The control of the reproduction in pregnant mares and the management of the early postpartum period - Literature review

SUMMARY The authors review the different pharmacological methods which were ever used to modify the reproduction in a pregnant mare and the reproduction in the early postpartum period. The reproduction key points of these periods are: the recognition of the symptoms lead to early embryonic death, the management of abnormal embryonic development, induction of an abortion, induction of a parturition and the management of the postpartum period. The earliest ultrasonographic symptoms which could emphasize a forthcoming early embryonic death (15–17 days post-ovulation) are the uterine oedema. This could be sometimes combined with behavioural oestrus. Some of these pregnancies can be salvaged by immediate administration of altrenogest. The mares with signs of abnormal embryonic development have to be re-examined at 1 to 3 days intervals. If an embryo and its heartbeat can not be identified ultrasonographically by day 30, than PGF2αshould be administered to induce luteal regression and return to oestrus for rebreeding. There are many methods to induce an abortion depending on the stage of parturition but it has to be performed so early as it can minimize the stress for the mare and for the owner, as well. A successful induction of par-turition in a healthy mare is based on the maturity of the foetus and the used method. The criteria for maturity of the foetus are: the presence of good quality colostrum with a high calcium content (> 10 mmol/l), the length of the gestation period (> 335 days) and the softening of the cervix. There are many methods (glucocorticoids, oxytocin, prostaglandins) which were ever tried to induce parturition but the frequent low doses or slow drop infusion of oxytocin proved to be more reliable. The pregnancy rate from foal heat breedings is higher in the mares that ovulate after 10 days postpartum compared with those that ovulate before this time. There are two methods used at this time to postpone breeding in the postpartum period until normal pregnancy rate can be achieved: to delay the onset of the foal heat or to shorten the interval to the second postpartum oestrus