Fostering of foals

When faced with an orphan foal, due to the death of the mare or her unwillingness to accept her foal, it is critical to quickly find an alternative way to feed the foal and create a suitable social environment for its upbringing. One can use a mare that has recently lost her own foal as foster mare; however, when a suitable adoption mare cannot be found or when the mare does not want to adopt the new (unknown) orphan foal, other options must be considered including feeding a replacement formula or using a mare with induced lactation. Today, there are excellent milk replacements that enable us to feed an orphan foal for a limited time or even up to weaning age with excellent body development. However, prolonged bottle feeding often results in poor social skills towards other horses and abnormal/dangerous behaviour towards humans. With simple and relatively safe methods available for inducing lactation and fostering foals to mares, it seems advisable to recommend the use of this type of foster mare to owners. Induction of lactation is described in another abstract presented at this meeting. Initially, our method for adoption consisted of a system whereby the foal was presented to the adopting mare while the anterior vagina and cervix of the mare were vigorously massaged, triggering oxytocin release through the Fergusson reflex which in turn triggers maternal behaviour in the brain. The administration of large doses of oxytocin does not trigger maternal behaviour because oxytocin does not cross the blood–brain barrier; in contrast, a large dose of PGF2α does initiate maternal behaviour, presumably through the stimulation of central oxytocin release within the brain. Careful observation of behaviour in normal mare–foal combinations and in adopted combinations demonstrate that the bonding and interaction between mare and foal are identical.

Adoption technique

The mare must have raised a foal in the past but must not have foaled and/or been weaned in the current breeding season. Lactation will have been successfully induced using the methods described elsewhere in these proceedings and the mare is ready for adoption when the milk production has reached at least 2–3 L per day (usually after 5–7 days of treatment).
Preferably, the mare has been housed in a calm, rather isolated location for the past days or weeks so that she feels safe in her box. It is also advised that she has no direct contact with neighbouring horses that may be seen as a threat to the foal during the adoption process. Some veterinarians have suggested that the foal should be in an adjacent stall in the days prior to the adoption so that both can become familiar with each other. However, we have not added this to our protocol and have not seen a need to do this.
On the day of the adoption, the foal is not fed during the 1–2 h prior to the adoption to ensure that it is hungry and motivated to seek the udder of the mare. Immediately before the foal and mare are brought together for the adoption, maternal behaviour needs to be triggered; this is no longer induced by vaginal massage, but by a single injection of PGF2α. We routinely use cloprostenol injected i.m. at 3–4 times the normal luteolytic dose (750–1000 µg cloprostenol or 3–4 mL Estrumate®). About 15–20 min after PGF2α injection, when the mare is starting to sweat and show other PGF2α-induced side effects (restlessness and signs of colic), the foal is moved to the mare’s stall, carefully introduced to the mare and gradually allowed to nurse. Usually when the foal is introduced, the mare will immediately start to lick and nuzzle the foal and will often vocalise in a similar way to a mare that has just delivered and is making first contact with the newborn foal. The foal should be encouraged to nurse during the phase of PGF2α-induced side effects, while the mare is restrained sufficiently to allow the foal to nurse, but not to the extent that it would limit her licking and smelling the foal. Maternal behaviour is considered to be activated when the mare follows the foal around the stall, vocalises to communicate with it and licks it. Once maternal behaviour is established, both mare and foal can circulate freely in the stall and continue the bonding process. Complete adoption of the foal by the mare is usually accomplished within 20–30 min after introduction of the foal.
In fewer than 5% of attempts, maternal behaviour is not initiated and the mare refuses the foal. This becomes apparent within 5–10 min of the introduction of the foal and the foal should then be removed as the mare may become increasingly aggressive. In our experience, mares that fail to adopt should be retried 12 h later using exactly the same protocol (including PGF2α treatment) as this is nearly always successful in our hands.
In our clinical setting, the lactation is induced by twice-daily administration of sulpiride, a dopamine antagonist. The detailed description of the hormonal treatment for induction of lactation is the subject of another abstract in these proceedings. We recommend that the treatment for induction of the lactation is continued for 7–10 days after adoption. All client-owned foals are supplemented with artificial milk 3–5 times per day (1–2 L each time) for 3–15 days after adoption. Bottle feeding is continued until the foal refuses the artificial milk or when it is judged that the mare is producing sufficient milk. Although we have never been able to quantify weight gain in these foals nor to evaluate the impact of these interventions objectively, we have noted a very high client satisfaction rate.
Videos shown during the presentation can be viewed on YouTube:
https://youtu.be/YohQmwxajgk
https://youtu.be/s7d0hWbKMo4
https://youtu.be/cePBFV4EPRU
https://youtu.be/KoAW05QG1sU