cycle and attempt to get into oestrus asap
2
Q
A pregnant mare is presented to stud - what is the plan with her?
A
- aim to breed at foal heat
3
Q
A barren mare is presented to stud - what is the plan with her?
A
- understand previous breeding management
- establish diagnosis and likely prognosis
- treat any undetected endometritis
- establish stage of cycle and attempt to get into oestrus asap
4
Q
Signs of foal heat
A
- 5-10d post partum
- foal develops d+
- oestrus may be silent
- no endometrial sloughing after parturition
5
Q
Should you cover at foal heat?
A
- easy to identify and useful in mares that foal late
- but, lower conception rate and increased pregnancy loss
- do if: post-partum events normal, mare foaled late in year
- don’t if: poor involution or fluid present
6
Q
Prolonged dioestrus - cause
A
- caused by persistence of secondary CL in absence of pregnancy
- occurs as a result of a dioestrus ovulation
- ovulation occurs in the luteal phase (the mare doesn’t show oestrus behaviour)
- the mare produces PG at the normal time which lyses the primary CL but not the new CL (as 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)
7
Q
Prolonged dioestrus - prevalence
A
- up to 24$ of cycles (ie is common)
8
Q
Prolonged dioestrus - signs
A
- failure to return to oestrus
- uterus and cervix are typical of luteal phase
- ovaries may be large as follicle growth continues, this may confuse the inexperienced
9
Q
Prolonged dioestrus - tx
A
- single dose of PG to lyse the persistent secondary CL
10
Q
Erratic oestrus during transitional phase - tx
A
Providing 16h of artificial light and additional nutrition from 1st December
- some clinicians also administer GnRH agonists at this time but efficacy is unproven
Once the mare is within the transitional period (follicles >2.5cm diameter) progestogens are administered to suppress the release of LH
- normally altrenogest (Regumate) is given in feed for approx 10d
- follicles continue to grow during progestogen tx
- when follicles reach 4.5cm progestogen tx stops and there is a surge release of LH which induces ovulation
— some clinicians also administer GnRH at this time to enhance the LH release
- ovulation normally occurs 8-12d after the last dose
11
Q
How to get them into oestrus and breed asap?
A
- shortening luteal phase
- hastening ovulation
12
Q
Shortening the luteal phase
A
- most common method of manipulating the cycle is administration of prostaglandin
- causes lysis of CL and a return to oestrus: the speed of response depends on stage of follicle growth at the time you administer the PG
- single dose PG between d5-12 causes return to oestrus in 4-6d (but ovulation may take up to 10d early in the breeding season)
13
Q
Hastening ovulation
A
GnRH agonists (ovuplant) or hCG (chorulon)
- place GnRH implant of inject hCG when follicle 3.5cm in diameter
- ovulation should occur within next 48h
- therefore plan breeding 24h after injection
14
Q
When is the optimum time for mating in a normal mare?
A
- 24-48h before ovulation
15
Q
Abnormalities of cyclicity (in some order to how common)
A
- prolonged dioestrus
- erratic oestrus during transitional phase
- absent oestrus post-partum
- silent oestrus
Uncommon conditions
- nymphomania
- granulosa cell tumour
- failure to reach puberty
16
Q
Do cystic ovaries occur in horses?
A
- no
17
Q
Causes of absent oestrus post-partum
A
- the mare that fails to show the foal heat and fails to show subsequent cyclicality
- seasonal anoestrus: mares that foal early in the year (and therefore should not be expected to return to cyclical activity)
- foal shay: mares that are protective of the foal and although they have follicle development and ovulation they suppress behavioural signs - the mares that do show foal heat and then fail to show cyclicly after that
- prolonged dioestrus: mares that ovulate and then have a persistent CL usually associated with dioestrus ovulation
18
Q
Tx of seasonal anoestrus
A
- no tx except increasing nutrition and lighting and attempting to bring the mare into the transitional phase and then using progestogens
19
Q
Tx of foal shy
A
- the mare may show oestrus if the foal is placed in front of the mare away from the stallion
- mare may need to be distracted or restrained
- AI may be performed if necessary (or allowed)
20
Q
Silent oestrus - what is it?
A
- the mare that will not show signs of oestrus or will not allow mating although other examination confirms she is in oestrus and close to ovulation
- care to not mistake dioestrus follicles with a mare that is in oestrus
21
Q
Dioestrus follicles vs mare in silent oestrus
A
With dioestrus, the mare has a follicle and CL. The CL is dominant but can’t be palpated and so can be mistaken for oestrus.
The easiest way to tell if to palpate the cervix - will be closed in dioestrus and open in oestrus.
22
Q
Silent oestrus - which mares is it usually seen in?
A
- maiden mares or mares with a foal at foot
23
Q
Silent oestrus - tx
A
- if the mare can see that the foal is safe she will often show oestrus
— foal held into front of mare often in a pen - mare may need to be distracted or restrained
- AI may need to be performed if necessary (& allowed)
24
Q
Does true nymphomania occur in mares?
A
- no
25
What different types of behaviour can O think is 'nymphomania', what these actually are & potential tx/management options
Persistent oestrus during the transitional period
- here oestrus behaviour is normal but prolonged
Mares that are difficult to handle during oestrus
- here mares have normal cycles but are difficult when in oestrus
- ovariectomy may help in their management
-- success can be predicted by a good response to progestogen administration
'Bad mares'
- here mares are vicious and may squirt urine when showing aggression
- they are hormonally normal and do not respond to ovariectomy
- i.e. not associated with cycle/reproductive activity, just mean
- sometimes progestogen tx produces some improvement because of its central sedative / behaviour modification effects
Granulosa cell tumour
- here CS are persistent low level or normal oestrus (or virilisation or anoestrus but not nymphomania)
26
`Granulosa cell tumour - signalment
- most commonly recognised in young mares
27
Granulosa cell tumour - US appearance
- mixed solid and multi-cystic appearance
28
Granulosa cell tumour - what does the other (non-affected) ovary look like? Why?
- small
- down regulated HPG
- if the other gonad is producing high concentrations of any hormone, the negative feedback look drives the hypothalamus/pituitary less, therefore the other ovary is no longer stimulated and will atrophy
29
Granulosa cell tumour - tx
- unilateral ovariectomy
- hopefully the HPG will reactivate and the other ovary will start to cycle
- often cyclical activity in the contra-lateral ovary doesn't recover until the next season
30
Granulosa cell tumour - reproductive CS (depending on what hormone is produced)
- if produce oestrogen = persistent oestrus
- if produce progesterone = persistent anoestrus
- if produce androgens = virilisation (muscular changes and stallion-like behaviour)
- plasma inhibin concentrations may be elevated
- they don't produce nymphomania, rather persistent oestrus
31
Procedure for ovariectomy in mares
- either in standing mare with flank incision or recumbent mare with para-median incision
- helpful to palpate per rectum to see where the ovary can be moved to as this facilitates planning of incision
- routine approach, exteriorise ovary and ligate pedicle or use stable
- some surgeons still use an Ecraseur
- often difficult to remove, difficult to get the pedicle as they're often so big
32
Failure to reach puberty in the normal mare - cause, what does their reproductive tract look like?
- mares that are in racing yards may fail to reach puberty when expected esp if the training regime is severe
- this is normally not a problem until the mare has an injury and it is unexpectedly suggested that she is bred from
- these mares have small inactive reproductive tracts typical of anoestrus
33
Failure to reach puberty in the abnormal mare - cause, how do they present?
Mares with chromosomal abnormalities such as Turners syndrome (63XO) are rare but present with
- small reproductive tract (e.g. ovaries less than 1cm)
- abnormal/small external genitalia
- requires blood sample for karyotype
34
Reasons why mares are thought to have ovarian cysts
- mares ovaries and follicles are larger cf cows and may be mistaken as abnormal
- during spring transitional phase ovaries are normally large and contain many non-ovulating follicles
- during prolonged dioestrus ovaries are normally large and contain may non-ovulating follicles
- during early pregnancy the secretion of eCG results in significant follicle growth and luteinisation ovaries can be huge
35
Cysts close to the ovaries that can be found at PM
- fossal cysts
- bursal cysts
- adrenocortical cysts
36
Other common reproductive anomalies
- endometritis
- luteinised/haemorrhagic (anovulatory) follicles
37
Causes of endometritis
- poor perineal conformation (wind-sucking)
- mating-induced endometritis (susceptible mares)
- chronic endometritis (from a previous episode that doesn't resolve)
- long standing chronic endometritis with endometrial fibrosis
38
Factors contributing to endometritis
- poor body condition (anus sinks cranially and vulval conformation changes)
- urovagina
- cervicitis
- cervical trauma
- uterine sacculation
- uterine adhesions
- uterine FB
39
When are luteinised haemorrhagic follicles seen usually?
- tend to be seen towards the end of the breeding season
- perhaps more common in the older mares?
40
Luteinised haemorrhagic follicle - what is it / cause?
- follicles that reach ovulatory size but do not rupture
- the oocyte is not released and therefore conception can't occur
- follicles continue to increase in size and the 'CH' becomes larger than expected
- progesterone increases and the mare goes out of oestrus
- the breeder may assume as is well but conception cannot occur
41
Luteinised haemorrhagic follicle - what does it look like?
- criss-crossing strands of fibrin within the enlarged follicle cavity
42
Luteinised haemorrhagic follicle - US changes & tx
- initially haemorrhage occurs (echogenic spots)
- the follicle doesn't 'point' towards the ovulation fossa and follicle collapse doesn't occur
- progressive luteinisation results in the structure gradually increasing in echogenicity
- the resultant luteal structure is responsive to endogenous PG and therefore the cycle interval is usually normal (unless the mare enters anoestrus)
- tx (if necessary) is exogenous prostaglandin administration
43
Luteinised haemorrhagic follicles vs ovarian tumour
- sometimes these follicles continue to have bleeding which can be very significant
- this results in 1 very large ovary
- this can be differentiated from an ovarian tumour since there would be no decrease in size of the contralateral ovary
44
Mare with large ovaries - ddx
- transitional phase
- pregnancy
- prolonged dioestrus
- pseudopregnancy type 2
- luteinised/haemorrhagic follicle
- GCT
45
Vulval disease - examples
- coital exanthema
- vulval tumours
46
Endometrial disease example of incidental finding
- endometrial cysts
46
Vaginal disease - example of incidental finding
- varicose vessels
47
Ovarian disease example of incidental finding
- para-bursal cysts
48
Coital exanthema - cause
- equine herpes virus 3
49
Coital exanthema - disease process
- relatively benign for the mare
- mare reamins carrier for life with viral recrudescence when stressed
- initial acute infection established by transmission from stallion after coitus resulting in vesicles 5-7d later
- vesicles rupture leaving ulcers which then heal
- in vesicle and early ulcer stage the mare is infectious and virus can be transmitted by equipment, etc
- pregnancy rates not affected
- don't cause resorption or abortion, just a local problem (i.e. lesions)
- if stallion is infected then lesions on penis can be so painful as to prevent coitus
50
Coital exanthema - tx
- symptomatic tx only required
51
Vulval tumours - most common example
- melanoma is common esp in older grey mares
52
Vulval tumours - do they affect breeding/fertility?
- often the lesions are small and not significant for breeding or fertility
- friable so can split if vulva is dilated
- sometimes breeding causes abrasion to the nodular tumours but this can be treated conservatively
53
Vaginal varicose vessels - where do they originate?
- may originate form the lateral vaginal wall in older mares
54
Vaginal varicose vessels - cause
- presumably arise as a result of previous abrasion/trauma at foaling
55
Vaginal varicose vessels - problems
- appear to be largest when the mare is in oestrus or during pregnancy, when they may protrude from the vulval lips
- sometimes when the lesions are large they're traumatised at mating or parturition and then bleed
56
Vaginal varicose vessels - tx
- if bleed ligation may be necessary
- in some cases this may requires an episiotomy approach
57
Endometrial cysts - what are they associated with?
- may be associated with endometrial dz
58
Endometrial cysts - prevalence
- seen more commonly in older mares
- very common in mares with normal fertility
- analysis of large numbers doesn't support a primary role in infertility, therefore they do not
59
Endometrial cysts - tx
- analysis of large numbers doesn't support a primary role in infertility, therefore they do not need to be treated in the majority of cases
- very occasionally large cysts may block conceptus migration and result in failure of maternal recognition of pregnancy
-- these cysts might be removed using endoscopic puncture
60
Endometrial cysts - what can they be confused with? why?
- conceptus as fluid filled
61
Endometrial cyst vs conceptus
- cysts often irregular in outline
- cysts frequently lobulated
- cysts don't always have a dorsal and vernal specular echo
- cysts don't change in position
- cysts don't increase in size
- large cysts don't contain an embryo whilst this can be consistently seen in the conceptus after d21
