Page 463 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

438 CHAPTER 2

VetBooks.ir 2.39 used in association with other assessment techniques
because there can be difficulties in obtaining and
interpreting the traces (Figs. 2.39, 2.40).
+
Amniocentesis
Amniotic and allantoic fluid can be obtained by this
technique. Research initially suggested that analysis
of these fluids might help in determining the matu-
– rity of the fetus, but it has no significant advantages
over less invasive procedures. It is carried out most
safely under ultrasound guidance, but there are sig-
nificant potential risks of abortion.

Changes in mammary secretions
The electrolyte levels in the secretions produced by
Fig. 2.39 Diagram showing the sites of attachment the mammary gland undergo characteristic changes
of the leads to the mare for a fetal ECG. during the last week of gestation (Fig. 2.41), spe-
cifically potassium and calcium concentrations rise,
2.40 while sodium concentrations fall. In a mare that is
ready to foal the milk will have the following compo-
P QRS T
sition: calcium >10 mmol/l; potassium >35 mmol/l;
sodium <30 mmol/l. Should these changes occur in
a mare prior to 310 days of gestation, they are sug-
gestive of placental pathology (placentitis or twin-
21 2 1 2 1 2 1 2 1 2 ning) and warrant investigation and appropriate
treatment as these mares are at an increased risk of
fetal abortion or early foaling. Caution should be
used in interpreting milk electrolyte levels in maiden
Fig. 2.40 Typical ECG traces of (top) a non- and pony mares and also in late-pregnancy mares
pregnant mare, (centre) a single pregnancy and that are ill, where maternal and fetal preparation for
(bottom) a twin pregnancy. Arrows indicate the fetal parturition may not be synchronous.
heart beat.
MANAGEMENT OF HIGH-RISK MARES

2.41
Sodium Identification of the high-risk pregnancy is para-
140 Potassium
120 Calcium mount if the pregnancy is to be given the chance
of continuing to term. Mares with high-risk preg-
mmol/l 100 nancies should be given treatment according to the
80
maternal disease present. Mares with placentitis
60 can be given systemic antibiotics based on culture
40 and sensitivity. Studies have shown that potenti-
20 ated sulphonamides, procaine penicillin, crystalline
penicillin and gentamicin can all, when admin-
0
16 14 12 10 8 6 4 2 0 istered systemically, cross the placenta and reach
Days before parturition therapeutic levels in the fetal fluids. However, the
Fig. 2.41 Mammary electrolyte secretions in the spectrum of action of procaine penicillin and crys-
mare. talline penicillin is limited and although gentamicin