Foals are born without immunoglobulins (G) and must receive adequate antibodies from the mare’s colostrum.
Up to 20% of foals are subject to a total or partial deficit of  immune passive transfer. These animals are therefore at risk of infection, serious illness and even death. Failure of antibody passive transfer can occure as a result of premature lactation, deficient sucking, malabsorption, or low IgG levels in the maternal colostrum.

IgG levels should be measured approximately 12 to 24 hours after birth, since the intestinal mucosa of the newborn foal remains permeable to the passage of antibodies for a limited period of 24-48 hours.
An adequate level of IgG is about 800 mg / dL or higher: levels lower than 400 mg / dL indicate inadequate passive transfer and the need for additional IgG supplementation.
A rapid identification of the antibody titre is essential to for the early initiation of treatment of immunodeficient foals.