Page 484 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Reproductive system: 2.1 The female reproductive tr act 459

VetBooks.ir decision to induce parturition: intravenous drip (60 IU in 500 ml saline) over
Several criteria need to be met prior to making a
15–60 minutes. Parturition usually starts within

• Greater than 330 days’ pregnancy. 30 minutes after intravenous administration. The
abdominal contractions and the whole foaling can
• Sacrosciatic ligaments and vulva should have be quite vigorous. Misoprostol directly onto the
some evidence of relaxation. cervix together with digital cervical dilation can
• Some cervical relaxation. be used to relax and dilate the cervix for delivery.
• Fetus in normal presentation, position and • Corticosteroids. High doses of dexamethasone
posture. intramuscularly every day for >4 days will cause
• Mammary secretion and analysis consistent the mare to foal, but there are significant risks
with fetal readiness for birth. There should be to the foal and mare with this technique and
colostrum in the udder. it is generally not recommended. This regime
• Milk electrolytes should be used to try and can be useful in helping to mature the fetus
predict fetal readiness for birth. There is an prior to birth in mares with significant medical
increase in calcium (>10 mmol/l [40 mg/dl]) or orthopaedic conditions that mean a normal
and potassium (>35 mmol/l [35 mEq/l]) and a gestational length is unlikely.
decrease in sodium (<30 mmol/l [30 mEq/l]) • Prostaglandin F α. Various forms of PGF α,
2
2
immediately before induction. including fluprostenol and cloprostenol, have
been used. It is ineffective if the mare is not ready
There are several methods of induction described to foal. The foaling can be rapid, with vigorous
in the literature, each having varying advantages and contractions, and there are reports of cervical
disadvantages: rupture and poor fetal viability following its use.

• Oxytocin. This is the method of choice in any Preparation for the delivery is paramount. Drugs
mare over 300 days’ gestation. Low doses of and equipment (including oxygen) for foal resuscita-
intravenous oxytocin (2.5–10 IU) will induce a tion should be available together with sufficient vet-
mare to foal (can be repeated every 15–30 minutes erinary staff to attend to the mare and foal separately
depending on progress). Other regimes include in case of complications. All induced foalings should
a single intravenous bolus (up to 20 IU) or an be attended by a veterinary surgeon.

DYSTOCIA

The incidence of dystocia is very low compared with more than 15 minutes without any clear progress in the
food animal species, but it does vary from breed to birth. In some cases, intervention may be unnecessary,
breed and is more common in the young, primiparous but a proper clinical assessment will allow problems to
mare. Thoroughbreds are thought to have an incidence be identified and action taken promptly.
of 4–5% compared with 8–12% for draught breeds and
Shetlands. Long fetal limbs and neck are usually the GENERAL TELEPHONE
cause of the problem and true fetal oversize is rare in ADVICE TO OWNER
the horse. Dystocia is one of the few true emergencies
in equine clinical practice. A very short period of time • Keep the mare walking. In the event of a
can be the difference between a live and a dead foal, as malposture, this will minimise straining and so
well as serious injury to the mare due to a combination reduce the likelihood of the foal being impacted
of powerful abdominal contractions and early separa- into the pelvic canal.
tion of the placenta. Most clinicians use the criterion • Place a clean tail bandage on the mare.
that clinical examination of a foaling case is justified if • If information suggests that the mare has a
the mare has been in the second stage of parturition for premature placental separation (red bag delivery),