Part 2: Induction of
foaling in mares
What is induction of foaling?
This involves interfering with the natural foaling process by bringing it forward in advance of the due date. Drugs are given to the mare in order to try to cause this required effect which is hoped to happen within a few hours or days of giving the mare the drugs. My mare is three weeks overdue the foaling date, should she be induced?
No. As already mentioned, an overdue mare does not necessarily mean that the foal will become oversized.Therefore unless the mare has a major health problem, we do not induce her.In contrast to this, induction in cows is a procedure that is carried out quite regularly, to prevent oversize resulting in calving problems. In cows it carries very few if any complications generally. In fact in some of these cases, it may prevent problems especially when it is done early to prevent a longer pregnancy and a consequential oversized calf.However, induction of the birth of the offspring in mares can carry many complications and is only done in an extremely limited number of cases and only on exceptional grounds.What are the indications for induction in the mare?
Prolonged gestation, up to 390 days, is not an indication for induction.The fact that the mare is carrying ‘over her time’ is never a reason for induction.Mares going over a year in gestation are not that uncommon and not usually associated with problems, provided no other health problems are present.The following are main reasons where induction of a foaling may be considered: Where the mare is toxic and very unhealthy.If the mare has extremely sore feet and unable to carry the weight of the foetus inside. In these cases, the mare’s feet are so painful that she tends to lie down and could be unable to rise, e.g. a mare with chronic laminitis.A mare with severe ventral oedema or fluids along the abdomen and legs and is unable to move even with veterinary medication treatments.At what stage of pregnancy would induction likely to be attempted?
The mare should be at least 325 days into her gestation and longer if possible. She should have some udder/mammary development – i.e. milk to feed the newborn foal. It would always be preferable if she had some colostrum or ‘beastings’ to provide the foal with the required immunity for a healthy start to life.How is induction of a foaling carried out?
Due to the high level of risk of complications developing in both the mare and the foal, any methods used for induction must only be carried out by a veterinary surgeon.The treating veterinary surgeon may choose one or either of the following, if the rare decision is taken to induce a foaling: a) The veterinary surgeon may give high doses of oxytocin by intramuscular injection. However this has a prolonged time to delivery and causes the mare quite a considerable amount of discomfort.
b) In certain circumstances, the treating veterinary surgeon may use high doses of PG2 (Prostaglandins) but this has to be restricted to cases where the mare is near her due time. The foaling after this inject can vary in time from four-six hours to 48 hours.
c) In certain cases, the veterinary surgeon may decide to give low doses of oxytocin intravenously. The mare may start to foal within 20 minutes of this injection.
On a general basis, the closer the mare is to her ‘time’, the quicker she will foal after the induction injection.What types of complications can occur in induction of foaling?
There is a high risk of complications developing where the mare is induced. The most commonly seen problems that are likely to arise include:a) Prematurity in the foal, (e.g. in immaturity of the foal’s respiratory system).
b) Dystocia or foaling complications, (e.g. in malpresentation of the foal).
c) Failure of passive transfer of immunity from dam to offspring.
d) Retained placenta in the mare.
In the normal foaling, the foetus is initially upside down and just prior to the birth, it rotates inside the mare before parturition. In an induced mare, this rotation may not occur. This results in a presentation of an ‘upside down’ foetus, which requires immediate manipulation to get a live foal out on the ground.On a general basis, premature foals have a lesser chance of survival.The induced mare may have little or no milk. However provision can be made before the induction, to have frozen colostrum available from another source.Due to the extra oxytocin administered, there is a risk that the mare could also prolapse the uterus after expulsion of the foetus.Due to the above risks, induction is only carried out when it is considered to be a solution in an emergency type of case.Where it has to be carried out, the veterinary surgeon will consider all factors in order to try to minimise the risks and so will try to be sure that a) the foetus is mature enough to survive and b) that the mare is prepared and as ready as possible to cope with the given circumstances.Are there any precautions or checks that can be done to establish these important factors before induction is undertaken by the vet?
There are some preparatory basics that can be put in place to help reduce risks and problems associated with induced foaling/parturition, but results are variable.Some veterinary surgeons may use the following test to help to identify foal prematurity, i.e to establish whether or not the foetus is mature enough to survive. This commercially produced basic test kit is said to work on the following principles: The test utilises the correlation between changes in the electrolyte concentrations in the mammary secretions and the foal’s maturity. As the mare gets close to foaling, the amount of calcium increases in her milk. It is claimed that the test can predict foaling due dates by assessing the relative amounts of milk electrolyte concentrations (calcium, sodium, potassium, etc). The milk test results are variable and its accuracy is dependent on the kit and the experience of the individual reading these tests, so the test is not commonly used. It is just another “tool” that could possibly be used, in addition to the other signs etc, to assess immaturity in the foetus.Also it is important to remember that where a mare is short on colostrum, as could be the case in a mare considered for induction, it is best to avoid reducing her volume of colostrum, in the interest of maximising the volume for immunity transfer from the dam to the newborn foal.