In the sad event that a mare is unable to nurse her own foal it may be necessary to foster the foal onto a mare that is not its natural mother. This process requires very careful planning and should be arranged as soon as possible and before the foal is 3 weeks of age.
The foster mare will usually be a mare which has lost her own foal, but should also be one who is suitable. The mare must be vaccinated, healthy, have a quiet temperament, be well handled and ideally have experience in mothering foals. In addition, the mare must be producing the volume of milk necessary to nourish the foster foal. Mares for fostering are often advertised on social media sites or via The Foaling Bank.
Foals are born without natural protection from infection. At birth they receive this via colostrum, the first milk, which they must ingest within the first 18 hours of life. To be suitable for fostering, a foal should have received adequate colostrum, either from their own dam or from a donor source. This ‘transfer of passive immunity’ can be checked by taking a blood test from the foal at 24 hours to measure IgG levels, which should be over 800mg/dl. If this has not been achieved a plasma transfusion should be given. Foals suitable for fostering should also be strong, able to stand unassisted and to suck well.
Preparation of the mare for fostering is a delicate process. If the mare has recently lost her own foal she should be left in a stable with it and, if possible the placenta should be kept. Once the foal for fostering is ready the dead foal should be gently removed from the mare and skinned. The skin of the dead foal can then be used as a coat for the foster foal and, if available, the foal can be rubbed with the placenta, to transfer the dead foal’s smell.
The mare and foal should be introduced to each other in a large, clean stable. The mare should be deeply sedated and held using a bridle. It is helpful if the mare’s bag is not overfull, as this may make sucking painful for the mare. In addition, the foal should be hungry when first presented, to encourage sucking. The mare should be positioned in a corner of the stable and the foal introduced at her shoulder so that she can see and smell the new foal. The mare must be closely monitored; nickering and ‘talking’ to the foal would be an excellent reaction, but she will often behave aggressively and require further restraint to allow the foal to approach. The mare and foal should not be left alone at this stage, as some mares will wait for an unguarded opportunity to show aggression. It is helpful to allow the foal to move around the box at some distance from the mare to allow her to get used to the foal. Mare milk replacer or milk pellets should be available to supplement the foal.
It may take days before the fostering process is complete and in some cases an alternative foster mare may be required. It is vital that the mare and foal are not left unattended until there is complete confidence that the process has been successful. Fostering can be a very satisfying process, making the best out of a less than ideal situation. Orphaned foals that are raised on foster mares are easier to manage, healthier and better developed physically and mentally than hand-reared foals. However, if there is no mare available or the foal risks injury from an aggressive mare, then hand rearing an orphaned foal may be the only option.