Jaundice in Foal May Signal Serious Condition

A long-awaited foal has been born with no complications and is nursing strongly, getting important colostrum from the mare. However, by the next day the foal is weak and trembling. It has trouble breathing and its eye membranes have a yellowish color. The foal may be suffering from an uncommon but serious condition known as neonatal isoerythrolysis (NI) in which the foal’s red blood cells have been attacked by antibodies in the mare’s colostrum.

Normal colostrum is packed with antibodies that protect the foal from infection in the first weeks of life. In rare cases when a foal has inherited particular blood types from the sire and the mare’s blood becomes exposed to the foal’s blood (such as during placental hemorrhage), the mare produces antibodies against the foal’s red blood cells and passes them along in her colostrum. It’s also possible that a mare that has had a blood transfusion at some time in the past may have developed these dangerous antibodies.

Signs of illness in the foal may be seen in the first twelve hours after birth or over the course of several days. Yellowing of mucous membranes (jaundice) is caused by the byproducts of red blood cell destruction. Weakness, trembling, and shortness of breath are signs that oxygen normally transported by red blood cells is not reaching the brain and other body tissues. Lack of oxygen can damage the liver, kidneys, and brain cells.

Treatment should begin as soon as the condition is diagnosed. Oxygen therapy and blood transfusions are sometimes used. The foal must not be allowed to ingest more colostrum from its dam, though colostrum from another mare can be given to provide immunity to infection. The mare should be milked out for 24 hours to remove all colostrum, after which the foal can be allowed to nurse normally.

Testing the mare’s blood a few weeks before her expected delivery date can identify an anticipated problem. Tests can also be performed to see if the foal’s blood and the mare’s colostrum are compatible. A veterinarian should test the foal’s blood in any case to be sure that it has gotten an adequate supply of antibodies for protection against disease.