When a foal is born it doesn’t have any antibodies capable of fighting infection. It can only get these antibodies by drinking the milk which the mare produces in the first 2 days after foaling. This milk is different to normal milk because it is full of all the antibodies the foal needs and is called colostrum.
If the foal does not receive these antibodies it will be extremely susceptible to infection and can become seriously ill. This is called failure of passive transfer. Sometimes the foal will receive some antibodies but maybe not enough for example if the mares milk does not contain the right amount; in this case the foal is still susceptible to infection and this is known as partial failure of passive transfer.
Anything which prevents the foal from sucking within the first few hours of life can cause failure of passive transfer, e.g.:
- If the mother rejects the foal and does not allow it to suck.
- If the foal is unable to latch on.
- If the foal has difficulty standing because it is already weak or because of conformational deformities.
- The mare may not produce enough colostrum.
- The colostrum may not be of good quality and the foal may not receive enough antibodies.
- The mare has been running milk prior to giving birth and all of the antibodies may have been lost in this milk.
It is important to observe the foal carefully and monitor it to make sure it has sucked properly after birth. If you are concerned at all you should contact your vet immediately.
If the foal becomes unwell in the first few days of life it may be that it is due to failure of passive transfer and your vet will take a blood sample to check the foals antibody levels.
If blood tests show that your foal has not received adequate antibodies or you know that it has not sucked there are several things your vet may do. If it is within the first 2 days of life and the mare has adequate, good quality colostrum the vet may take the colostrum from the mare and administer it to the foal via a stomach tube to ensure the foal receives it all.
If colostrum from the mare is not available a foster mare or commercial colostrum preparations may be used.
If the foal is very sick your vet may decide that it requires a plasma transfusion. Plasma is a component of blood containing lots of antibodies and can be bought commercially or harvested from the mares blood. It can be given to the foal through a vein for rapid administration of these important antibodies.
There are lots of ways to prevent and check for failure of passive transfer:
- If your mare starts running milk prior to giving birth this milk can be collected and frozen and then given to the foal when it is born.
- Foals should be monitored closely in the first few hours of life to make sure that they suck properly; it is however important to give the mare and foal time and space in order to bond.
- The foaling environment should be kept very clean so that the chances of the foal catching an infection are reduced.