Foals are born with a naive immune system, and rely upon the ingestion and absorption of immunoglobulins from the dam's colostrum to obtain passive immunity. Failure of passive transfer (FPT) is the most common immunodeficiency disorder in the horse and is associated with an increased risk of infectious disease and mortality. Routine screening is recommended, to allow early detection and treatment. Management of failure of passive transfer is dependent on the age of the foal at the time of diagnosis, but primarily involves intravenous plasma administration or the administration of colostrum (orally or via nasogastric intubation). Given the association between IgG concentration and clinical outcome, early detection and management of FPT are important in reducing morbidity and mortality in neonatal foals.