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EQUINE VETERINARY EDUCATION / AE / JANUARY 2020
with the electrodes placed on the mare with one on dorsal midline, one on ventral midline and others placed on either side of the flanks. The fetal ECG should be able to be distinguished from the maternal ECG, which has larger, slower deflections (Vaala 2011). An alternative is a telemetric system such as the Televet 100,3 in which both maternal and fetal ECGS are obtained but with the use of software that identifies the maternal R waves, then extracts them from each event to leave a “cleaned” signal representing fetal R waves. Frequent monitoring of the ECG will allow the clinician to detect bradycardia or tachycardia, indicative of fetal demise or distress respectively. The presence of colostrum and the analysis of mammary
Fig 6: The CM Hernia Belt: commercial abdominal support bandage. Image courtesy of CM Equine Products2.
Broad spectrum antimicrobials are indicated to reduce
abscess formation within the haematomas (Rodgerson 2011). Progestin therapy is indicated to maintain uterine quiescence, and in the treatment of any accompanying placentitis.
Monitoring
Frequent monitoring of these mares is required, with particular noting of her pain status, and cardiovascular parameters. Mares close to foaling should have their mammary secretions monitored daily (in the evening) or twice daily, so that if deterioration of mare or foal occurs, the clinician is alerted to “fetal readiness for birth”. Maternal endocrine monitoring may be used to assess
fetal maturity, well being and impending parturition. A complete description is beyond the scope of this article but is well summarised by Vaala (2011). As a very brief overview, progestagens remain fairly constant until approximately 3 weeks prior to birth, when a gradual elevation should occur. If progestagens rise prior to this, placental compromise (such as placentitis) is likely. A significantly decreased level however is indicative of fetal compromise. Similarly, total oestrogens can be measured; the normal pattern is a peak at 7–8 months of gestation followed by a gradual decline. Low oestrogen levels prior to 9 months indicate fetal stress and compromise, though the sensitivity of this in late pregnancy may be reduced as severe fetal stress can occur before levels decline (Vaala 2011). Fetal monitoring is important to detect fetal stress, as this
may prompt intervention sooner. An in depth description of transabdominal ultrasonographic fetal monitoring is described by Reef et al. (1995). Briefly, daily transabdominal ultrasonographic examination of the fetus should be performed, assessing;
Fetal presentation (with transverse presentations indicating likely dystocia),
Fetal heart rate (with either bradycardia of <60 beats/min or tachycardia of >120 indicating fetal stress)
Fetal activity level (some degree of activity should be noted within a period of 30 min).
Fetal stress and viability can also be monitored via ECG examination. This can either be completed conventionally
© 2018 EVJ Ltd or posterior
secretions are an important indicator of fetal readiness for birth. It is proven and well accepted that when mares were induced to foal with calcium levels greater than 10 mmol/L the foal survival rate was better than those induced with a calcium lower than this (Ousey et al. 1984). The majority of mares with a calcium greater than 10 mmol/L also foal within 24–72 h (Card 2011). Sodium and potassium will also alter after the calcium levels rise, such that at the time of parturition mares should have a decreasing sodium and an increasing potassium, with inversion occurring around 30 mmol/L. A typical electrolyte profile of a mare due to foal imminently would be:
Ca >10 mmol/L Sodium ≤30 mmol/L Potassium ≥35 mmol/L
As such, this would be the desired electrolyte profile in amare
in which parturition is being induced. An adapted scoring system pertaining to calcium, sodiumand potassium concentrations has been devised to predict the likelihood of a positive outcome following induction (Table 1)(Ousey et al. 1984). It is preferable to use a laboratory analysis of mammary
secretion electrolytes as many stall side tests rely on the use of calcium alone. This is less accurate as elevated calcium may also be seen in cases of placentitis or twins (Paccamonti 2012). Water hardness kits are used in some clinics, and these are helpful tools but can be prone to inaccuracies as some measure calcium and magnesium; however magnesium may rise prior to calcium (Paccamonti 2012). Laboratory analysis of calcium, sodium and potassium together optimise accuracy. However, even with laboratory analysis of a full panel of electrolytes, the clinician should be aware that limitations will still exist, and a risk of inducing parturition in premature foals with lower survival rates remains. In addition to monitoring electrolytes, it has been reported
that a reduction in pH occurred in peri-parturient mares, and that twice daily determination of pH could effectively predict parturition (Korosue et al. 2013). This is valuable information,
TABLE 1: Scoring system for mammary secretion electrolyte concentrations (Ousey et al. 1984)
Calcium (mmol/L)
≥40 ≥7 ≥5
Sodium (mmol/L)
≤30 ≤50 ≤80
Potassium (mmol/L)
≥35 ≥30 ≥20
Total score ≥35 suggests a probable safe induction.
Points for each electrolyte
15 10 5
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