Neonatal isoerythrolysis in foals

There is a rare condition called Neonatal isoerythrolysis (NI) where the foal develops antibodies against its own red blood cells, which are then destroyed. If left untreated, the foal will die.

First signs are often seen 48-72 hours after foaling when the foal starts to be lethargic, and possibly yawns more than normal. Blood testing will indicate low red blood cell content. If undetected, the foal will start to exhibit signs of jaundice, with the whites of the yes, the gums and other membranes becoming yellow. If there is any question of NI being a possibility, but antibody levels in the mare were not checked, then after birth (and before nursing), a sample of blood can be taken from the foal and colostrum from the mare, and a “Jaundiced Foal Agglutination Test” performed to determine if there are antibodies in the colostrum.

Pregnant mares can be checked during late term for presence of antibodies in their blood, and if detected, the foal should be prevented from nursing at birth and for up to about 72 hours after (obviously colostrum and milk must be bottle fed from another source), by using a muzzle.  Meanwhile, milk the dam to maintain milk production, and after  72 hours, the muzzle can be removed and the foal permitted to nurse from the dam.

Being aware of incompatible blood groups between the sire and dam is a starting point, as certain groups will be more likely to result in this problem. It is more commonly seen in second or subsequent foals rather than first foals.