Non-infectious infertility and abortion in mares

Question 1

Hormonally based conditions causing infertility (4)

Answer 1

• Seasonal anoestrus
• Transitional anoestrus
• Prolonged dioestrus
• Haemorrhagic anovulatory follicles

Question 2

Anatomical causes of infertility (3)

Answer 2

• Persistent hymen
• Poor vulval conformation
• Cervical adhesions or tears

Question 3

Miscellaneous causes of infertility (4)

Answer 3

• Poor teasing
• Ovarian tumours
• Cysts
• Chromosome abnormalities

Question 4

Mid season problems (3)

Answer 4

• Non-cycling barren mares
• Non-cycling lactating mares
• Non-conceiving mares

Question 5

Late season problems (2)

Answer 5

• Non-cycling
• Non-conception in the season

Question 6

Issues in the pregnant mare (6)

Answer 6

• Twisted umbilical cord
• Undiagnosed twins
• Uterine body pregnancy
• Endometrosis
• Endometrial cysts
• Chromosome abnormalities

Question 7

Seasonal anoestrus

Answer 7

Neutral to teaser, ovaries small, cervix pale, blood progesterone low
Increase food supply, provide artificial lighting
Can give SQ low dose, slow release GnRH analogue or daily IM injections of GnRH analogues

Question 8

Transitional oestrus

Answer 8

Shallow oestrus: mare is neutral/positive to teaser, partially active ovaries, no dominant follicle, cervix variable, blood progesterone low
Spring oestrus: strong or erratic oestrus behaviour for some weeks
10 day course oral progesterone or IM progestagens with oestradiol 17B
Follow with IM injection of PGF2a
Scan ovaries 3-5 days later

Question 9

Prolonged dioestrus

Answer 9

Anti-teaser, partially active ovaries but unlikely to be a CL, cervix pale and tight, blood progesterone high
Inject PGF2a IM and re-examine in 3-5 days

Question 10

Haemorrhagic anovulatory follicles

Answer 10

Cause of ovulatory failure
HAF fails to rupture but increases in diameter
Treatment limited but can do interfollicular treatment with PGE2 and PGF2a

Question 11

Persistent hymen

Answer 11

Not common
Usually ruptured at time of first mating
Must rupture manually if not

Question 12

Poor vulval conformation

Answer 12

Very common
Causes pneumovagina leading to persistent endometritis
Vulva should be on vertical line with anus above
Bony level of pelvis should be at the top of the vaginal opening
Walls of vagina should be in apposition
If seals are not correct a caslicks is required

Question 13

Cervical adhesions or tears

Answer 13

Caused by difficult previous foalings
Not easy to repair
Poor breeding prognosis if cervical competence is compromised

Question 14

Poor teasing

Answer 14

One of the most common causes of sub-fertility

Question 15

Ovarian tumours

Answer 15

Granulosa (theca) cell tumour is relatively common
Most are slow growing and benign
Usually around 10yrs old (12-20)
Hormonally active and can secrete excessive amounts of testosterone, oestrogens, inhibin, and AMH
3 different behaviour patterns possible:
- Persistent anoestrus
- Stallion like behaviour
- Persistent oestrus
Usually only one ovary affected -large, palpable loss of ovulation fossa, multi-cystic ‘honeycomb’ looking structure on US
Haematomas or areas of necrosis are common
Serum anti-Mullerian hormone levels are 98% reliable
Remove affected ovary

Question 16

Cysts

Answer 16

Ovarian cysts are extremely rare
Ovulation fossa inclusion cysts may affect fertility due to ovulation impedance
Paraovarian cysts may be seen but are often incidental

Question 17

Chromosome abnormalities

Answer 17

XO condition (Turners syndrome) is most common
Tiny streak ovaries and an underdeveloped uterus
Use sterile heparinised blood sample to test

Question 18

Non-cycling barren/maiden mares

Answer 18

Poor teasing management or silent ovulations leading to prolonged dioestrus
Scan ovaries and/or measure blood progesterone for evidence of CL
Treat with PGF2a analogue

Question 19

Non-cycling lactating mares

Answer 19

Suspect prolonged dioestrus or genuine lactation related anoestrus, distinguish with blood progesterone levels
Prolonged dioestrus: PGF2a analogue
Lactational anoestrus: low dose SQ GnRH analogue implant

Question 20

Non-conceiving mares

Answer 20

Suspect prolonged infective endometritis
Take endometrial smear
Scan uterus for evidence of fluid accumulation
Endometrial cysts common in aged, multiparous mares suffering from endometrosis, may impede movement of blastocyst

Question 21

Late season- non-cycling

Answer 21

Suspect inadequate teasing during season or occurrence of spontaneous prolonged dioestrus

Question 22

Non-conception in the season

Answer 22

Suspect sub-fertile stallion, persistent acute infective endometritis or endometrosis, or multiple endometrial cysts

Question 22

Non-conception in the season

Answer 22

Suspect sub-fertile stallion, persistent acute infective endometritis or endometrosis, or multiple endometrial cysts

Question 23

Twisted umbilical cord

Answer 23

Commonest non-infectious cause of abortion
Usually due to an excessively long cord
Sometimes increased foetal activity

Question 24

Undiagnosed twins

Answer 24

High incidence of twin ovulation in TBs
Need early diagnosis with US
Manual rupture of one conceptus
If left untouched about 70% will abort mid/late gestation

Question 25

Uterine body pregnancy

Answer 25

Incorrect site of implantation
Lack of space/distension for normal development
Should implant at base of horn

Question 26

Endometrosis

Answer 26

Can lead to inadequate placental interdigitation and foetal starvation
If mares do not abort they tend to give birth to low-birthweight foals