Equine parturition

Question 1

Gestation length of a mare

Answer 1

Avg 340d (320-365)

Question 2

What factors may influence the length of gestation?

Answer 2

At what point of the season the mare falls pregnant
- early season = 10d longer than late in season

Sex of the foetus (M 2d > F)

Question 3

What time of day do mares most commonly foal?

Answer 3

b/w sunset + midnight

Question 4

Signs of impending parturition (+ when they present)

Answer 4

Udder oedema/enlargement (4wks pre-partum)
Relaxation of sacra-sciatic ligs (2wks)
Waxing colostrum (2-3d)
Increased milk [Ca] (1-2d)

Question 5

Stages of equine parturition + length of each stage

Answer 5

Stage I = preparation for birth (<12hrs)
Stage II = delivery of the foal (5-20mins)
Stage III = expulsion of foetal membranes (4-6hrs)

Question 6

What vaccinations are recommended for foaling mares + when?

Answer 6

Tetanus + strangles

single injection 4-6wks pre-partum

Question 7

Management practices involved in preparing the mare for foaling

Answer 7

Move mare into foaling units (wks) then foaling pen (days)
Open caslicks (last 2-4wks)
Observation of mares in foaling pens overnight (foal watch)

Question 8

Is induction of parturition common in mares?
What are some indications?
What is NOT an indication?

Answer 8

Very few indications - often causes foal death

Indications:

• Prepubic tendon rupture
• mare who has lost several foals at unassisted foaling
• mare w severe pelvic inlet compromise (fractures)

Prolonged gestation ≠ indication for induction
(overdue foals are small, rather than large)

Question 9

Criteria for maximal neonatal viability if inducing parturition

Answer 9

≥330d gestation
Some cervical relaxation (can admit ≥1 finger)
Udder development + colostrum present
[Ca] in colostrum ≥ 200 ppm

Question 10

Protocol for induction of parturition in mares

When should parturition begin after admin of the drugs?

Answer 10

OXT (10 IU IV) –> parturition begins w/in 10mins
> if water doesn’t break w/in 40mins > vaginal exam
> if straining for 10min w/o water breaking > incise chorioallantois
> if straining for 10min after water breaking > check for malpresentation/malposition

Question 11

Is low or high dose OXT indicated for inducing equine parturition?

Answer 11

Low dose (fewer complications)
- high dose OXT = dystocia, xs uterine contractions, red bag, foetal death, uterine prolapse/rupture

Question 12

What sign indicates stage I of parturition has begun + finished?

Answer 12

Start = uterine contractions
End = rupture of chorioallantois at cervical star

Question 13

What sign indicates stage II of parturition has begun + finished?

Answer 13

Start = rupture of chorioallantois at cervical star
End = expulsion of the foal

Question 14

What sign indicates stage III of parturition has begun + finished?

Answer 14

Start = expulsion of the foal
End = expulsion of foetal membranes

Question 15

What events occur during stage I of equine parturition?

What behavioural signs indicate a mare in stage I?

Answer 15

Uterine contractions
Positioning of foetus

Behavioural signs = restlessness, urination/defaecation, sweating, rolling

Question 16

Foetal + maternal causes of dystocia in horses

Answer 16

Foetal causes (more common) = malpresentation (incomplete rotation during stage I/II)
- shoulder lock/head flexion/limb flexion  >>> hip lock

Maternal causes = failure to push/primary uterine inertia (hypoCa)

Question 17

Consequences of dystocia & when they happen

Answer 17

Foals likely to die (if not expelled w/in 1hr of chorioallantoic rupture)
Trauma to birth canal

Question 18

Tx of dystocia

Answer 18

Get mare up & walking (= stops pushing TF stops foetal hypoxia)
Epidural (if manipulation will take time)
Clenbuterol = relaxes uterus

Question 19

What extra precautions/drugs must be given/taken if performing a foetotomy?

Answer 19

Restrain + sedate mare

Admin epidural

Question 20

What is a red bag delivery?
Is this an emergency?
What action should be taken?

Answer 20

Failure of the cervical star (chorioallantois) to rupture

True emergency > cut the chorioallantois + deliver foal ASAP

Question 21

Why does continued pushing by the mare present a risk to the foal if it is not being expelled?

Answer 21

Pushing = squeezes blood out of placenta > foetal hypoxia

Question 22

What is the clinical sign of red bag delivery?

Answer 22

Straining w/o making any progress
Presentation of the chorion (bright red) at the vulval lips, rather than the amnion (white)
Post-partum exam of membranes = torn in half

Question 23

What are some consequences of a red bag delivery?

Answer 23

Foal can’t be delivered (foal in bag + fluid = too big for canal)
Maternal pushing > foetal hypoxia
Membrane rupture elsewhere > fluid escapes but must tear right across before foal delivery possible > delivery w chorioallantoic hood > suffocation > death/hypoxia-induced cerebral damage (dummy foal)

Question 24

Treatment of peripartal haemorrhage

Answer 24

Confine the mare to prevent movement
Anti-fibrinolytic (tranexamic acid)
Hypertonic fluids (care not to overload)
Sedatives/analgesia
Prophylactic ABs > prevent secondary infection
± Blood transfusion

Question 25

Clinical criteria to Dx RFMs

Answer 25

Membrane retention beyond 4-6hrs post-foaling

Question 26

Consequences of RFMs in horses

Answer 26

Septic metritis > laminitis/sepsis/toxic shock/death

Question 27

Tx of RFMs

Answer 27

OXT (10 IU q45min)
BS ABs (penicillin + gentamicin)
± IV fluids if impaired renal fcn/dehydration/RFM > 12hr
NSAIDs
Careful manual removal - twist into a cord to prevent tearing + massage attachment area per-rectum
(NEVER USE FORCE)

After removal:

• Flush uterus (saline) until recovered fluid is clear
• OXT (10 IU q6h for 24h)

Question 28

What acute peri-partal conditions may present in mares?

Answer 28

Internal haemorrhage
External haemorrhage
Vaginal/vestibular lacerations
Perineal lacerations
Cervical lacerations
Uterine rupture

Question 29

Tx of vestibular/vaginal lacerations

Answer 29

Systemic ABs

Topical AB cream