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Three methods of oxytocin-induced parturition and their effects of foals
M L Macpherson1, M K Chaffin, G L Carroll
1Department of Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, College Station 77843-4475, USA.
Objective:
To compare effects of 3 oxytocin-based induction techniques on fetal and neonatal foals.
Design:
Prospective randomized controlled trial.
Animals:
16 pregnant mares.
Procedure:
Parturition was induced in mares by use of 3 treatments: group 1, 75 U of oxytocin, IM; group 2, 15 U of oxytocin, IM, q 15 minutes, for a maximum of 75 U; group 3, 75 U of oxytocin in 1 L of 0.9% NaCl solution IV (1 U/min), for a maximum of 75 U. Blood gas values and indices of vitality were measured in foals, and variables describing parturition were measured in mares.
Results:
Group-3 mares had a shorter interval from administration of oxytocin to rupture of the chorioallantois (OTCA) than group-2 mares. More foals were abnormal when the interval from oxytocin administration to delivery of the foal (OTDE) was > or = 60 minutes. Arterial blood gas values, measurements of vitality, and plasma cortisol concentrations did not differ among foals in various treatment groups. Increased interval for OTCA and OTDE resulted in higher neonatal PaCO2, and a longer interval for OTCA resulted in lower arterial pH. Time required for birth was shorter in mares with a dilated cervix. More abnormal foals than normal foals were delivered after premature placental separation or dystocia. Abnormal foals took longer to stand and suckle than normal foals. Interval from delivery to suckling was positively correlated with OTCA, OTDE, and PaCO2.
Clinical Implications:
Method of oxytocin-induced parturition did not impact neonatal outcome. Interval from induction until parturition, degree of cervical dilatation, and intrapartum complications influenced induction success.