Update on passive transfer of immunoglobulins in the foal

Abstract

Foals are born essentially agammaglobulinemic and rely on the absorption of colostral IgG for protection against infectious agents during the first few weeks of life. A mare produces colostrum during the last 2 to 3 weeks of gestation and once the foal suckles, it is rapidly depleted. Colostral quality is directly related to its specific gravity and the amount of immunoglobulin it contains can be estimated with an equine colostrometer or sugar or alcohol refractometers. Foals whose dams do not have adequate colostrum need to be supplemented with a substance rich in immunoglobulin. Equine colostrum is highly preferred as a substitute over bovine colostrum or commercial immunoglobulin products because the IgG is most readily absorbed. Failure of passive transfer can be estimated in the foal as early as 8 to 10 hours of age. There are a variety of assays that may be used in the field to rapidly estimate the immunoglobulin content in the foal. Foals with low serum IgG concentrations should receive additional IgG within the first 3 days of life. The well-being of foals with failure of passive transfer will depend greatly on the farm environment. Foals living in a clean, well ventilated barn that is not crowded are less likely to become ill than foals born into dirty, crowded conditions.