Milk electrolytes and induction of parturition

Abstract

Induction of parturition should not be viewed as a tool to make foaling more convenient but as a means by which proper veterinary care can be provided without delay when complications are anticipated. The best way to insure that veterinary assistance will be available when a mare foals is to induce parturition. However, because the equine gestation length is so variable, and inducing parturition before the foal is mature and capable of life outside the womb is an invitation for disaster, assessing fetal readiness for birth is paramount for achieving success. The best method to assess fetal readiness for birth is to measure calcium, sodium and potassium in the mammary secretions. A level of 10 mmol (400 ppm) calcium, in combination with a concentration of potassium that is greater than that of sodium, is indicative of fetal maturity. However, with pregnancies complicated by problems such as placentitis or twins, milk electrolytes are unreliable for assessing fetal readiness for birth. Nevertheless, milk electrolytes may still be helpful in these cases to decide when close supervision is recommended. Regardless, care must be taken to understand the testing method used and thereby interpret the results. Usually, when parturition is induced it is done so because a high probability of complications exists. Therefore it is recommended to place an intravenous catheter prior to the induction procedure. Similarly, planning for possible complications such as dystocia, premature placental separation or neonatal problems before beginning the induction procedure will greatly speed their successful resolution if encountered. Although many methods for inducing parturition have been reported, a single low dose of oxytocin (10 IU, i.v. for a 550 kg mare) is preferred. Provided the criteria for readiness for birth have been met, a single low dose is sufficient to initiate the cascade of events leading to parturition and provides a more natural course of events than higher doses or repeated administration.