Retained placenta in Friesian mares: incidence, risk factors, therapy, and consequences

This study concerns incidence, risk factors, therapy and consequences of retained placenta after normal foalings in Friesian mares. Retained placenta was defined as failure to expel all fetal membranes within 3 hours after the delivery of the foal. Incidence of retained placenta was studied in 495 parturitions. As possible risk factors for retained placenta, serum calcium, magnesium (n=155), and vitamin-E concentrations, and glutathion peroxidase activity in blood (n=99) were determined within 12 hours post partum and compared between mares with and without retained placenta. Age of the mare, sex of the foal, gestational length and recurrence of retained placenta were recorded and also compared between mares with and without retained placenta. As therapy, the relative effectiveness of intra venous administration of oxytocin in saline solution (n=59) and of oxytocin in a Ca-Mg-borogluconate solution (n=53) was studied. Parameters for post partum reproductive performance were compared between mares with (n=54) and without retained placenta (n=50), and within the group of mares with retained placenta, of mares from which the fetal membranes had been removed manually (n=30) and from which it was not (n=24). Incidence of retained placenta in Friesian mares was 54%. Mares which retained the placenta had lower serum calcium concentrations within 12 hours post partum than mares without retained placenta (P<0.05), whereas mean serum magnesium and vitamin-E concentrations, and glutathion peroxidase activity in blood showed no difference. Age of the mare, sex of the foal and gestational length were not different between mares with and without retained placenta. Mares which had retained the placenta after previous foalings, had a 2.9-fold increase of retained placenta. Sixty four percent of the mares treated with oxytocin in Ca-Mg-borogluconate solution responded positively to the treatment, compared to 44% of the mares treated with oxytocin in saline solution (P<0.05). Post partum reproductive performance did not differ between mares with and without retained placenta, and of the mares with retained placenta, between mares with and without manual removal of the placenta..