Experimental production of neonatal isoerythrolysis in the foal

Serological evidence with or without clinical signs of neonatal isoerythrolysis was experimentally produced in 6 of 8 foals born to mares allo-immunized with washed erythrocytes from the stallion. Blood group antigens were determined in all mares, stallions and foals, and the incompatible antigenic factor(s) responsible for the disease were defined. In 5 of 8 foals born to alloimmunized mares, a single antigenic factor difference accounted for the erythrocyte incompatibility between mare and foal. The erythrocyte antigen suspected as the most responsible for isoerythrolysis observed was A1. Agglutinin and hemolysin titers were measured in mare serum and colostrum. Of the presuckle anti-foal erythrocyte titers, colostral and hemolysins titers were greater than serum and agglutinin titers respectively. Foals were allowed to nurse and treatment of affected foals was not attempted which allowed full expression of disease and outcome.